Sensing device

Abstract

A sensing device according to one embodiment of the present technology includes an antenna unit, a power generation unit, and a sensing unit. The antenna unit is provided in the vicinity of a high-voltage line for power transmission, is connected to a first conductor and a second conductor that generate a potential difference therebetween, and forms an antenna by the first conductor and the second conductor. The power generation unit harvests the output of the antenna unit as power. The sensing unit is driven by the power from the power generation unit, and performs a detection operation for detecting, using a predetermined sensor, the state of a related facility or a surrounding environment of the high-voltage line.

Description

Sensing Device

[0001] The present technology relates to a sensing device that can be applied to remote monitoring of high-voltage lines and related facilities.

[0002] Conventionally, methods for remotely monitoring high-voltage lines that transmit power and facilities related to high-voltage lines have been developed. For example, Patent Document 1 describes a monitoring device for monitoring power transmission lines. This monitoring device is provided with a photographing unit that photographs the monitored object, a measuring unit that measures meteorological data such as the temperature and wind speed around the monitoring device, and a control device equipped with a communication unit. The monitoring device is also powered by a solar panel (see, for example, paragraphs

[0037] ,

[0038] ,

[0042] ,

[0048] , and FIG. 5 of the specification of Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-184817

[0004] As mentioned above, when a solar cell is used as the power source for a monitoring device, it is possible that sufficient power may not be obtained depending on weather conditions or the time of day, which could result in unstable monitoring of high-voltage lines. For this reason, there is a demand for technology that can stably detect the status of high-voltage line-related equipment and the surrounding environment.

[0005] In view of the above circumstances, an object of the present technology is to provide a sensing device that can stably detect the state of high-voltage line-related equipment and the surrounding environment.

[0006] To achieve the above object, a sensing device according to one embodiment of the present technology includes an antenna unit, a power generation unit, and a sensing unit. The antenna unit is connected to a first conductor and a second conductor, respectively, that are provided near a high-voltage power line for transmitting electricity and generate a potential difference between them, and the first conductor and the second conductor form an antenna. The power generation unit harvests the output of the antenna unit as power. The sensing unit is driven by power from the power generation unit and performs a detection operation to detect the state of equipment related to the high-voltage line or the surrounding environment using a predetermined sensor.

[0007] In this sensing device, a first conductor and a second conductor, which are installed near a high-voltage power line and have a potential difference between them, are used as an antenna, and the output of the antenna is harvested as power. This power is used to perform a detection operation in which a predetermined sensor detects the state of the high-voltage line-related equipment and the surrounding environment. This makes it possible to stably detect the state of the high-voltage line-related equipment and the surrounding environment.

[0008] The sensing unit may include a control unit that controls the detection operation, and a communication unit that performs communication related to the detection operation.

[0009] The sensing unit may include the predetermined sensor.

[0010] The antenna unit may include a protection circuit disposed between the power generation unit and an antenna formed by the first conductor and the second conductor, for protecting the power generation unit from a lightning surge.

[0011] The protection circuit may include a transformer or a fuse.

[0012] The power generating unit may include a power storage element that stores power harvested from the output of the antenna unit. In this case, the sensing unit may be driven by power from the power storage element.

[0013] The sensing unit may detect whether or not power is being transmitted through the high-voltage line based on a state of power harvesting in the power generation unit, and transmit the detection result to an external device.

[0014] The voltage of the high voltage line may be 500V or more.

[0015] At least one of the first conductor and the second conductor may be a metal body that constitutes an equipment related to the high-voltage line.

[0016] The sensing device may further include an antenna element provided near the high-voltage line. In this case, the first conductor may be the antenna element. The second conductor may be a metal body constituting the related equipment.

[0017] The antenna element may be a rod antenna, a cable antenna, or a ground member connected to earth ground.

[0018] The antenna length of the antenna element may be set so that the power output from the antenna unit is equal to or less than a predetermined threshold.

[0019] The high-voltage line may be a transmission line supported by a steel tower. In this case, the second conductor may be the steel tower. The first conductor may be an antenna element provided so as to be electrically floating from the steel tower. The predetermined sensor may detect the state of a power transmission facility including the power transmission line and the steel tower, or the state of the surrounding environment of the power transmission facility.

[0020] The high-voltage line may be an electric train line that supplies power to a train. In this case, the second conductor may be a metal part of the train. The first conductor may be an antenna element provided on the train so as to be electrically floating from the metal part of the train. The predetermined sensor may also detect the running state of the train or the state of the surrounding environment of the train.

[0021] The high-voltage line may be an electric train line that supplies power to a train. In this case, the second conductor may be a rail on which the train runs. The first conductor may be either an antenna element electrically floating from the rail that serves as the second conductor, or another rail different from the rail that serves as the second conductor. The predetermined sensor may also detect the state of wayside facilities including the rail or the state of the environment surrounding the wayside facilities.

[0022] The high-voltage line may transmit AC power. In this case, the power generation unit may include a rectifier circuit that rectifies AC received power induced between the first conductor and the second conductor by the AC power.

[0023] The high-voltage line may transmit DC power. In this case, the power generation unit may include a storage circuit that stores received DC power that flows due to a potential difference induced between the first conductor and the second conductor by the DC power.

[0024] The power generation unit may have a rectifier circuit that rectifies AC power output from the antenna unit and is configured to supply output from the rectifier circuit to a load element. In this case, the sensing device may further include a transformer connected between the antenna unit and the rectifier circuit, for matching impedance between the antenna unit and the power generation unit including the load element in a target frequency band in which a reduction in output power of the antenna unit when the power generation unit including the load element is connected to the antenna unit exceeds a predetermined threshold with respect to power corresponding to the open-circuit voltage of the antenna unit.

[0025] The load element may be either the sensing unit or a power storage element provided in the power generation unit for driving the sensing unit.

[0026] The predetermined threshold may be 30% of the power corresponding to the open circuit voltage.

[0027] 10 is a schematic diagram showing a configuration example of a sensing system including a sensing device according to a first embodiment of the present technology. FIG. 11 is a schematic diagram illustrating energy harvesting using a high-voltage line that transmits AC power. FIG. 12 is a block diagram showing a configuration example of a sensing device. FIG. 13 is a circuit diagram showing a configuration example of a rectifier circuit. FIG. 14 is a table showing the forward voltage Vf and reverse current Is of a rectifier diode. FIG. 15 is a graph of I-V measurement for the rectifier diode shown in FIG. 5. FIG. 16 is a schematic circuit diagram showing a configuration example of a storage circuit. FIG. 17 is a circuit diagram showing an example of a protection circuit against a lightning surge. FIG. 18 is a circuit diagram showing another example of a protection circuit against a lightning surge. FIG. 19 is a schematic diagram showing a configuration example of a sensing device according to a second embodiment. FIG. 19 is a block diagram showing a configuration example of the sensing device shown in FIG. 10. FIG. 19 is a schematic diagram showing a configuration example of a sensing device according to a third embodiment. FIG. 12 is a block diagram showing a configuration example of the sensing device shown in FIG. 13. FIG. 19 is a schematic diagram showing an example of a connection between a sensing device and a rail. FIG. 20 is a schematic diagram showing another example of a connection between a sensing device and a rail. FIG. 21 is a block diagram showing a configuration example of a sensing device according to a fourth embodiment. 28 is a schematic diagram illustrating energy harvesting using a high-voltage line for transmitting DC power. FIG. 29 is a schematic circuit diagram illustrating an example of the configuration of a power storage circuit. FIG. 30 is a block diagram illustrating an example of the configuration of a sensing device according to a fifth embodiment. FIG. 31 is a circuit diagram illustrating an example of the configuration of a sensing device. FIG. 32 is a circuit diagram illustrating a power harvesting device as a comparative example. FIG. 33 is a graph illustrating the frequency spectrum of noise from a fluorescent lamp. FIG. 34 is a circuit diagram illustrating an example of a measurement of the generated voltage across a load element. FIG. 35 is a schematic diagram illustrating characteristics when the internal resistance of a noise power source model is a simple resistance. FIG. 36 is a schematic diagram illustrating characteristics when the internal resistance of a noise power source model has a complex component. FIG. 37 is a graph illustrating the frequency characteristics of the voltage ratio when the resistance value of the load element in FIG. 24 is changed. FIG. 38 is a circuit diagram illustrating another example of a measurement of the generated voltage across a load element. FIG. 39 is a graph illustrating the frequency characteristics of the generated voltage when the resistance value of the load element in FIG. 28 is changed. FIG. 39 is a circuit diagram illustrating an example of a measurement of the generated voltage across a load element connected to a noise power source. FIG. 30 is a graph illustrating the waveform of the generated voltage when the resistance value of the load element in FIG. 30 is changed.30. FIG. 31 is a graph showing the frequency characteristics of the generated voltage when the resistance value of the load element in FIG. 30 is changed. FIG. 32 is a circuit diagram illustrating impedance mismatch in a comparative power harvesting device. FIG. 33 is a circuit diagram showing an example configuration of a power harvesting device equipped with a transformer. FIG. 34 is a schematic diagram showing an example configuration of a transformer. FIG. 35 is a circuit diagram showing an example configuration of a power harvesting device using a single transformer. FIG. 36 is a circuit diagram showing an example configuration of a power harvesting device using three transformers. FIG. 37 is a graph showing the charging characteristics of a secondary battery using a power harvesting device. FIG. 38 is a graph showing the discharging characteristics of a secondary battery charged by a power harvesting device. FIG. 39 is a schematic diagram showing an example configuration of a sensing device according to a sixth embodiment. FIG. 39 is a schematic diagram showing an example configuration of a sensing device with surge protection. FIG. 39 is a schematic diagram showing an example configuration of a sensing device according to a seventh embodiment. FIG. 39 is a schematic diagram showing an example configuration of a sensing device with surge protection. FIG. 39 is a schematic diagram showing an example configuration of a sensing device with surge protection. FIG. 39 is a schematic diagram showing an example configuration of a sensing device with rail protection.

[0028] Hereinafter, embodiments of the present technology will be described with reference to the drawings.

[0029] 1 is a schematic diagram showing an example configuration of a sensing system including a sensing device according to a first embodiment of the present technology. The sensing system 120 is a system that detects the state of related equipment 5 of the high-voltage line 1 and the surrounding environment using sensing devices 100 arranged around the high-voltage line 1 for power transmission. The sensing system 120 has at least one sensing device 100 and a management device 110.

[0030] The sensing device 100 is a sensor terminal in the sensing system 120. The sensing device 100 is provided with a status sensor 26 that detects the status of related equipment 5 of the high-voltage line 1, and a communication unit (see FIG. 3) that communicates with the outside. In the example shown in FIG. 1, a camera sensor is schematically illustrated as an example of the status sensor 26 provided in the sensing device 100. Note that other sensors can also be used as the status sensor 26. The status sensor 26 corresponds to a predetermined sensor.

[0031] The management device 110 is a data terminal for monitoring the detection results of each sensing device 100. The management device 110 receives, for example, the detection results of the status sensors 26 from each sensing device 100, and generates and displays a monitoring image or the like showing the detection results.

[0032] Wireless communication is typically used for data communication with the sensing devices 100. Each sensing device 100 is connected to a predetermined network by wireless communication with, for example, a base station (not shown), and communicates with the management device 110 via the network. Alternatively, for example, the sensing device 100 may upload data to a server device connected to the network, and the management device 110 may read the data from the server device. This makes it possible to realize a remote monitoring system that monitors the status of equipment 5 related to the high-voltage line 1 from a remote location.

[0033] The sensing device 100 includes a mechanism for harvesting the energy of the electric field formed around the high-voltage line 1 by the power transmitted by the high-voltage line 1, and operates using the harvested power. In other words, the sensing device 100 can be said to be a device equipped with an energy harvester that generates electricity from the environment by utilizing the electric field energy of the high-voltage line 1.

[0034] In this embodiment, a sensing device 100 is applied to a high-voltage line 1 that transmits AC power. That is, the sensing device 100 is configured to be able to harvest, as power, the electric field energy of an AC electric field formed by AC power flowing through the high-voltage line 1. A method for harvesting the electric field energy of an AC electric field as power will be described below.

[0035] Fig. 2 is a schematic diagram illustrating energy harvesting using a high-voltage line that transmits AC power. Fig. 2 shows a high-voltage line 1 that transmits AC power and two conductors that serve as antennas that receive electric field energy from the high-voltage line 1. Hereinafter, one of the two conductors will be referred to as a first conductor 11 and the other as a second conductor 12.

[0036] The first conductor 11 and the second conductor 12 are both conductors that are not electrically connected to the high-voltage line 1, i.e., conductors that float from the high-voltage line 1. Metal bodies are typically used as the first conductor 11 and the second conductor 12. Here, the conductor on the upper side in the figure is the first conductor 11, and the conductor on the lower side is the second conductor 12. Note that Figure 2 does not limit the positional relationship between the high-voltage line 1, the first conductor 11, and the second conductor 12.

[0037] The first conductor 11 and the second conductor 12 are provided near the high-voltage line 1. In the present disclosure, the vicinity of the high-voltage line 1 refers to, for example, an area in which it is possible to harvest the power required for the operation of the sensing device 100 from the electric field formed by the high-voltage line 1. This is an area in which capacitive coupling is obtained between the high-voltage line 1 and each conductor, allowing the required power to be harvested.

[0038] Furthermore, a potential difference occurs between the first conductor 11 and the second conductor 12. That is, the first conductor 11 and the second conductor 12 are not short-circuited to each other, and each can have an independent potential. Therefore, the capacitive coupling between the first conductor 11 and the high-voltage line 1 and the capacitive coupling between the second conductor 12 and the high-voltage line 1 are separate couplings.

[0039] In this way, the first conductor 11 and the second conductor 12, which generate a potential difference between them, each function as an antenna element that generates an AC current when subjected to the AC electric field 60 formed by the high-voltage line 1 (AC power). As a result, AC power corresponding to the AC electric field 60 is generated between the first conductor 11 and the second conductor 12. In other words, the first conductor 11 and the second conductor 12 form an antenna that receives the electric field energy of the AC electric field 60. Hereinafter, the power received by the antenna may be referred to as received power.

[0040] In the example shown in Fig. 2, the second conductor 12 is grounded to the earth ground 4. In this case, an antenna with a monopole structure is configured, with the second conductor 12 being grounded. On the other hand, if neither the first conductor 11 nor the second conductor 12 is grounded, an antenna with a dipole structure is configured. In either the monopole structure or the dipole structure, each conductor functions as an antenna element, making it possible to receive electric field energy of an AC electric field and output AC received power.

[0041] In this way, the antenna formed by the first conductor 11 and the second conductor 12 functions as an AC power supply 61 that outputs AC received power. In the sensing device 100, the AC received power output from the antenna (AC power supply 61) is rectified to DC by a rectifier circuit 20, which will be described later, and then harvested.

[0042] Next, a high-voltage line 1 to which the sensing device 100 is applied will be described. As shown in FIG. 1 , in this embodiment, the high-voltage line 1 is a transmission line 2 supported by a steel tower 6. The transmission line 2 is an overhead line for transmitting electricity that is fixed to the steel tower 6 via an insulator such as a porcelain insulator. Such a transmission line 2 is used, for example, to transmit electricity between a power plant and a substation, or between substations. The transmission line 2 is an example of the high-voltage line 1 in the present disclosure, and the steel tower 6 supporting the transmission line 2 is an example of related equipment 5 for the high-voltage line 1.

[0043] Generally, alternating current is used for power transmission using the power transmission line 2 supported by the steel tower 6. That is, the power transmission line 2 (high voltage line 1) transmits AC power. The AC power transmitted through the power transmission line 2 is typically three-phase AC, but single-phase AC or the like may also be used.

[0044] For example, in the case of three-phase AC, three high-voltage lines 1 form one set, and AC power is transmitted with a phase difference of 120 degrees. In the example shown in Fig. 1, two sets of power transmission paths are formed, one on the left and one on the right. The power transmission lines 2 constituting each phase may be single wires or multiple wires.

[0045] The voltage of the power transmission line 2 is generally set to between several tens of kilovolts and several thousand kilovolts (for example, 33 kV, 66 kV, 77 kV, 110 kV, 154 kV, 220 kV, 500 kV, 1000 kV, etc.). By using a power transmission line 2 with such a very high voltage, it is possible to significantly increase the amount of harvestable power.

[0046] Next, we will explain the antenna (first conductor 11 and second conductor 12) that receives electric field energy from the power transmission line 2. In this embodiment, the conductors that make up the antenna that receives electric field energy are an antenna element 10 provided near the power transmission line 2 (high-voltage line 1) and a metal body that makes up the related equipment 5 of the power transmission line 2 (high-voltage line 1). Here, the antenna element 10 corresponds to the first conductor 11, and the metal body that makes up the related equipment 5 corresponds to the second conductor 12.

[0047] The antenna element 10 is a conductive member that functions as an antenna element and is configured as an external antenna or an internal antenna of the sensing device 100.

[0048] The related facilities 5 of the power transmission line 2 are various facilities required for power transmission via the power transmission line 2. For example, the steel tower 6 supporting the power transmission line 2 is the related facilities 5 (power transmission facilities) of the power transmission line 2. Protective facilities such as fences installed around the steel tower 6, and power distribution facilities are also included in the related facilities 5. There are no other limitations on the types of the related facilities 5. In the sensing device 100, metal parts and structures installed in such related facilities 5 are used as conductors that make up the antenna.

[0049] As shown in Fig. 1, in this embodiment, a steel tower 6 is used as the metal body (second conductor 12) constituting the related facility 5. A plurality of ground electrodes are buried in the base of the steel tower 6 to avoid charging due to electrostatic induction of the power transmission line 2, for example. Therefore, the steel tower 6 becomes a conductor grounded to the earth ground 4. This makes it possible to easily configure a relatively large antenna element grounded to the earth ground 4.

[0050] Furthermore, the antenna element 10 (first conductor 11) is arranged so as to be electrically floating from the pylon 6. In other words, the antenna element 10 is arranged without being short-circuited to the pylon 6 so as to be able to generate a potential difference between the antenna element 10 and the pylon 6. In the example shown in Fig. 1, the antenna element 10 extending from the sensing device 100 is schematically illustrated.

[0051] In this way, in the sensing device 100, an antenna that receives electric field energy from the power transmission line 2 is configured using the antenna element 10 and the steel tower 6. This makes it possible to continuously harvest sufficient power as long as power is supplied to the power transmission line 2. As a result, it becomes possible to stably detect the state of high-voltage line-related equipment and the surrounding environment.

[0052] [Configuration of Sensing Device] Fig. 3 is a block diagram showing an example configuration of a sensing device. As described above, the sensing device 100 is configured to harvest the electric field energy of the AC electric field 60 as power. As shown in Fig. 3, the sensing device 100 has the antenna element 10, an antenna unit 15, a power generation unit 16, and a sensing unit 17.

[0053] The antenna element 10 is an antenna element included in the sensing device 100. The antenna element 10 is an example of the first conductor 11 described with reference to Fig. 2 , and is arranged so as not to be electrically connected to the steel tower 6, which is the second conductor 12.

[0054] A rod antenna or a cable antenna is used as the antenna element 10. A rod antenna is, for example, a rod-shaped antenna with a feed point at one end. The rod antenna may be attached to the housing of the sensing device 100, or may be fixed to a steel tower 6 or the like so as not to short-circuit. A cable antenna is, for example, a cable-shaped antenna with a feed point at one end. The cable antenna has, for example, an insulating resin coating or the like, and is appropriately arranged around the sensing device 100. The specific configuration of the antenna element 10 is not limited, and other antenna elements 10 such as a patch antenna may also be used.

[0055] The antenna length of the antenna element 10 is set so that the power output from the antenna unit 15 is equal to or less than a predetermined threshold. This is a configuration for deliberately suppressing the output of the antenna that receives electric field energy. The voltage of the power transmission line 2 is very high, for example, several hundred kilovolts, and it is conceivable that the power output from the antenna unit 15 will also be very large.

[0056] Therefore, for example, in order to protect downstream circuits such as the power generation unit 16, the antenna length of the antenna element 10 may be adjusted to limit the harvested power to a predetermined threshold or less. The predetermined threshold is set, for example, to a value equal to or less than the breakdown voltage of the diode (see FIG. 4) that constitutes the rectifier circuit 20 of the power generation unit 16. In addition, the antenna length, the arrangement of the antenna element 10, and the like may be set appropriately so as not to exceed the amount of power that can be harvested by the power generation unit 16.

[0057] The antenna unit 15 is connected to a first conductor 11 (the antenna element 10 in this example) and a second conductor 12 (the tower 6 in this example) that are provided near the power transmission line 2 (high-voltage line 1) and generate a potential difference between them, and an antenna is formed by the first conductor 11 and the second conductor 12. Specifically, the antenna unit 15 has a first connection portion 14a and a second connection portion 14b.

[0058] The first connection portion 14a connects the first conductor 11 and the rectifier circuit 20. For example, the wiring connecting the antenna element 10 to one input terminal 44a of the rectifier circuit 20 becomes the first connection portion 14a. The second connection portion 14b connects the second conductor 12 and the rectifier circuit 20. For example, the wiring connecting the pylon 6 to the other input terminal 44b of the rectifier circuit 20 becomes the second connection portion 14b. FIG. 1 schematically illustrates the wiring that becomes the first connection portion 14a and the second connection portion 14b. Note that the second connection portion 14b can be connected to the pylon 6 by, for example, screwing, crimping, welding, or the like.

[0059] The antenna section 15 is also provided with a protection circuit 18 for protecting the subsequent circuit from lightning surges, as will be described later with reference to Figs.

[0060] The power generation unit 16 harvests the output of the antenna unit 15 as electric power. In this embodiment, the antenna unit 15 mainly outputs AC received power corresponding to the AC electric field 60 of the power transmission line 2. The power generation unit 16 converts this AC received power into DC and harvests it. As shown in FIG. 3 , the power generation unit 16 has a rectifier circuit 20, a storage circuit 21, and a storage element 22.

[0061] The rectifier circuit 20 rectifies the output from the antenna unit 15. That is, the rectifier circuit 20 rectifies the AC received power induced between the first conductor 11 and the second conductor 12 by the AC power flowing through the power transmission line 2. This makes it possible to supply DC power to a downstream circuit, thereby enabling, for example, proper charging of the storage element 22. The storage circuit 21 is a circuit for charging the storage element 22 and controls the charging voltage and charging timing. The storage element 22 stores power harvested from the output of the antenna unit 15. In this embodiment, the storage circuit 21 charges the storage element 22 with the DC power output from the rectifier circuit 20. For example, a secondary battery is used as the storage element 22, but a capacitor or the like may also be used. The configurations of the rectifier circuit 20 and the storage circuit 21 will be described in detail later.

[0062] The sensing unit 17 is driven by power from the power generation unit 16, and performs a detection operation to detect the state of the related equipment 5 of the power transmission line 2 (high voltage line 1) or the surrounding environment using the status sensor 26. The detection operation performed by the sensing unit 17 includes various processes required to detect the state of the related equipment 5 or the surrounding environment, such as detection processing by the status sensor 26, transmission processing of the detection results, and adjustment processing of the status sensor 26.

[0063] The sensing unit 17 is a sensor unit of the sensing device 100 that performs such detection operations using power supplied from the power generation unit 16. In this embodiment, the sensing unit 17 is driven by power from a power storage element. By using the power storage element 22, it becomes possible to stabilize the supply of power to the sensing unit 17 and easily control the amount and timing of the supply. Furthermore, even if power transmission on the power transmission line 2 is stopped for some reason, it becomes possible for the sensing unit 17 to continue operating for a certain period of time.

[0064] As shown in FIG. 3, the sensing unit 17 includes a control unit 23, a communication unit 24, a storage unit 25, and a status sensor 26.

[0065] The control unit 23 is, for example, a computing device that controls the overall operation of the sensing device 100. The control unit 23 has hardware components necessary for a computer, such as a CPU and memory (RAM, ROM). The control unit 23 may be implemented using a programmable logic device (PLD) such as a field programmable gate array (FPGA), or other devices such as an application specific integrated circuit (ASIC). Alternatively, the control unit 23 may be implemented using any other logic circuit.

[0066] In the sensing device 100, the control unit 23 controls the detection operation for detecting the state of the related equipment 5 or the surrounding environment. For example, the timing of the detection process by the state sensor 26, the sensor parameters, etc. are set by the control unit 23. The detection result of the state sensor 26 is transmitted from the communication unit 24 via the control unit 23. In addition, any control required for the detection operation is performed.

[0067] The communication unit 24 is a module that communicates with external devices. The communication unit 24 performs communication related to detection operations. Communication related to detection operations includes, for example, a process of transmitting the detection results of the status sensor 26 to the management device 110, and a process of receiving instructions input from the management device 110. Data transmitted and received by the communication unit 24 is managed by the control unit 23.

[0068] The communication unit 24 is configured as a wireless communication module that performs wireless communication using, for example, a predetermined method. This allows the communication unit 24 to be connected to a network via a wireless communication base station or the like. For example, a technology called LPWA (Low Power Wide Area) can be used for wireless communication. LPWA is a wireless communication technology characterized by low power consumption and wide-area, long-distance communication. Among LPWA technologies, Wi-Fi halo, for example, is capable of relatively high-speed communication while consuming low power, enabling transmission of, for example, still images. Furthermore, the maximum transmission distance is expected to be approximately 10 km, allowing sufficient connection to a network even when the sensing device 100 is installed in a mountainous region. Alternatively, a method such as LTE-M using the LTE band may be used. The communication method of the communication unit 24 is not limited to this and may be selected appropriately depending on the intended use of the sensing device 100, etc.

[0069] The storage unit 25 is a non-volatile storage device, such as an SSD or HDD. A control program for operating the control unit 23 is stored in the storage unit 25. The detection results of the status sensor 26 may also be stored in the storage unit 25. This allows the sensing device 100 to function as a data logger. For example, when the communication situation is restored, processing may be performed such that the data that has been recorded up to that point is transmitted.

[0070] The status sensor 26 is a sensor for detecting the status of the related equipment 5 of the power transmission line 2 or the surrounding environment. In this embodiment, a camera sensor is used to photograph the power transmission line 2 and the steel tower 6. This makes it possible to easily and reliably check the status of the power transmission line 2 and the steel tower 6. Alternatively, for example, an inclination sensor that detects the inclination of the steel tower 6 may be used. In addition, the type of the status sensor 26 is not limited, and any sensor such as a vibration sensor, a wind sensor, a temperature sensor, or a rainfall sensor may be used.

[0071] [Configuration of Rectifier Circuit] FIG. 4 is a circuit diagram showing an example of the configuration of a rectifier circuit. As shown in FIG. 4, the rectifier circuit 20 is configured as a full-wave rectifier circuit. The rectifier circuit 20 includes four diodes 41a to 41d, two electrostatic protection components 42a, a Zener diode 42b, a backflow prevention diode 43, and output terminals 45a and 45b. The diodes 41a and 41b are connected in series in the forward direction, with the diode 41a at the head. An input terminal 44a is connected between the diodes 41a and 41b. The diodes 41c and 41d are connected in series in the forward direction, with the diode 41c at the head. An input terminal 44b is connected between the diodes 41c and 41d. The cathodes of the diodes 41a, 41c, and the Zener diode 42b, and one terminal of the electrostatic protection component 42a, are connected to the anode of the backflow prevention diode 43. The cathode of the reverse current prevention diode 43 is connected to the output terminal 45a. The anodes of the diodes 41b, 41d, and Zener diode 42b, and the other terminal of the electrostatic protection component 42a are connected to the output terminal 45b.

[0072] The first connection 14a connected to the antenna element 10 (first conductor 11) is connected to the input terminal 44a. The second connection 14b connected to the pylon 6 (second conductor 12) is connected to the input terminal 44b. For example, electric field energy received by the antenna formed by the antenna element 10 and the pylon 6 is supplied to the input terminals 44a and 44b as AC received power. The AC received power is full-wave rectified by four diodes 41a to 41d and output as DC power from the output terminals 45a and 45b. In this way, the rectifier circuit 20 shown in FIG. 4 is configured using the minimum number of diodes 41a to 41d required for full-wave rectification. This suppresses unnecessary leakage current and significantly improves the efficiency of capturing electric field energy.

[0073] The electrostatic protection component 42a is an element for dissipating static electricity and other electrical charges applied to the input terminals 44a and 44b. For example, when a high voltage such as static electricity occurs, the electrostatic protection component 42a functions to dissipate static electricity. For example, a varistor or the like can be used as the electrostatic protection component 42a. The Zener diode 42b is an element for protecting a downstream IC circuit (such as the power generation unit 16) connected to the output terminals 45a and 45b. For example, if the voltage between the input terminals 44a and 44b becomes 6.5 V or higher, the Zener diode 42b functions as a low-resistance conductor. This prevents damage to downstream circuits. The reverse current prevention diode 43 is a diode for preventing reverse current flow. By providing the reverse current prevention diode 43, reverse current flow can be suppressed, enabling stable operation of downstream circuits.

[0074] The configuration of the rectifier circuit 20 is not limited. For example, a voltage doubler rectifier circuit or a quadruple voltage rectifier circuit that uses a capacitor to multiply the voltage, or a rectifier circuit incorporating a Cockcroft-Walton circuit may be used. Alternatively, a half-wave rectifier circuit may be used. Alternatively, the rectifier circuit 20 may be configured as appropriate depending on the power reception characteristics of the antenna, the characteristics of the storage circuit, and the like.

[0075] The characteristics of rectifier diodes 41a to 41d will now be described. FIG. 5 is a table showing the forward voltage Vf and reverse current Is of the rectifier diodes. FIG. 6 is a graph of I-V measurements of the rectifier diodes shown in FIG. 5. Silicon and germanium rectifier diodes with part number 1N60 were measured, and evaluation was performed using the other part number ISS108. In FIG. 6, curve (a) shows the characteristics of 1N60 (silicon), curve (b) shows the characteristics of 1N60 (germanium), and curve (c) shows the characteristics of ISS108.

[0076] The reverse current Is is the current that flows when a voltage is applied in the reverse direction of a diode. The measurement data in Figure 5 is data when 10 V is applied in the reverse direction of the diode. The forward voltage Vf is the voltage at which a forward current (1 mA) begins to flow through the diode.

[0077] When the output of the antenna unit 15 is rectified, it was found that a 1N60 (silicon) diode, which does not allow reverse current to flow, can capture more power than a diode with a lower forward current flow voltage. Because the input to be rectified is AC, the reverse current Is when the diode's forward voltage Vf is applied in the reverse direction was evaluated. Considering that the reverse current Is shown in Figure 5 is 10 V, the reverse current Is when a voltage equal to Vf is applied in the reverse direction is calculated to be 0.036 μA for the 1N60 (silicon), 0.21 μA for the 1N60 (germanium), and 0.5 μA for the ISS108. Therefore, the ratio of the reverse current Is at a forward voltage Vf to the forward current (1 mA) is calculated to be 1 / 27778 for the 1N60 (silicon), 1 / 4762 for the 1N60 (germanium), and 1 / 2000 for the ISS108. In other words, the rectifying diodes (41a to 41d) used in the rectifying circuit 20 must have the above-mentioned ratio greater than approximately 4,700, and preferably the ratio is greater than or equal to 10,000. As a result, of the three diodes given as examples, 1N60 (silicon) has the most suitable characteristics.

[0078] Furthermore, considering the characteristics of the diode, the smaller the reverse current Is when applied in the reverse direction, the better. Using data from 10V, the reverse resistance values ​​calculated are 100 MΩ for 1N60 (silicon), 1.43 MΩ for 1N60 (germanium), and 0.38 MΩ for ISS108. In other words, a high resistance value that blocks reverse current flow is preferable. The rectifier diodes (41a to 41d) used in rectifier circuit 20 must have the above-mentioned resistance value greater than 1.43 MΩ, and preferably 10 MΩ or greater. As a result, of the three example diodes, 1N60 (silicon) has the most suitable characteristics.

[0079] FIG. 7 is a schematic circuit diagram showing an example configuration of a power storage circuit. The power storage circuit 21 includes a capacitor (capacitor element) 47 that stores the energy of the potential difference generated between the output terminals 45a and 45b of the rectifier circuit 20, a protective diode 48 connected downstream of the capacitor 47, and a charge / discharge control IC circuit 49. The charge / discharge control IC circuit 49 is connected to the power storage element 22, which is a secondary battery. The capacitor 47 smoothes the output of the rectifier circuit 20. The protective diode (Zener diode) 48 protects the charge / discharge control IC circuit 49. The charge / discharge control IC circuit 49 is an IC that controls the charging and discharging of the power storage element 22. A sensing unit 17, which serves as a load for the power storage element 22, is connected to the charge / discharge control IC circuit 49. The charge / discharge control IC circuit 49 is appropriately selected from step-down and step-up configurations depending on the harvested power, and controls the charging and discharging of the power storage element 22. For example, the power storage element 22 is charged using constant voltage charging. In addition, a protection function for the storage element 22, including prevention of overcharging, may be implemented. In addition, the configuration of the storage circuit 21 is not limited.

[0080] 1 and 3 , in this embodiment, the steel tower 6 is used as an antenna element. Therefore, for example, if lightning strikes the steel tower 6, it is conceivable that a high-voltage lightning surge will flow into the sensing device 100 via the antenna unit 15. In this case, for example, excessive current will flow through the circuits that make up the power generation unit 16 (rectifier circuit 20, storage circuit 21, storage element 22) in the sensing device 100, which may cause damage to the elements or a fire.

[0081] In order to avoid damage to the elements due to lightning surges, the antenna unit 15 is provided with a protection circuit that is placed between the antenna formed by the first conductor 11 (antenna element 10) and the second conductor (tower 6) and the power generation unit 16 to protect the power generation unit 16 from lightning surges.

[0082] Fig. 8 is a circuit diagram showing an example of a protection circuit against a lightning surge. The protection circuit 18a shown in Fig. 8 is configured using a transformer 30. The transformer 30 has a primary coil 32 connected to primary terminals 31a and 31b, and a secondary coil 34 connected to secondary terminals 33a and 33b.

[0083] The primary side terminal 31a is connected to the antenna element 10, and the primary side terminal 31b is connected to the pylon 6. The secondary side terminal 33a is connected to the input terminal 44a of the rectifier circuit 20, and the secondary side terminal 33b is connected to the input terminal 44b of the rectifier circuit 20. In this case, the wiring connecting the antenna element 10 and the primary side terminal 31a and the wiring connecting the secondary side terminal 33a and the input terminal 44a correspond to the first connection part 14a. Similarly, the wiring connecting the pylon 6 and the primary side terminal 31b and the wiring connecting the secondary side terminal 33b and the input terminal 44b correspond to the second connection part 14b.

[0084] The AC power input to the primary coil 32 is output from the secondary coil 34. As a result, the AC received power output from the antenna formed by the antenna element 10 and the steel tower 6 is supplied to the rectifier circuit 20 via the transformer 30.

[0085] On the other hand, the primary coil 32 and the secondary coil 34 are electrically separated. Therefore, even if lightning strikes the steel tower 6, for example, a lightning surge flowing from the steel tower 6 to the primary terminal 31b passes through the primary coil 32 and escapes to the antenna element 10 connected to the primary terminal 31a, and does not enter the rectifier circuit 20. This makes it possible to protect the power generation unit 16, including the rectifier circuit 20, from a lightning surge. When the transformer 30 is used, the device can be used continuously even after a lightning surge as long as the circuit is not damaged.

[0086] FIG. 9 is a circuit diagram showing another example of a protection circuit against lightning surges. The protection circuit 18b shown in FIG. 9 is configured using a fuse 36. The fuse 36 is an element that breaks when a current above a certain level flows. As shown in FIG. 9, in the antenna unit 15, the fuse 36 is provided in both the wiring (first connection portion 14a) connecting the antenna element 10 and the input terminal 44a of the rectifier circuit 20 and the wiring (second connection portion 14b) connecting the pylon 6 and the input terminal 44b of the rectifier circuit 20. Note that the fuse 36 may be provided only between the pylon 6 and the rectifier circuit 20.

[0087] For example, when the fuse 36 is not blown, the antenna element 10 and the tower 6 are each connected to the rectifier circuit 20 via the fuse 36. This allows AC received power to be supplied to the rectifier circuit 20. On the other hand, when lightning strikes the tower 6 and a lightning surge flows into the fuse 36 provided between the tower 6 and the rectifier circuit 20, the fuse 36 blows. This makes it possible to protect the power generation unit 16, including the rectifier circuit 20, from the lightning surge. The blown fuse 36 is replaced with a new fuse 36.

[0088] In this way, by providing the protection circuit 18a using the transformer 30 and the protection circuit 18b using the fuse 36, it is possible to prevent damage to elements, fire, etc. due to a lightning surge.

[0089] [Application Example of Sensing Device] Here, a specific example of the application of a sensing device arranged around the power transmission line 2 will be described. For example, the status sensor 26 may be configured to detect the status of power transmission facilities including the power transmission line 2 and the steel tower 6. An example of the status sensor 26 used for such an application is a camera sensor. The camera sensor is arranged so as to be able to photograph, for example, the power transmission line 2 and the steel tower 6. This makes it possible to monitor the status of the power transmission line 2 and the steel tower 6 with the camera sensor. This makes it possible to check, for example, damage or deterioration of the power transmission line 2 and the steel tower 6, the amount of snow accumulation, changes in status before and after an earthquake, etc. from a remote location at any time.

[0090] As the camera sensor, for example, a camera with a fixed magnification, a camera with a telephoto function, an infrared camera capable of nighttime photography, etc. may be used alone or in combination. A drive mechanism or the like for changing the shooting direction of the camera sensor may also be provided, and lighting equipment or the like for photography may also be provided. Furthermore, a tilt sensor (e.g., a three-axis acceleration sensor, etc.) for measuring the tilt of the steel tower 6 may also be used as the status sensor 26. The tilt sensor is installed, for example, on the legs of the steel tower 6. This makes it possible to quickly detect the tilt of the steel tower 6 due to earthquakes, deterioration over time, ground subsidence, etc.

[0091] The status sensor 26 may also be configured to detect the status of the environment surrounding the power transmission equipment. For example, if a camera sensor is used, it may be configured to capture images of the status of the surrounding environment, such as slopes and rivers, in addition to the power transmission equipment, such as the power transmission line 2 and the steel tower 6. This makes it possible to quickly detect slope collapses and rising river levels around the power transmission equipment. This information is important for conveying the local situation when, for example, planning maintenance and inspection. It also makes it possible to quickly check the status of natural disasters occurring around the power transmission line 2.

[0092] The sensing device 100 harvests electric field energy as power from the AC power flowing through the power transmission line 2. Therefore, if AC power is not flowing through the power transmission line 2, it is conceivable that the amount of power harvested will be significantly reduced. Utilizing this, it is possible to detect the presence or absence of power transmission.

[0093] Specifically, the sensing unit 17 (control unit 23) detects whether or not power is being transmitted through the power transmission line 2 (high-voltage line 1) based on the power harvesting state in the power generation unit 16, and transmits the detection result to an external device (such as the management device 110). For example, if the amount of power harvested decreases or if almost no power can be harvested, a message is transmitted indicating that power transmission has stopped in some or all of the power transmission lines.

[0094] Even if the power transmission is completely cut off, the sensing device 100 is equipped with a power storage element 22, allowing it to continue operating for a certain period of time. For example, by receiving information on the presence or absence of power transmission from multiple sensing devices 100, it becomes possible to easily identify locations in the power transmission network where power transmission has been interrupted. This makes it possible, for example, to quickly proceed with work to restore the power transmission network.

[0095] As described above, in the sensing device 100 according to this embodiment, the first conductor 11 (antenna element 10) and the second conductor 12 (steel tower 6), which are provided near the high-voltage power transmission line 1 (power transmission line 2) and have a potential difference between them, are used as an antenna, and the output of the antenna is harvested as power. This power is used to perform a detection operation in which a predetermined sensor detects the state of the equipment related to the high-voltage line 1 and the surrounding environment. This makes it possible to stably detect the state of the equipment related to the high-voltage line 1 and the surrounding environment.

[0096] Generally, power transmission facilities such as power lines and towers are inspected at regular intervals (for example, once a year). Such inspections require inspectors to actually visit the site, which is time-consuming and costly. Furthermore, since abnormalities cannot be detected until the inspection is carried out, there is a possibility that repairs will be delayed. From this perspective, there is a demand for a system that can remotely inspect power transmission facilities by installing sensor terminals at the inspection targets.

[0097] On the other hand, how to secure power for sensor terminals and other devices is an issue. For example, one possible method is to secure power using solar cells. However, solar cells are difficult to operate at night or in bad weather, making it difficult to operate sensor terminals stably.

[0098] In the sensing device 100 according to this embodiment, two conductors (a first conductor 11 and a second conductor 12) arranged near the high-voltage line 1 are used to form an antenna that harvests electric field energy from the high-voltage line 1 as power. This makes it possible to easily generate the DC power required to operate the sensing unit 17, which detects the state of the related equipment 5 and transmits the detection results.

[0099] Furthermore, because the sensing device 100 uses electric field energy from the high-voltage line 1, it is possible to harvest power stably regardless of weather or time. This allows the sensing system 120 to be operated stably. Furthermore, in the event of a sudden incident such as a natural disaster, it becomes possible to perform continuous monitoring without power outages and to quickly check the on-site condition, thereby significantly improving the reliability of the entire system.

[0100] Furthermore, the sensing device 100 can detect the presence or absence of power transmission through the high-voltage line 1 based on changes in the amount of harvested power. This makes it possible to quickly detect breaks in the power transmission line 2, including their locations. This makes it possible to quickly identify the location of a fault and quickly formulate repair plans for the power grid.

[0101] Second Embodiment A sensing device according to a second embodiment of the present technology will be described. In the following description, descriptions of parts having the same configurations and functions as those of the sensing device 100 described in the above embodiment will be omitted or simplified.

[0102] Fig. 10 is a schematic diagram showing an example configuration of a sensing device according to a second embodiment. As shown in Fig. 10 , in this embodiment, the high-voltage line 1 to which the sensing device 200 is applied is an electric train line 3 that supplies power to a train 7. The electric train line 3 is, for example, an overhead line for transmitting power that is stretched above a rail 8 on which the train 7 runs. The electric train line 3 is fixed to a support for the overhead power transmission line, such as a concrete pillar or a portal tower, via insulators or the like. The electric train line 3 is an example of the high-voltage line 1 in the present disclosure, and the train 7 to which power is supplied from the electric train line 3 and the rail 8 on which the train 7 runs are examples of related equipment 5 for the high-voltage line 1.

[0103] In this embodiment, a case will be mainly described in which AC power flows through the electric contact line 3 (high-voltage line 1). For example, in Japan, examples of the voltage of AC power used in the electric contact line 3 include single-phase 20 kV, single-phase 25 kV, and three-phase 600 V.

[0104] In this case, similarly to the above embodiment, the sensing device 200 is configured to be able to harvest, as power, the electric field energy of the AC electric field formed by the AC power flowing through the electric train line 3. Note that DC power may also be used for the electric train line 3. For the electric train line 3 to which DC power is supplied, the configurations shown in Figs. 17 to 19 can be applied.

[0105] In this embodiment, the antenna element 10 and the metal part 9 of the train 7 are used as conductors that constitute the antenna that receives electric field energy from the trolley line 3. Here, the antenna element 10 corresponds to the first conductor 11, and the metal part 9 of the train 7 corresponds to the second conductor 12.

[0106] In this way, since the metal part 9 of the train 7 is used as an antenna element, the sensing device 200 is mounted on the train 7. That is, the sensing device 200 detects the state of the train 7 while moving together with the train 7.

[0107] Fig. 11 is a block diagram showing an example of the configuration of the sensing device shown in Fig. 10. As shown in Fig. 11, the sensing device 200 has an antenna element 10 which is a first conductor 11, an antenna unit 15, a power generation unit 16, and a sensing unit 17. The metal part 9 of the train 7 is used as the second conductor 12 connected to the antenna unit 15. Note that the configurations described with reference to Fig. 3 can be used for the antenna unit 15, the power generation unit 16, and the sensing unit 17.

[0108] The metal parts 9 (second conductors 12) of the electric train 7 are, for example, structural members such as a metal frame that constitutes the electric train 7, or exterior members that constitute the body, etc. The structural members and exterior members of the electric train 7 are generally grounded to the earth ground 4 via the rails 8. Therefore, the metal parts 9 of the electric train 7 are ideally grounded to the earth ground 4, but in reality, they are grounded via structures such as the wheels of the electric train 7, so it is possible that they may be slightly floating above the earth ground 4.

[0109] 10 , the antenna unit 15 (second connection portion 14b) is electrically connected to an exterior member constituting the roof portion of the train 7, which is the metal portion 9 of the train 7. Of course, there are no limitations on the member or position to which the antenna unit 15 is connected as long as it is the metal portion 9 of the train 7. In this embodiment, the metal portion 9 of the train 7 is an example of a metal body constituting the related equipment 5 of the electric train line 3 (high-voltage line 1).

[0110] The antenna element 10 (first conductor 11) is provided on the train 7 so as to be electrically floating from the metal part 9 of the train 7. A rod antenna, a cable antenna, or the like can be used as the antenna element 10. In the example shown in FIG. 10 , the antenna element 10 is provided on the roof of the train 7 so as not to short-circuit with the metal part 9 of the train 7. In addition, the antenna part 15 (first connection part 14 a) is electrically connected to the feeding point of the antenna element 10.

[0111] In this way, by providing a metal (antenna element 10) above the train 7 that is floating above the train body, an antenna that receives electric field energy from the train line 3 is configured directly below the train line 3. This makes it possible to harvest the electric field energy from the train line 3 as power, and enables stable operation of the sensing system that moves along with the train 7.

[0112] In the sensing device 200 provided on the train 7, the running state of the train 7 is detected by a status sensor 26. For example, a vibration sensor, a noise sensor, or the like may be provided as the status sensor 26. This makes it possible to easily monitor the vibration and noise levels of the train while it is running. In addition, a temperature sensor that detects the temperature of each part of the train 7, or a sensor that detects the movement of the train 7, such as a position sensor, a speed sensor, or an acceleration sensor, may be used as the status sensor 26.

[0113] The status sensor 26 may also be configured to detect the status of the environment surrounding the train 7. For example, a camera sensor or the like may be used to appropriately photograph the status of related facilities around the tracks (railroad crossing facilities, signal facilities, power facilities, etc.). In addition, the status of the topography and structures around the tracks (slope, bridge piers, tunnels, etc.) may also be photographed. This makes it possible to monitor the status of various facilities and locations on the route of the train 7. Furthermore, the type and use of the status sensor 26 provided in the sensing device 200 are not limited.

[0114] <Third embodiment> Fig. 12 is a schematic diagram showing an example of the configuration of a sensing device according to a third embodiment. As shown in Fig. 12, in this embodiment, the high-voltage line 1 to which the sensing device 300 is applied is the electric train line 3 that supplies power to a train 7, as in the cases of Figs. 10 and 11. Furthermore, in this embodiment, a case will be mainly described in which AC power flows through the electric train line 3 (high-voltage line 1), but the configurations shown in Figs. 17 to 19 can also be applied to the electric train line 3 that supplies DC power.

[0115] In this embodiment, the antenna element 10 and the rail 8 on which the train runs are used as conductors that constitute the antenna that receives electric field energy from the electric train line 3. Here, the antenna element 10 corresponds to the first conductor 11, and the rail 8 corresponds to the second conductor 12.

[0116] Since the rail 8 serves as an antenna element, the sensing device 300 is placed near the rail 8. Therefore, unlike the sensing device 200 described with reference to Fig. 10 etc., the sensing device 300 is a stationary device.

[0117] Fig. 13 is a block diagram showing an example of the configuration of the sensing device shown in Fig. 12. As shown in Fig. 13, the sensing device 300 has an antenna element 10 which is a first conductor 11, an antenna unit 15, a power generation unit 16, and a sensing unit 17. A rail 8 is used as a second conductor 12 connected to the antenna unit 15. Note that in this embodiment, a configuration in which something other than the antenna element 10 is used as the first conductor 11 will also be described later.

[0118] The rail 8 (second conductor 12) is formed by arranging, for example, columnar metal members each having a predetermined length. Each metal member is grounded to the earth ground 4 by a predetermined metal anchor or the like. Therefore, the rail 8 is ideally grounded to the earth ground 4, but in reality, it is assumed that the rail 8 may be slightly floating above the earth ground 4 due to the presence of ground resistance and impedance components (resistance components to AC).

[0119] Fig. 14 is a schematic diagram showing an example of connection between the sensing device 300 and rails 8. Fig. 14 schematically shows two rails 8 (rail 8a and rail 8b) grounded to the earth ground 4 and the trolley line 3 arranged directly above them. Here, the antenna unit 15 (second connection portion 14b) is electrically connected to one of the two rails 8 (here, the lower rail 8b in the figure).

[0120] The antenna element 10 (first conductor 11) is provided near the rail 8b. A rod antenna, a cable antenna, or the like can be used as the antenna element 10. In the example shown in Fig. 14, the antenna element 10 is provided at a position several meters away from the rail 8b so as not to short-circuit with the rail 8b. An antenna section 15 (first connection section 14a) is electrically connected to the feeding point of the antenna element 10.

[0121] As a result, the antenna element 10 and the rail 8b form a stationary antenna that receives electric field energy from the electric train line 3. As a result, it becomes possible to harvest the electric field energy from the electric train line 3 as electric power, and it becomes possible to stably operate a sensing system that monitors the train 7, wayside facilities, etc.

[0122] Fig. 15 is a schematic diagram showing another example of connection between a sensing device and a rail. In the sensing device 301 shown in Fig. 15, an earth member 65 connected to earth ground is used as the antenna element 10, which is the first conductor 11. The earth member 65 is, for example, a metal anchor driven into the ground. Note that the rail 8b is used as the second conductor 12, as in Fig. 14.

[0123] Therefore, in the sensing device 301, both the first conductor 11 (earth member 65) and the second conductor 12 (rail 8b) are grounded to the earth ground 4. In this case, ideally, the first conductor 11 and the second conductor 12 should be at the same potential, and no potential difference should occur. However, as described above, the rail 8 functions as a metal body that is slightly floating above the earth ground 4, and an AC current is induced in the rail 8b, for example, by the AC electric field 60 formed by the contact line 3. As a result, AC received power is also generated between the earth member 65 and the rail 8b, making it possible to harvest the electric field energy as power.

[0124] Fig. 16 is a schematic diagram showing another example of connection between a sensing device and a rail. In the sensing device 302 shown in Fig. 16, a rail 8 other than the rail 8 serving as the second conductor 12 is used as the first conductor 11. Here, the rail 8b on the lower side in the figure is used as the conductor (second conductor 12) connected to the second connection portion 14b. In this case, the rail 8a on the upper side in the figure is used as the conductor (first conductor 11) connected to the first connection portion 14a. This is an example of a configuration in which the first conductor 11 and the second conductor 12 are both metal bodies that constitute related equipment for the high-voltage line 1.

[0125] As described above, in the sensing device 302, the first conductor 11 and the second conductor 12 are both rails 8 grounded to the earth ground 4. In this case, ideally, the rails 8a and 8b would be at the same potential, but in reality, due to ground resistance, impedance components, etc., the rails 8a and 8b become metal bodies that are slightly floating above the earth ground 4. For this reason, AC currents are induced individually in the rails 8a and 8b by the AC electric field 60 formed by the contact line 3. As a result, AC received power is also generated between the rails 8a and 8b, making it possible to harvest the electric field energy as power.

[0126] In this way, by utilizing the rails 8 on which the train 7 runs, an antenna is configured to receive electric field energy from the contact line 3. This makes it possible to harvest the electric field energy from the contact line 3 as power, and enables the sensing system to operate stably around the rails 8.

[0127] In the sensing devices 300, 301, and 302 installed around the rails 8, the status of the wayside facilities, including the rails 8, is detected by the status sensor 26. The wayside facilities include not only the rails 8 but also various facilities attached to the tracks, such as signaling facilities, communication facilities, railroad crossing facilities, power transmission facilities, and snow melting facilities. These facilities require periodic inspections to maintain their proper functionality. For example, the current, voltage, and other conditions of each facility must be checked every three or six months. Therefore, by providing an ammeter or voltmeter as the status sensor 26, it is possible to build a remote monitoring system that monitors the status of such facilities. Furthermore, if a camera sensor or the like is used as the status sensor 26, it is possible to visually monitor the status of each facility. Furthermore, a temperature sensor can be provided to measure the temperature, etc., of the wayside facilities.

[0128] Furthermore, the status sensor 26 may be configured to detect the status of the environment surrounding the wayside facilities. For example, a camera sensor or the like may be used to capture images of the topography and the status of structures around the tracks. By using the sensing devices 300, 301, 302, it is possible to build a monitoring system that constantly monitors any location, for example, and to quickly check changes in the surrounding environment due to typhoons, earthquakes, etc. Furthermore, it may be configured to measure information on the passing of the train 7, and the vibration and noise levels when the train 7 passes. There are no limitations on the type or use of the status sensor 26 provided in the sensing devices 300, 301, 302.

[0129] 17 is a block diagram showing an example of the configuration of a sensing device according to a fourth embodiment. In the above embodiments, the high-voltage line 1 has mainly been described as transmitting AC power. In this embodiment, the high-voltage line 1 transmits DC power. Therefore, a sensing device 400 that harvests power from the high-voltage line 1 is configured to be able to harvest the electric field energy of the electrostatic field formed by the DC power flowing through the high-voltage line 1 as power.

[0130] 17, the sensing device 400 has an antenna element 10, an antenna unit 15, a power generation unit 66, and a sensing unit 17. Of these, the configuration of the power generation unit 66, which is the configuration for harvesting the electric field energy of the electrostatic field as power, is mainly different from the above embodiment.

[0131] First, a method for harvesting the electric field energy of an electrostatic field as electric power will be described. Fig. 18 is a schematic diagram illustrating energy harvesting using a high-voltage line that transmits DC power. Fig. 18 schematically illustrates a high-voltage line 1 that transmits DC power and two conductors (a first conductor 11 and a second conductor 12) that serve as antennas that receive the electric field energy from the high-voltage line 1.

[0132] The first conductor 11 and the second conductor 12 are provided near the high-voltage line 1 and generate a potential difference between them. Here, the first conductor 11 is a conductor floating above the earth ground 4, and the second conductor 12 is a conductor grounded to the earth ground 4. Note that the second conductor 12 does not necessarily have to be grounded to the earth ground 4 as long as it is not short-circuited with the first conductor 11.

[0133] As shown in Figure 18, in this embodiment, positive DC power is passed through the high-voltage line 1. In this case, the high-voltage line 1 is positively charged, and an electrostatic field 62 is formed around the high-voltage line 1. Furthermore, charges corresponding to the electrostatic field 62 are induced by electrostatic induction in the first conductor 11 and the second conductor 12, which are capacitively coupled to the high-voltage line 1. Note that the capacitive coupling between the first conductor 11 and the high-voltage line 1 and the capacitive coupling between the second conductor 12 and the high-voltage line 1 are separate couplings. Therefore, the charge distributions induced in the first conductor 11 and the second conductor 12 are different from each other. Due to this imbalance of charge in each conductor, a potential difference occurs between the first conductor 11 and the second conductor 12. Furthermore, the potential difference between the first conductor 11 and the second conductor 12 generates DC power corresponding to the potential difference, functioning as a DC power supply 63.

[0134] In this way, the first conductor 11 and the second conductor 12 form an antenna that receives the electric field energy of the electrostatic field 62. Furthermore, if the DC power of the high-voltage line 1 is constant, the potential difference between the two antenna elements is maintained. In other words, the antenna formed by the first conductor 11 and the second conductor 12 functions as a DC power supply 63 that outputs received DC power when the high-voltage line 1 transmits DC power. The sensing device 400 utilizes this characteristic to harvest the electric field energy of the electrostatic field 62 as power.

[0135] In this embodiment, an example will be described in which an electric train line 3 that supplies power to a train 7 is used as the high-voltage line 1 for transmitting DC power. For example, in Japan, examples of the voltage of DC power used for the electric train line 3 include 15 kV, 750 V, and 600 V.

[0136] 17, in the sensing device 400, an antenna element 10 and a rail 8 on which a train runs are used as conductors that constitute an antenna that receives electric field energy from the trolley line 3. Here, the antenna element 10 corresponds to a first conductor 11, and the rail 8 corresponds to a second conductor 12. This configuration is similar to that of the sensing device 300 described with reference to, for example, Figures 12 to 14. Of course, it is also possible to use the connection examples described with reference to, for example, Figures 10, 15, and 16.

[0137] Next, we will explain the configuration of the power generation unit 66. The power generation unit 66 has a power storage circuit 67 and a power storage element 22. The power storage circuit 67 is a circuit that stores DC received power that flows due to a potential difference induced between the first conductor 11 (the antenna element 10 in this case) and the second conductor 12 (the rail 8 in this case) by the DC power of the high-voltage line 1.

[0138] 19 is a schematic circuit diagram showing an example of the configuration of a power storage circuit 67. The power storage circuit 67 has a capacitor (capacitive element) 51 that stores the energy of the potential difference generated between the output terminals 50a and 50b of the antenna unit 15, a protective diode 52 connected downstream of the capacitor 51, and a charge / discharge control IC circuit 53. A power storage element 22, which is a secondary battery, is connected downstream of the charge / discharge control IC circuit 53.

[0139] This configuration is the same as the sensing device 100 described with reference to Fig. 7, except that the rectifier circuit 20 is removed. In this way, when the power flowing through the high-voltage line 1 is DC power, the power received by the antenna is also DC, so there is no need to provide a rectifier circuit. This simplifies the circuit configuration and reduces device costs.

[0140] Fifth Embodiment Fig. 20 is a block diagram showing an example of the configuration of a sensing device according to a fifth embodiment. In a sensing device 500 according to this embodiment, a transformer 70 for impedance matching is provided between the antenna unit 15 and the rectifier circuit 20. First, the configuration of the sensing device 500 will be described. As shown in Fig. 20, the sensing device 500 has the antenna unit 15, the transformer 70, a power generation unit 16, and a sensing unit 17.

[0141] The antenna unit 15 is a receiving antenna that receives electromagnetic noise generated from the high-voltage line 1 as a noise source N. The antenna unit 15 is connected to a first conductor 11 and a second conductor 12 that are provided near the high-voltage line 1 and generate a potential difference between them, forming an electric field antenna. Here, the first conductor 11 and the second conductor 12 are collectively referred to as the antenna unit 15.

[0142] Specifically, the antenna unit 15 has a first conductor 11, a second conductor 12, a first connection portion 14a, and a second connection portion 14b. The first connection portion 14a is a wiring for connection to the first conductor 11, and the second connection portion 14b is a wiring for connection to the second conductor 12. The first connection portion 14a and the second connection portion 14b are each connected to a transformer 70. The connection between the first connection portion 14a and the second connection portion 14b and the transformer 70 will be described later with reference to FIG. 21 .

[0143] 2, the first conductor 11 and the second conductor 12 are conductors that are not electrically connected to the high-voltage line 1 (noise source N), i.e., conductors that are floating from the high-voltage line 1. Metal bodies are typically used as the first conductor 11 and the second conductor 12.

[0144] Electromagnetic noise induces electric field energy of various frequencies in the first conductor 11 and the second conductor 12 provided near the high-voltage line 1. This allows the antenna unit 15 to receive electric field energy in a wide frequency band. For example, the frequency components of the electromagnetic noise received by the antenna unit 15 include components of a radiated electromagnetic field (so-called radio waves) propagating through space.

[0145] Furthermore, the frequency components of the electromagnetic noise received by the antenna unit 15 include quasi-electrostatic field components of the electromagnetic waves radiated from the high-voltage line 1 and induced electromagnetic field components induced by the current flowing through the high-voltage line 1. Here, the quasi-electrostatic field does not have the propagating property of a radiated electromagnetic field, but refers to a voltage phenomenon that is distributed, for example, like electrostatic charge, near the high-voltage line 1 or surrounding materials. While a static field is considered to have zero time change, the quasi-electrostatic field has frequency components and is subject to time change. The induced electromagnetic field components are components that are generated in the first conductor 11 and the second conductor 12 by electromagnetic induction when a current flows through the high-voltage line 1. The quasi-electrostatic field components and induced electromagnetic field components are lower frequency components than, for example, the frequency components of a radiated electromagnetic field, and are mainly conductive noise.

[0146] The transformer 70 is connected between the antenna unit 15 and the rectifier circuit 20. The antenna unit 15 is connected to the primary side, which is the input side of the transformer 70, and the rectifier circuit 20 is connected to the secondary side, which is the output side of the transformer 70. The AC power output from the antenna unit 15 is transformed by the transformer 70 and output to the rectifier circuit 20.

[0147] The power generation unit 16 is a circuit that harvests AC power output from the antenna unit 15. The power generation unit 16 is configured, for example, similarly to that shown in Fig. 3 and includes a rectifier circuit 20, a power storage circuit 21, and a power storage element 22. Of these, the power storage circuit 21 and the power storage element 22 provided in the subsequent stage of the rectifier circuit 20 serve as a load element 76.

[0148] The rectifier circuit 20 rectifies the AC power output from the antenna unit 15. Specifically, the rectifier circuit 20 rectifies the AC power output from the antenna unit 15 via the transformer 70, and outputs the rectified AC power as DC power to a load element 76 provided downstream. In this way, the sensing device 500 supplies the output from the rectifier circuit 20 to the load element 76.

[0149] The load element 76 is an element that serves as a load in the power generation unit 16. Here, the storage circuit 21 and the storage element 22 serve as the load element 76. When the sensing unit 17 is driven without using the storage element 22, the sensing unit 17 connected to the power generation unit 16 serves as the load element 76. The configuration of the load element 76 is not limited to this.

[0150] In the sensing device 500, the power generation unit 16 including the load element 76 can be regarded as a load for the antenna unit 15. That is, the sensing device 500 has a configuration in which the antenna unit 15 and the load are connected via the transformer 70.

[0151] In this case, by appropriately setting the characteristics (winding ratio, resistance ratio, etc.) of the transformer 70, it is possible to achieve impedance matching between the circuit connected to the primary side (antenna unit 15) and the circuit connected to the secondary side (power generation unit 16 including load element 76). Here, impedance matching means, for example, bringing the impedance of the circuit connected to the primary side of the transformer 70 closer to the impedance of the circuit connected to the secondary side so that power can be harvested at a desired level, and the two do not necessarily need to match.

[0152] In the present disclosure, the transformer 70 is configured to achieve impedance matching between the antenna unit 15 and the power generation unit 16 including the load element 76 in a target frequency band described below. That is, the transformer 70 brings the impedance of the antenna unit 15 in the target frequency band closer to the impedance of the power generation unit 16 (the rectifier circuit 20 and the load element 76) in the target frequency band. This point will be described in detail later.

[0153] 21 is a circuit diagram showing an example of the configuration of the sensing device 500. The circuit configuration of each part of the sensing device 500 will be described below with reference to FIG.

[0154] As described above, the antenna unit 15 has the first connection portion 14a and the second connection portion 14b. The first connection portion 14a is, for example, a wiring that connects the first conductor 11 and one terminal on the primary side of the transformer 70 (primary-side connection end 71a). The second connection portion 14b is, for example, a wiring that connects the second conductor 12 and the other terminal on the primary side of the transformer 70 (primary-side connection end 71b).

[0155] If the input of the transformer 70 is reversible, the first connecting portion 14a and the second connecting portion 14b may be connected to the transformer 70 in the opposite manner to that described above. That is, the second connecting portion 14b (second conductor 12) may be connected to the primary side connecting end 71a, and the first connecting portion 14a (first conductor 11) may be connected to the primary side connecting end 71b.

[0156] The transformer 70 has primary connection terminals 71 a and 71 b, a primary coil 72, secondary connection terminals 73 a and 73 b, and a secondary coil 74. The primary coil 72 is connected between the primary connection terminals 71 a and 71 b. The secondary coil 74 is connected between the secondary connection terminals 73 a and 73 b. Here, the side where the primary coil 72 is connected to the primary connection terminal 71 a and the side where the secondary coil 74 is connected to the secondary connection terminal 73 a are indicated by black circles.

[0157] The transformer 70 is a single-phase winding transformer in which the primary coil 72 and the secondary coil 74 are configured as single-phase coils. Typically, a core transformer in which the primary coil 72 and the secondary coil 74 are wound around a core such as an iron core is used, but an air-core transformer or the like may also be used. The type of the transformer 70 is not limited to this.

[0158] 21 also shows a circuit diagram of the rectifier circuit 20 of the power generation unit 16. The rectifier circuit 20 is configured, for example, in the same manner as in FIG. 4. A load element 76 (the power storage circuit 21 and the power storage element 22) is connected between the output terminals 45a and 45b of the rectifier circuit 20. Note that the load element 76 is shown here as a single element.

[0159] [Characteristics of AC Power Output from Antenna Unit] Below, the characteristics of AC power output from the antenna unit 15 will be described using an example of a device that harvests power from a noise source N included in a relatively small electrical device. Here, a case where the antenna unit 15 is configured near the noise source N of the electrical device will be described, but the same explanation applies when the antenna unit 15 is configured near the high-voltage line 1 (noise source N).

[0160] Fig. 22 is a circuit diagram showing a power harvesting device as a comparative example. In the comparative power harvesting device 510 shown in Fig. 22, the transformer 70 is not provided, and the antenna unit 15 and the rectifier circuit 20 are directly connected. That is, the first connection part 14a is connected to the input terminal 44a of the rectifier circuit 20, and the second connection part 14b is connected to the input terminal 44b of the rectifier circuit 20.

[0161] Here, the frequency characteristics of AC power (electromagnetic noise) output from the antenna unit 15 were measured using a fluorescent lamp 28a as an example of electrical equipment 28. In this measurement, the first connection 14a was connected to the metal part 29 (first conductor 11) of the fluorescent lamp 28a, and the second connection 14b was connected to the earth part 27 (second conductor 12) connected to the earth ground 4. Furthermore, no load element 76 was connected to the power generation unit 16, and the output terminals 45a and 45b were left open. In this state, a real-time oscilloscope was connected to the first connection 14a as a measurement point (white circle in the figure), and the noise level (AC power output from the antenna unit 15) was measured.

[0162] Fig. 23 is a graph showing the frequency spectrum of fluorescent light noise. The horizontal axis of the graph represents frequency [kHz], and the vertical axis represents the noise power level [dBm]. As shown in Fig. 23, the noise from fluorescent light 28a has a peak at 49 kHz. Furthermore, on the higher frequency side, a peak of the 49 kHz harmonic component was observed. The output of antenna unit 15 connected to fluorescent light 28a includes these peaks.

[0163] In this way, the antenna unit 15 coupled to the noise source N of the electrical device 28 (here, fluorescent lamp 28a) outputs various frequency components. Hereinafter, as shown in Fig. 22 , the circuit in which the noise source N of the electrical device 28 and the antenna unit 15 are coupled will be referred to as a noise power source 75. The noise power source 75 can be regarded as an AC power source that outputs electric field energy corresponding to the electromagnetic noise generated by the noise source N.

[0164] Next, the characteristics of the voltage generated across the load element 76 when the load element 76 is connected to the comparative power harvesting device 510 will be described. FIG. 24 is a circuit diagram showing an example of measuring the voltage generated across the load element 76. As shown in FIG. 24 , with the comparative power harvesting device 510 connected to the metal part 29 of the fluorescent lamp 28a, the load element 76 was connected to the rectifier circuit 20 (power generation unit 16), and the voltage generated across the load element 76 (between the output terminals 45a and 45b) was measured. The generated voltage is the output voltage of the comparative power harvesting device 510 generated for each load element 76.

[0165] Test resistors with resistance values ​​of 1 MΩ and 10 kΩ were used as the load element 76. Hereinafter, the voltage generated when the test resistor with the higher resistance value (1 MΩ in this case) was connected will be referred to as V1, and the voltage generated when the test resistor with the lower resistance value (10 kΩ in this case) was connected will be referred to as V2.

[0166] Here, consider a hypothetical model (noise power source model) of a noise power source 75 consisting of a noise source N and an antenna unit 15. The noise power source model can be considered as a circuit in which an internal resistor is connected to the noise source N that generates noise (see FIG. 33).

[0167] Figure 25 is a schematic diagram illustrating the characteristics of a noise power source model in which the internal resistance is a simple resistance. The graph on the left side of Figure 25 is a schematic graph plotting the generated voltage V1 obtained when a 1 MΩ test resistor is connected and the generated voltage V2 obtained when a 10 kΩ test resistor is connected at each frequency. These generated voltages V1 and V2 represent the noise level for each frequency. The graph on the right side of Figure 25 is a schematic graph plotting the voltage ratio (V2 / V1) based on 1 MΩ at each frequency.

[0168] As shown on the left side of Figure 25, the noise level varies depending on the value of the test resistor connected to the rectifier circuit 20. Generally, the higher the value of the test resistor, the higher the noise level obtained. Therefore, the noise level (generated voltage V1) when the test resistor is 1 MΩ is higher than the noise level (generated voltage V2) when the test resistor is 10 kΩ. The noise level also varies depending on the frequency. Considering the noise power source model, these noise levels are determined by the output level of the noise source N at each frequency and the resistance value of the internal resistor.

[0169] If the internal resistance of the noise power source 75 is assumed to be independent of frequency, a noise power source model can be considered in which the internal resistance is represented by a simple resistive element. In this case, the resistance value of the internal resistance of the noise power source 75 is constant with respect to frequency. Therefore, although the noise level (generated voltage V1 or generated voltage V2) at each frequency can take on various values, the voltage ratio (V2 / V1) is constant. Therefore, when the voltage ratio is plotted, a flat graph (a linear graph that does not change with frequency) is obtained, as shown on the right side of Figure 25.

[0170] Fig. 26 is a schematic diagram illustrating the characteristics of a noise power source model when the internal resistance has complex components. In the example shown on the left side of Fig. 26, the difference between generated voltage V1 and generated voltage V2 is large in the low-frequency region. When such a tendency is observed, the voltage ratio (V2 / V1) changes with frequency. This means that, in terms of the noise power source model, the internal resistance changes with frequency, i.e., the resistance value of the internal resistance has complex components. In other words, the internal resistance includes a capacitance component and an inductance component.

[0171] In the region where the internal resistance contains a complex component, it is expected that the voltage ratio (V2 / V1) increases nonlinearly as the frequency increases, as shown on the right side of Figure 26. Note that the influence of the complex component seen on the low frequency side decreases as the frequency increases. Therefore, as the frequency increases, the voltage ratio (V2 / V1) eventually converges to a certain level.

[0172] Hereinafter, the frequency region in which the voltage ratio (V2 / V1) converges to a constant level will be referred to as the linear region. The frequency region in which the voltage ratio (V2 / V1) fluctuates below the linear region will be referred to as the nonlinear region. In the nonlinear region, V2 / V1 increases nonlinearly with frequency. Therefore, the nonlinear region can also be said to be a region in which the amount of fluctuation of V2 / V1 with respect to frequency is greater than in the linear region.

[0173] In this noise power source model in which the internal resistance has a complex component, the lower the frequency range, the greater the rate of change when the resistance value of the load element 76 (test resistor) is changed. For example, in the nonlinear range, when a load element 76 with a low resistance value is connected, the generated voltage is significantly reduced compared to when the resistance value is high.

[0174] Here, let us consider Ohm's law (V = IR) where the resistance of the load element 76 is R, the voltage (generated voltage) applied to the load element 76 is V, and the current flowing through the load element 76 is I. In this case, the resistance R of the load element 76 does not change, so the voltage V applied to the load element 76 decreases, and the current I flowing through the load element 76 also decreases significantly. This means that the ability to pass current decreases significantly. As a result, it is conceivable that almost no current I will flow through the load element 76. In other words, in a noise power source 75 whose internal resistance has a complex component, it may be impossible for the current I to flow, depending on the frequency.

[0175] FIG. 27 is a graph showing the frequency characteristics of the voltage ratio when the resistance value of the load element 76 in FIG. 24 is changed. The horizontal axis of the graph represents frequency [kHz], and the vertical axis represents the voltage ratio (V2 / V1). As shown in FIG. 27, when connected to the metal part 29 of the fluorescent lamp 28a, V2 / V1 rises to approximately 200 kHz and then converges to a certain level (here, approximately 0.8). This result indicates that the internal resistance of the noise power source 75, including the noise source N of the fluorescent lamp 28a, has a complex component. Therefore, it is considered that the noise level of the fluorescent lamp 28a is in a nonlinear region below 200 kHz and in a linear region above 200 kHz.

[0176] Next, we will explain the measurement of noise levels using a copier as the electrical device 28. FIG. 28 is a circuit diagram showing another example of measuring the voltage generated across the load element 76. In the measurement shown in FIG. 28, the first connection portion 14a was connected to the metal portion 29 (first conductor 11) of the copier 28b, and the second connection portion 14b was connected to the earth portion 27 (second conductor 12). The load element 76 was also connected to the rectifier circuit 20 (power generating portion 16), and the voltage generated across both ends of the load element 76 (between the output terminals 45a and 45b) was measured. Test resistors with resistances of 1 MΩ and 30 kΩ were used as the load element 76.

[0177] 29 is a graph showing the frequency characteristics of the generated voltage when the resistance value of the load element 76 in FIG. 28 is changed. The horizontal axis of the graph is frequency [Hz], and the vertical axis is generated voltage [V]. Here, generated voltage V1 when a test resistor of 1 MΩ is connected and generated voltage V2 when a test resistor of 30 kΩ is connected are plotted.

[0178] 29, for example, at 50 Hz, when a 1 MΩ test resistor is connected, the generated voltage V1 is about 60 V, which is a high voltage. In contrast, when a 30 kΩ test resistor is connected, the generated voltage V2 is about 5 V, which is a significant drop in the generated voltage. In other words, it can be seen that the current flowing through the test resistor (load element 76) is significantly lower than when the resistance value is high.

[0179] This decreasing trend continues up to approximately 7 kHz, and at frequencies above that, there is no difference between the generated voltage V1 and the generated voltage V2. In other words, at frequencies above 7 kHz, the same voltage is output even if the resistance value of the test resistor (load element 76) changes. This means that the current flowing to maintain a constant voltage increases. Thus, with regard to the noise level of the copier 28b, for example, frequencies below 7 kHz are considered to be in a nonlinear region, and frequencies above 7 kHz are considered to be in a linear region.

[0180] 30 is a circuit diagram showing an example of measuring the voltage generated in a load element 76 connected to a noise power source 75. In FIG. 30, the load element 76 is directly connected between the metal part 29 (first conductor 11) and the earth part 27 (second conductor 12) of a stabilized power supply 28c, which is an electrical device 28. In this case, the wiring connecting the metal part 29 and the load element 76 corresponds to the first connection part 14a of the antenna part 15. The wiring connecting the earth part 27 and the load element 76 corresponds to the second connection part 14b of the antenna part 15. This allows the voltage generated at the output end of the noise power source 75 to be directly measured.

[0181] In the measurement, the voltage V' generated across the load element 76 was detected using an oscilloscope. Test resistors with resistance values ​​of 1 MΩ, 100 kΩ, and 10 kΩ were used as the load element 76. The voltage was also measured in an open state with the load element 76 not connected. This voltage corresponds to the open voltage of the antenna unit 15.

[0182] 31 is a graph showing the waveform of the generated voltage when the resistance value of the load element 76 in FIG. 30 is changed. The horizontal axis of the graph represents time [ms], and the vertical axis represents the generated voltage [V]. Here, the generated voltages when test resistors of 1 MΩ, 100 kΩ, and 10 kΩ are connected are denoted as V1', V2', and V3', respectively. The open-circuit voltage is denoted as Vop.

[0183] As shown in Figure 31, each generated voltage contains a component that fluctuates significantly at 50 Hz. Each waveform also contains fine vibration components, which are high-order frequency components. The amplitude of each waveform is as follows: Vop is the largest at approximately 70 V, V1' is approximately 45 V, and V2' is approximately 5 V. The amplitude of V3' is very small.

[0184] Figure 32 is a graph showing the frequency characteristics of the generated voltage when the resistance value of the load element 76 in Figure 30 is changed. Figure 32 shows a Fourier transform of the waveform shown in Figure 31, with the horizontal axis of the graph representing frequency [Hz] and the vertical axis representing noise level [dBm]. Here, the noise levels (power) corresponding to V1', V2', V3', and Vop are denoted as P1', P2', P3', and Pop.

[0185] The power Pop, which is equivalent to the open-circuit voltage Vop, is calculated when a high-resistance resistor (e.g., 10 MΩ) that can be considered to be substantially in an open state is connected. Pop is the power generated according to the input resistance of the measuring instrument, for example.

[0186] As shown in Figure 32, the noise level of the stabilized power supply 28c is dominated by noise components at 50 Hz. It can also be seen that the noise level drops sharply when the resistance of the load element 76 is reduced. For example, at a peak of 50 Hz, Pop is 48 W, P1' is 22 W, P2' is 486 mW, and P3' is 4.9 mW. Therefore, the low-frequency side is considered to be in a nonlinear region. On the other hand, in the region above 900 Hz, for example, at a peak around 950 Hz, P3' drops, but Pop, P1', and P2' remain at approximately the same noise levels. This is thought to be because as the frequency increases, the influence of the complex components of the internal resistance of the noise power source 75 decreases, approaching a linear region.

[0187] Thus, the generated voltage (noise level) output from the noise power source 75 also exhibits the same tendency as that of the power generation unit 16. That is, on the low frequency side, when the resistance value of the load element 76 decreases, the generated voltage (noise level) drops sharply, making it difficult to harvest sufficient power.

[0188] From the above measurement results, it is considered that the internal resistance of the noise power source 75 is very high in the low frequency band such as the nonlinear region. Therefore, the inventors considered that an impedance mismatch occurred between the output side of the AC power (the noise power source 75 consisting of the noise source N and the antenna unit 15) and the input side of the AC power (the power generation unit 16 including the rectifier circuit 20 and the load element 76).

[0189] Fig. 33 is a circuit diagram illustrating impedance mismatch in a comparative power harvesting device 510. The circuit shown in Fig. 33 illustrates the circuit configuration of the comparative power harvesting device 510 using a noise power source model, and is a circuit connecting a noise power source 75 and a power generation unit 16. Note that the power generation unit 16 illustrated is a circuit in which the electrostatic protection component 42a, the Zener diode 42b, and the backflow prevention diode 43 of the configuration shown in Fig. 21 are omitted.

[0190] The noise power source 75 is represented by a model in which a noise source N as an AC power supply, a resistance element 81, and a capacitor 82 are connected in series in this order from the second connection part 14b connected to the earth ground 4 to the first connection part 14a. The resistance element 81 and the capacitor 82 are an internal resistance 80 of the noise power source 75. By including the capacitor 82, the internal resistance 80 becomes a resistor having a complex component.

[0191] In the following, the connection boundary between the noise power source 75 and the power generation unit 16 (the connection boundary between the antenna unit 15 and the rectifier circuit 20) is taken as a matching surface, and the output impedance (output resistance) of the noise power source 75 is referred to as Zs, and the input impedance (input resistance) of the power generation unit 16 is referred to as Zin. The output impedance Zs is the impedance of the internal resistance 80.

[0192] 27, 29, 31, and 32, it is believed that the resistance value (output impedance Zs) of the internal resistance 80 of the noise power source 75 is 1 MΩ or more in the nonlinear region. Therefore, in the following, the output impedance Zs in the nonlinear region is assumed to be 2 MΩ. Meanwhile, the resistance value of the load element 76 depends on the type of element, but is approximately 10 kΩ to 100 kΩ for a secondary battery, for example.

[0193] The input impedance Zin of the power generation unit 16 also varies depending on the voltage applied to the diodes 41a to 41d that make up the rectifier circuit 20. For example, when the voltage is equal to or lower than the reference voltage, the input impedance Zin exhibits a very high resistance value. On the other hand, when the voltage is equal to or higher than the reference voltage, the input impedance Zin varies depending on the resistance value of the load element 76 connected downstream of the rectifier circuit 20, and is approximately half the resistance value of the load element 76. Therefore, for example, when a 10 kΩ load element 76 is connected, the input impedance Zin is 5 kΩ.

[0194] In this case, the output impedance Zs of the noise power source 75 is 2 MΩ, while the input impedance Zin of the rectifier circuit is 5 kΩ, resulting in an impedance mismatch, which results in a situation where almost no power can be taken in in low frequency bands such as the nonlinear region.

[0195] Fig. 34 is a circuit diagram showing an example of the configuration of a power harvesting device 520 equipped with a transformer 70. Fig. 34 shows a circuit configuration in which, in addition to the circuit shown in Fig. 33, a transformer 70 is provided as a matching circuit between a noise power source 75 (antenna unit 15) and a power generation unit 16 (rectifier circuit 20). This configuration describes the power harvesting device 520 according to this embodiment using a noise power source model.

[0196] As described with reference to Figure 20, the transformer 70 is connected between the antenna unit 15 and the rectifier circuit 20, and is configured to match the impedance between the antenna unit 15 and the power generation unit 16 including the load element 76 in the target frequency band.

[0197] The target frequency band here is a frequency band in which the amount of decrease in output power of antenna unit 15 exceeds a predetermined threshold when power generation unit 16 including load element 76 is connected to antenna unit 15 with respect to power corresponding to the open-circuit voltage of antenna unit 15. In other words, the characteristics of transformer 70 are set to target a frequency band in which the amount of decrease in output power when power generation unit 16 including load element 76 is connected to noise power source 75 becomes greater than a certain level (predetermined threshold), using the power expected when noise power source 75 (antenna unit 15) is in an open state as a reference.

[0198] By achieving impedance matching in this manner in the target frequency band, it is possible to pass a sufficient current through the power generation unit 16 without reducing the voltage, even when, for example, the output impedance Zs of the noise power source 75 is high and the input impedance Zin of the power generation unit 16 is low. This makes it possible to efficiently harvest power in frequency bands where voltage drops are observed during power harvesting.

[0199] The predetermined threshold value that defines the target frequency band can be set appropriately depending on, for example, the characteristics of the noise source, the resistance value of the load element 76, and the like.

[0200] For example, in the example shown in Figure 32, multiple peaks exceeding 0 dBm (1 mW) are observed. Here, we focus on the power P2' when a 100 kΩ load element 76 is connected. For example, in the region above 900 Hz, P2' is approximately equal to Pop, suggesting almost no power reduction. Looking at the region below 900 Hz, the reduction in P2' relative to Pop for peaks above 0 dBm is at least 30% of the graph value. For example, at the 850 Hz peak, where power reduction is relatively small, the Pop power level is approximately 2.2 mW (3.5 dBm), while the P2' power level is approximately 1.5 mW (1.8 dBm), a reduction of approximately 32%. Note that the reduction in P2' relative to Pop is even greater for peaks at lower frequencies. Therefore, the predetermined threshold is set to 30% of the graph value of the power Pop, which corresponds to the open-circuit voltage. This makes it possible to improve yields, for example, for peaks that appear at frequencies close to the linear region.

[0201] The predetermined threshold is not limited to this and may be set to a higher value. For example, the predetermined threshold may be 50% of the graph value of the power corresponding to the open-circuit voltage, or may be 90% of the graph value of the power corresponding to the open-circuit voltage. For example, if the threshold is set to 90% of the graph value, it becomes possible to improve the harvesting efficiency in a region where almost no power is harvested when the load element 76 is connected, and it becomes possible to achieve a significant increase in the harvest yield.

[0202] Furthermore, when the power generation unit 16 including the load element 76 is directly connected to the antenna unit 15 (noise power source 75), a nonlinear region and a linear region also appear in the output of the antenna unit 15. In this case, the linear region seen in the output of the antenna unit 15 can be said to be the frequency band where the ratio of the output voltage of the antenna unit 15, which occurs when the resistance value of the power generation unit 16 including the load element 76 is changed, converges. Furthermore, the nonlinear region seen in the output of the antenna unit 15 can be said to be the frequency band lower than the linear region, where the change in the ratio of the output voltage with respect to frequency is larger than in the linear region. In this embodiment, the linear region corresponds to the first frequency band, and the nonlinear region corresponds to the second frequency band.

[0203] The target frequency band described above is typically a nonlinear region. That is, the transformer 70 performs impedance matching in a low-frequency region where the voltage is very small when the power generating unit 16 is connected. This allows for efficient power harvesting from a region where almost no power could be harvested when the power generating unit 16 is directly connected to the antenna unit 15.

[0204] The target frequency band is a frequency band that includes, as frequency components of the electromagnetic noise generated by the noise source N, quasi-electrostatic field components of the electromagnetic waves radiated from the noise source N or induced electromagnetic field components induced by current flowing through the noise source N. The quasi-electrostatic field and induced electromagnetic field components are, for example, low-frequency components of 30 MHz or less, which are components of conducted noise. The target frequency band is set to a frequency range in which such low-frequency components can be harvested. This makes it possible to efficiently harvest the quasi-electrostatic field and induced electromagnetic field components.

[0205] Furthermore, it is believed that the resistance value of the power generating unit 16 including the load element 76 in the target frequency band (the input impedance Zin of the power generating unit 16 in the target frequency band) greater than a certain level is less likely to cause a drop in voltage and higher power harvesting efficiency. From this perspective, the resistance value of the power generating unit 16 including the load element 76 in the target frequency band is preferably 1 kΩ or greater. This, combined with the effect of the transformer 70, enables appropriate power harvesting even in regions where little power has previously been harvested. Furthermore, the resistance value of the power generating unit 16 including the load element 76 in the target frequency band is more preferably 10 kΩ or greater, and even more preferably 30 kΩ or greater. For example, by setting the resistance value to 30 kΩ or greater, it is possible to sufficiently improve the amount of power harvested in low frequency bands.

[0206] 35 is a schematic diagram showing an example configuration of the transformer 70. A specific example configuration of the transformer 70 will be described below. Here, it is assumed that the output impedance Zs of the noise power source 75 in the target frequency band is 2 MΩ, and the input impedance Zin of the power generation unit 16 is 5 kΩ. In this case, the resistance ratio (Zs:Zin) of the output impedance Zs to the input impedance Zin is 400:1.

[0207] The transformer 70 can compensate for such a large difference in resistance by utilizing the difference in the number of turns and resistance of the primary coil 72 and the secondary coil 74. This method is also applied to a matching transformer that connects an amplifier and a speaker in audio equipment, for example.

[0208] Here, the winding ratio of the primary coil 72 and the secondary coil 74 is expressed as n:1. In this case, the impedance ratio of the primary coil 72 and the secondary coil 74 is n:1. 2 :1. Therefore, the appropriate turns ratio corresponding to Zs:Zin = 400:1 is 20:1. By using a transformer 70 configured with such a turns ratio, it is possible to achieve appropriate impedance matching. Below, a configuration using a transformer 70 with a turns ratio close to 20:1 will be described.

[0209] Fig. 36 is a circuit diagram showing an example of the configuration of a power harvesting device using a single transformer. Fig. 37 is a circuit diagram showing an example of the configuration of a power harvesting device using three transformers. Here, the stabilized power supply 28c shown in Fig. 30 etc. was used as an example of the electrical device 28. Furthermore, test resistors of 1 kΩ and 10 kΩ, which have large voltage changes, were used as the load element 76.

[0210] The transformer 70 shown in Fig. 36 is an audio resistance conversion transformer. The impedance of the primary coil 72 in the audio band (e.g., 20 Hz to 20 kHz) is 300 kΩ, and the impedance of the secondary coil 74 is 1 kΩ. The DC resistance of the primary coil 72 is 3.6 kΩ, and the DC resistance of the secondary coil 74 is 63 Ω. The ratio of the primary coil 72 to the secondary coil is 17.91:1.

[0211] The power harvesting device 520 shown in Fig. 37 is formed by connecting three transformers 70 shown in Fig. 36. In Fig. 37, the primary coils 72 of the three transformers 70 are connected in series, and the antenna unit 15 (first connection portion 14a and second connection portion 14b) is connected to both ends of the series. Similarly, the secondary coils 74 of the three transformers 70 are connected in series, and the rectifier circuit 20 (input terminal 44a and input terminal 44b) is connected to both ends of the series.

[0212] 36 and 37, the voltage V, current I, and power W were measured for a frequency peak of 50 Hz. The measurement results are shown in Table (1). ...Table (1)

[0213] When the transformer 70 was not connected, and the load element 76 was 1 kΩ, V=0.05 V. When the load element 76 was 10 kΩ, V=0.46 V. Thus, when the transformer 70 was not connected, only a very small induced voltage was obtained.

[0214] In the configuration shown in Figure 36 with one transformer 70 connected, when the load element 76 was 1 kΩ, V = 0.18 V. When the load element 76 was 10 kΩ, V = 0.56 V. Furthermore, compared to when the transformer 70 was not connected, the power when the load element 76 was 1 kΩ increased from 2.5 μW to 32.4 μW, and the power when the load element 76 was 10 kΩ increased from 21.2 μW to 31.4 μW. In this way, it was found that by connecting the transformer 70, the power yield improved for both the 1 kΩ and 10 kΩ load elements 76.

[0215] However, while the primary impedance Zs of the noise power source 75 is very high, the resistance value (3.6 kΩ) of the primary coil 72 of one transformer 70 is very low, so there is a possibility that the effect of impedance matching is not fully achieved.

[0216] The power harvesting device 520 shown in Figure 37 increases the total resistance of the primary coil 72 by increasing the number of transformers 70. In this case, because the transformers 70 with the same turns ratio are connected in series, the overall turns ratio remains unchanged. Meanwhile, the DC resistance of the primary coil 72 is tripled to 10.8 kΩ. Similarly, the DC resistance of the secondary coil 74 is 189 Ω.

[0217] In this configuration with three transformers 70 connected, when the load element 76 was 1 kΩ, V = 0.5 V. When the load element 76 was 10 kΩ, V = 2.22 V. Furthermore, compared to when no transformer 70 was connected, the power when the load element 76 was 1 kΩ increased from 2.5 μW to 250 μW, and when the load element 76 was 10 kΩ, the power increased from 21.2 μW to 493 μW. In this way, the voltage and power increased significantly, making it possible to significantly improve the harvest yield.

[0218] In this way, the turns ratio and resistance value of the transformer 70 are set based on the internal resistance 80 (output impedance Zs) of the antenna unit and the resistance value (input impedance Zin) of the power generation unit 16 including the load element 76 in the target frequency band. For example, the turns ratio (n:1) is set to achieve Zs:Zin. Also, for example, the resistance value of the primary coil 72 of the transformer 70 is set to approach the output impedance Zs. Alternatively, the resistance value of the secondary coil 74 may be set based on the input impedance Zin. This makes it possible to sufficiently improve the harvesting efficiency in the target frequency band.

[0219] FIG. 38 is a graph showing the charging characteristics of a secondary battery using the power harvesting device 520. FIG. 39 is a graph showing the discharging characteristics of a secondary battery charged by the power harvesting device 520. In this measurement, a power harvesting device 520 shown in FIG. 37 in which three transformers 70 are connected in series was used to confirm whether a secondary battery serving as a load element 76 could actually be charged. A stabilized power supply 28c was used as the electrical device 28 serving as the noise source N. A lithium-ion battery with a capacity of 4 mAh was used as the secondary battery. For comparison, a similar measurement was performed using a comparative power harvesting device 510 to which no transformer 70 was connected.

[0220] The charging characteristics shown in Figure 38 show the time variation of the voltage (charging voltage) across the secondary battery. In Figure 38, the charging characteristics when using the power harvesting device 520 are denoted as 520a, and the charging characteristics when using the comparative power harvesting device 510 are denoted as 510a. Here, the secondary battery was charged for three hours using the power harvesting device 520 and the comparative power harvesting device 510. With the comparative power harvesting device 510, the initial voltage rose only to about 1.2V, and the final voltage was about 2V. The charging voltage also did not show any convergence. On the other hand, with the power harvesting device 520, the initial voltage rose to 1.6V, and then the charging voltage rose to exceed 2V and converge to around 2.4V within about 15 minutes.

[0221] The discharge characteristics shown in Figure 39 show the time change in the voltage across the secondary battery (battery voltage) when a 1 kΩ resistor is connected to the secondary battery and the battery is discharged. In Figure 39, the discharge characteristics when using the power harvesting device 520 are denoted as 520b, and the discharge characteristics when using the comparative power harvesting device 510 are denoted as 510b. The secondary battery receiving power using the comparative power harvesting device 510 without the transformer 70 exhibited a rapid voltage drop immediately after the start of discharge and was fully discharged in about 10 minutes. In contrast, the secondary battery charged by the power harvesting device 520 maintained a high voltage for about 15 minutes. Thereafter, the battery voltage decreased and was fully discharged in about 30 minutes. As such, it was found that the comparative power harvesting device 510 without the transformer 70 was barely able to charge the secondary battery, whereas the power harvesting device 520 equipped with the transformer 70 was able to properly charge the secondary battery.

[0222] In this way, it is now possible to harvest power from low frequency bands, such as the nonlinear region, which would be difficult to charge with a device without the transformer 70. In the above measurements, the turns ratio of the transformer 70 matched the Zs:Zin ratio, but the resistance value of the primary coil 72 was lower than Zs (10.8 kΩ). Increasing this value is expected to further improve the harvesting efficiency. Ideally, the resistance value of the primary coil 72 should match the output impedance Zs of the noise power source 75, and the resistance value of the secondary coil 74 should match the input impedance Zin of the power generation unit 16. Based on this principle, appropriate settings of the turns ratio and resistance value of the transformer 70 can improve the harvesting efficiency.

[0223] 20 and 21 , the sensing device 500 according to this embodiment also has a transformer 70 configured in the same manner as the above-described power harvesting device 520. That is, the transformer 70 mounted on the sensing device 500 is set according to the characteristics of the antenna unit 15 provided near the high-voltage line 1.

[0224] For example, the target frequency band for the sensing device 500 is the frequency band in which the amount of reduction in output power of the antenna unit 15 when the power generation unit 16 including the load element 76 is connected to the antenna unit 15 exceeds a predetermined threshold (e.g., 30% of the graph value of the power equivalent to the open-circuit voltage) relative to the power equivalent to the open-circuit voltage of the antenna unit 15 provided near the high-voltage line 1. The turns ratio and other factors of the transformer 70 are set so that impedance matching can be achieved in such a target frequency band. This makes it possible to highly efficiently harvest electromagnetic noise radiated from the high-voltage line 1.

[0225] In particular, because the AC current flowing through the high-voltage line 1 has a relatively low frequency, the main components contained in the electromagnetic noise are low-frequency components. In contrast, by configuring the transformer 70 to target the target frequency band as described above, it is possible to efficiently harvest low-frequency components with high power peaks without damaging them. As a result, the amount of power harvested near the high-voltage line 1 is significantly increased, enabling the sensing device 500 to operate stably.

[0226] In the above-described power harvesting from the high-voltage line 1, because the high-voltage line 1 is a noise source N, it is not possible to directly connect antenna elements such as the first conductor 11 and the second conductor 12. However, in such an environment, noise present in the space surrounding the high-voltage line 1 can be harvested as power, making it possible to configure the sensing device 500 with multiple power harvesting sections (e.g., sections excluding the sensing unit 17). In other words, if current is required, the current can be increased by connecting multiple power harvesting sections in parallel. If voltage is required, a higher voltage can be generated by connecting multiple power harvesting sections in series. Furthermore, with parallel connections, the voltage of each power harvesting section may not be constant, potentially resulting in failure. In this case, multiple units can be used while switching between them as needed. This improves the reliability of the sensing device 500.

[0227] 40 is a schematic diagram showing a configuration example of a sensing device according to a sixth embodiment. In this embodiment, an example will be described in which a sensing device 600 including a transformer 70 is applied to a power transmission facility 5a that transmits electric power. The power transmission facility 5a has a power transmission line 2, which is a high-voltage line 1, and a steel tower 6. The power transmission facility 5a is an example of a facility 5 associated with the high-voltage line 1. In the power transmission facility 5a, the power transmission line 2 corresponds to a noise source N.

[0228] The sensing device 600 has an antenna element 10, an antenna unit 15, a transformer 70, a power generation unit 16 including a rectifier circuit 20 and a load element 76, and a sensing unit 17. As described with reference to Fig. 20 , the sensing unit 17 may be the load element 76. The basic configurations of the antenna unit 15, the transformer 70, and the power generation unit 16 are similar to those of the sensing device 500 described in the fifth embodiment, for example.

[0229] The antenna element 10 is an antenna element included in the sensing device 600. As described with reference to Fig. 3, a rod antenna or a cable antenna is used as the antenna element 10. The specific configuration of the antenna element 10 is not limited, and other antenna elements 10 such as a patch antenna may also be used.

[0230] 40 , the first conductor 11 is the antenna element 10. The second conductor 12 is the steel tower 6 grounded to the earth ground 4. The antenna element 10 can be regarded as a metal body that is capacitively coupled to the metal part (steel tower 6) of the power transmission facility 5 a.

[0231] The first connection portion 14a of the antenna portion 15 is connected to the antenna element 10. The second connection portion 14b is connected to a metal part of the steel tower 6. The second connection portion 14b can be connected to the steel tower 6 by, for example, screwing, crimping, welding, or the like.

[0232] Generally, a transmission line 2 supported by a steel tower 6 transmits AC power at 50 Hz or 60 Hz. Therefore, near the steel tower 6 (transmission line 2), basically no leakage electric field other than that of the AC power frequency is generated. Therefore, in the sensing device 600, in an antenna configuration such as that shown in Figure 40, the characteristics of the transformer 70 are set so that impedance matching can be achieved in the 50 Hz band or the 60 Hz band. This makes it possible to significantly improve the harvesting efficiency of the leakage electric field from the transmission line 2.

[0233] Fig. 41 is a schematic diagram showing an example of the configuration of a sensing device with surge protection. Sensing device 601 is the sensing device 600 shown in Fig. 40 with a surge protection element 85 added. The surge protection element 85 is an element that has high resistance under normal voltages but becomes low resistance when a high voltage such as a lightning surge is applied, and has the function of dissipating overcurrent. For example, a ZnO element or the like is used as the surge protection element 85. Alternatively, any element that has the function of dissipating current when a high voltage is applied may be used.

[0234] The surge protection element 85 is provided so as to connect at least one of the two wirings (the first connection part 14a or the second connection part 14b) constituting the antenna part 15 to the GND potential. This makes it possible to release an overcurrent to the earth ground 4 when a high voltage is applied to the first connection part 14a or the second connection part 14b.

[0235] 41 , one end of the surge protection element 85 is connected to the middle of the second connection part 14b connected to the pylon 6, and the other end of the surge protection element 85 is connected to the pylon 6. As a result, when a high voltage is applied to the second connection part 14b, for example, the surge protection element 85 has low resistance, and a path is formed to return the overcurrent to the pylon 6 connected to the earth ground 4. This makes it possible to prevent an overcurrent from flowing through the sensing device 601 and damaging the element.

[0236] Seventh Embodiment Fig. 42 is a schematic diagram showing a configuration example of a sensing device according to a seventh embodiment. In this embodiment, an example will be described in which a sensing device 700 including a transformer 70 is applied to an electric train track facility 5b on which trains run. The electric train track facility 5b has an electric wire 3 and a rail 8. In the electric train track facility 5b, the electric wire 3 corresponds to a noise source N.

[0237] The electric train line 3 is, for example, an overhead line for transmitting electricity that is stretched above rails 8 on which trains run. The electric train line 3 is fixed to supports for overhead power transmission lines, such as concrete pillars or steel portal towers, via insulators or the like. The rails 8 are, for example, formed by arranging columnar metal members of a predetermined length. The rails 8 are installed on the ground or via an elevated bridge, for example, via sleepers or the like.

[0238] The following mainly describes the case where the rail 8 is not grounded and is laid in a state where it is electrically floating from the earth ground 4. The case where the rail 8 is grounded to the earth ground 4 will be described later with reference to Fig. 45 etc.

[0239] In this embodiment, an explanation will be given mainly by taking as an example an electric contact line facility 5b installed on a DC electrified line. Therefore, the electric contact line 3 is a high-voltage line that transmits DC power. For example, in Japan, the voltage applied to the electric contact line 3 is mainly 1500 V. Note that the voltage of the electric contact line 3 is not particularly limited, and the present technology can also be applied to an electric contact line facility 5b that uses other DC voltages.

[0240] DC power rectified at a substation is supplied to the electric power line 3. This DC power is generally rectified using a three-phase full-wave rectifier circuit, and is known to contain frequency components six times the power supply frequency (50 Hz or 60 Hz). That is, the DC power flowing through the electric power line 3 contains a frequency component of 50 Hz x 6 = 300 Hz or a frequency component of 60 Hz x 6 = 360 Hz. The sensing device 700 is configured to harvest power induced by electromagnetic noise in such a low-frequency band.

[0241] The sensing device 700 has a connecting metal plate 86, an insulating member 87, a grounding member 88, an antenna unit 15, a transformer 70, and a power generating unit 16 including a rectifier circuit 20 and a load element 76. The basic configurations of the antenna unit 15, the transformer 70, and the power generating unit 16 are similar to those of the sensing device 500 described in the fifth embodiment, for example.

[0242] The connecting metal plate 86 is a metal plate for capacitive coupling to the rail 8, which is a metal part of the contact line facility 5b. A copper plate or the like is used as the connecting metal plate 86. The insulating member 87 is a member that insulates the connecting metal plate 86 from the rail 8. An insulating sheet or the like made of an insulating material is used as the insulating member 87. Note that an insulating film applied to the connecting metal plate 86, an insulating adhesive, or the like may also be used as the insulating member 87.

[0243] 42, the connecting metal plate 86 is attached to the rail 8 via an insulating member 87. The method for attaching the connecting metal plate 86 is not limited, and a predetermined holder or the like may be used, or the connecting metal plate 86 may be fixed with screws, adhesive, or the like.

[0244] The earth member 88 is a member that is grounded to the earth ground 4. For example, a metal anchor that is driven into the ground may be used, or a clip, a crimp terminal, or the like may be used to connect to a metal body that is already grounded to the earth ground 4.

[0245] 42 , the first conductor 11 is a connecting metal plate 86. The second conductor 12 is an earth member 88 grounded to the earth ground 4. In this case, the connecting metal plate 86 can be regarded as a metal body that is capacitively coupled to the metal part (rail 8) of the contact point equipment 5b.

[0246] As described above, the electric train wires 3 transmitting DC power are a noise source N that generates electromagnetic noise containing frequency components six times the power supply frequency (300 Hz or 360 Hz). Therefore, in the sensing device 700, in the antenna configuration shown in Fig. 42, the characteristics of the transformer 70 are set so as to achieve impedance matching in the 300 Hz band or the 360 ​​Hz band. This makes it possible to significantly improve the harvesting efficiency of the electric field leaking from the electric train wires 3.

[0247] Furthermore, in the contact rail facility 5b, a predetermined signal may be transmitted to the rail 8. For example, in a method called a track circuit, a signal for detecting the position of a train or the like is supplied to the rail 8. In this regard, by applying the present technology, the above-mentioned low-frequency band noise appearing on the rail 8 is converted into electric power, making it possible to suppress the noise level of the rail 8, for example. This makes it possible to improve the noise-to-noise ratio of signal transmission using the rail 8.

[0248] Fig. 43 is a schematic diagram showing an example of the configuration of a sensing device with surge protection. A sensing device 701 is configured by adding a surge protection element 85 to the sensing device 700 shown in Fig. 42. The surge protection element 85 may be, for example, a ZnO element.

[0249] For example, rails 8 placed outdoors may be struck by lightning directly or via a train. To protect against surges in this case, a surge protection element 85 is provided. Here, the surge protection element 85 is connected between the first connection portion 14a and the earth ground 4. As a result, when lightning strikes, excess current that flows into the first connection portion 14a is released to the earth ground 4 via the surge protection element 85. This makes it possible to prevent damage to the element due to a lightning strike.

[0250] Figure 44 is a schematic diagram showing an example of connection between a sensing device and a rail. The sensing device 702 shown in Figure 44 is a device designed for use in cases where it is difficult to ground the device to the earth ground 4, such as on a railway bridge. The sensing device 702 is provided with an insulated cable 89 instead of the earth member 88 of the sensing device 700 shown in Figure 42, for example. The insulated cable 89 is a metal cable with an insulating coating, and is provided so as not to short-circuit to the rail 8. The insulated cable 89 is arranged, for example, near the rail 8 and along the rail 8, but can be provided as appropriate to suit the structure around the rail 8.

[0251] 44, the first conductor 11 is a connecting metal plate 86. The second conductor 12 is an insulated cable 89. In this case, the insulated cable 89 can be regarded as a metal body having a different potential from that of the rail 8, which is a metal part of the contact point facility 5b.

[0252] In this way, when it is difficult to ground the antenna to the earth ground 4, an electric field antenna can be configured by using a metal body, such as the insulated cable 89, that has a different potential from the rail 8. Furthermore, by lengthening the insulated cable 89, the antenna size can be increased, and the amount of power that can be received can be improved. With this configuration, it is possible to properly harvest power even in an environment where it is difficult to ground the antenna to the earth ground 4, such as a railway bridge.

[0253] Fig. 45 is a schematic diagram showing an example of connection between a sensing device and a rail. The sensing device 703 shown in Fig. 45 is a device used in an environment where the rail 8 is grounded to the earth ground 4. As described above, in Japan, the rail 8 is not grounded but is floating above the earth ground 4. On the other hand, in some countries, the rail 8 is installed while being grounded to the earth ground 4.

[0254] When the rail 8 is grounded to the earth ground 4 in this way, the insulated cable 89 that is not short-circuited to the rail 8 or the earth ground 4 may be used as the antenna element. At the same time, the rail 8 itself may be used as the earth ground 4. For example, a connecting metal plate 86 is electrically connected to the rail 8 without an insulating sheet or the like, and the antenna unit 15 (second connecting portion 14b) and the rail 8 are connected via the connecting metal plate 86. In this case, the connecting metal plate 86 functions as a metal part for connecting to the rail 8.

[0255] 45 , the first conductor 11 is an insulated cable 89. The second conductor 12 is a rail 8 grounded to the earth ground 4. In this case, the insulated cable 89 can be regarded as a metal body that is capacitively coupled with the rail 8, which is a metal part of the contact point track facility 5b.

[0256] The insulated cable 89 is capacitively coupled to the rail 8, and also to the electric wire 3, which is the noise source N. This makes it possible to configure an electric field antenna near the electric wire 3, even when the rail 8 is grounded, and makes it possible to harvest power appropriately.

[0257] Other Embodiments The present technology is not limited to the above-described embodiments, and various other embodiments can be realized.

[0258] In the above, examples of high-voltage lines have been described using power transmission lines supported by steel towers and electric train lines that supply power to trains, but the present technology may also be applied to other high-voltage lines. For example, the voltage of the high-voltage line 1 may be at least higher than the voltage level (e.g., 100 V or 200 V) of a distribution line that supplies power to ordinary households. By using such high-voltage lines 1 with a high voltage level, efficient power harvesting is possible.

[0259] Furthermore, the voltage of the high-voltage line 1 to which this technology is applied is, for example, 500 V or higher. This increases the amount of electric field energy harvested compared to general power distribution lines, making it possible to, for example, operate a sensing device stably. Note that the voltage range of the high-voltage line 1 is not limited, and this technology can also be applied to transmission lines with a lower voltage range depending on, for example, the purpose and use of the sensing device, the power harvesting efficiency, etc.

[0260] In the above embodiment, the description is mainly given of an overhead high-voltage line that is placed above the ground. However, the present technology is not limited to this, and may be applied to a high-voltage line laid underground. Also, the present technology may be applied to a high-voltage line placed above ground, such as a third track of a train.

[0261] The sensing device based on this technology converts electromagnetic noise generated from high-voltage lines into electricity, which can supply power to sensors, control devices, communication devices, etc., enabling efficient energy use. Therefore, the sensing device based on this technology can be related to Goal 7, "Affordable and Clean Energy," of the Sustainable Development Goals (SDGs) adopted at the United Nations Summit in 2015.

[0262] It is also possible to combine at least two of the features of the present technology described above. That is, the various features described in each embodiment may be arbitrarily combined without distinguishing between the embodiments. Furthermore, the various effects described above are merely examples and are not intended to be limiting, and other effects may also be achieved.

[0263] In the present disclosure, the terms "same," "equal," "orthogonal," etc. are concepts that include "substantially the same," "substantially equal," "substantially orthogonal," etc. For example, they also include states that fall within a predetermined range (e.g., a range of ±10%) based on "completely the same," "completely equal," "completely orthogonal," etc.

[0264] The present technology can also be configured as follows. (1) A sensing device comprising: an antenna unit connected to a first conductor and a second conductor, respectively, that are provided near a high-voltage power line for transmitting electricity and generate a potential difference between them, and that form an antenna using the first conductor and the second conductor; a power generation unit that harvests the output of the antenna unit as power; and a sensing unit that is driven by power from the power generation unit and performs a detection operation to detect the state of related equipment of the high-voltage line or the surrounding environment using a predetermined sensor. (2) The sensing device according to (1), wherein the sensing unit comprises a control unit that controls the detection operation and a communication unit that performs communication related to the detection operation. (3) The sensing device according to either (1) or (2), wherein the sensing unit has the predetermined sensor. (4) The sensing device according to any one of (1) to (3), wherein the antenna unit is disposed between the power generation unit and an antenna formed by the first conductor and the second conductor, and includes a protection circuit that protects the power generation unit from a lightning surge. (5) The sensing device according to (4), wherein the protection circuit includes a transformer or a fuse. (6) The sensing device according to any one of (1) to (5), wherein the power generation unit has a storage element that stores power harvested from the output of the antenna unit, and the sensing unit is driven by power from the storage element. (7) The sensing device according to (6), wherein the sensing unit detects whether or not power is being transmitted through the high-voltage line based on a power harvesting state in the power generation unit, and transmits the detection result to an external device. (8) The sensing device according to any one of (1) to (7), wherein the voltage of the high-voltage line is equal to or greater than 500 V. (9) The sensing device according to any one of (1) to (8), wherein at least one of the first conductor and the second conductor is a metal body constituting an equipment related to the high-voltage line.(10) The sensing device according to (9), further comprising an antenna element provided near the high-voltage line, wherein the first conductor is the antenna element, and the second conductor is a metal body constituting the related equipment. (11) The sensing device according to (10), wherein the antenna element is a rod antenna, a cable antenna, or an earth member connected to earth ground. (12) The sensing device according to (10) or (11), wherein the antenna length of the antenna element is set so that the power output from the antenna unit is equal to or less than a predetermined threshold. (13) The sensing device according to any one of (9) to (12), wherein the high-voltage line is a power transmission line supported by a steel tower, the second conductor is the steel tower, the first conductor is an antenna element provided so as to be electrically floating from the steel tower, and the predetermined sensor detects a state of power transmission equipment including the power transmission line and the steel tower or a state of the surrounding environment of the power transmission equipment. (14) The sensing device according to any one of (9) to (12), wherein the high-voltage line is an electric train line that supplies power to a train, the second conductor is a metal part of the train, and the first conductor is an antenna element provided on the train so as to be electrically floating from the metal part of the train, and the predetermined sensor detects a running state of the train or a state of the surrounding environment of the train. (15) The sensing device according to any one of (9) to (12), wherein the high-voltage line is an electric train line that supplies power to a train, the second conductor is a rail on which the train runs, the first conductor is either an antenna element electrically floating from the rail that serves as the second conductor, or another rail different from the rail that serves as the second conductor, and the predetermined sensor detects the state of wayside facilities including the rail or the state of the environment surrounding the wayside facilities.(16) The sensing device according to any one of (1) to (15), wherein the high-voltage line transmits AC power, and the power generation unit has a rectifier circuit that rectifies received AC power induced between the first conductor and the second conductor by the AC power. (17) The sensing device according to any one of (1) to (15), wherein the high-voltage line transmits DC power, and the power generation unit has a storage circuit that stores received DC power that flows due to a potential difference induced between the first conductor and the second conductor by the DC power. (18) The sensing device according to any one of (1) to (17), wherein the power generation unit has a rectifier circuit that rectifies AC power output from the antenna unit and is configured to supply output from the rectifier circuit to a load element, and further comprises a transformer connected between the antenna unit and the rectifier circuit, for achieving impedance matching between the antenna unit and the power generation unit including the load element in a target frequency band in which a reduction in output power of the antenna unit when the power generation unit including the load element is connected to the antenna unit exceeds a predetermined threshold with respect to power corresponding to an open-circuit voltage of the antenna unit. (19) The sensing device according to (18), wherein the load element is either the sensing unit or a storage element provided in the power generation unit that drives the sensing unit. (20) The sensing device according to (18) or (19), wherein the predetermined threshold is 30% of power corresponding to the open-circuit voltage.

[0265] REFERENCE SIGNS LIST 1... High voltage line 5... Related equipment 10... Antenna element 11... First conductor 12... Second conductor 15... Antenna section 16... Power generation section 17... Sensing section 18, 18a, 18b... Protection circuit 20... Rectifier circuit 22... Storage element 26... Status sensor 70... Transformer 100, 200, 300, 301, 302, 400, 500, 600, 601, 700, 701, 702, 703... Sensing device

Claims

1. A sensing device comprising: an antenna unit that is connected to a first conductor and a second conductor that are provided near a high-voltage power line and generate a potential difference between them, and that forms an antenna using the first conductor and the second conductor; a power generation unit that harvests the output of the antenna unit as power; and a sensing unit that is driven by power from the power generation unit and performs a detection operation to detect the state of related equipment or the surrounding environment of the high-voltage line using a specified sensor.

2. A sensing device according to claim 1, wherein the sensing unit has a control unit that controls the detection operation, and a communication unit that performs communication related to the detection operation.

3. A sensing device according to claim 1, wherein the sensing unit has the predetermined sensor.

4. A sensing device according to claim 1, wherein the antenna section is disposed between the power generating section and an antenna formed by the first conductor and the second conductor, and has a protection circuit that protects the power generating section from lightning surges.

5. The sensing device according to claim 4, wherein the protection circuit includes a transformer or a fuse.

6. A sensing device according to claim 1, wherein the power generating unit has a storage element that stores power harvested from the output of the antenna unit, and the sensing unit is driven by power from the storage element.

7. A sensing device according to claim 6, wherein the sensing unit detects whether or not power is being transmitted through the high-voltage line based on the state of power harvesting in the power generation unit, and transmits the detection result to an external device.

8. A sensing device according to claim 1, wherein the voltage of the high-voltage line is 500V or higher.

9. A sensing device according to claim 1, wherein at least one of the first conductor and the second conductor is a metal body that constitutes equipment related to the high-voltage line.

10. A sensing device according to claim 9, further comprising an antenna element provided in the vicinity of the high-voltage line, the first conductor being the antenna element, and the second conductor being a metal body constituting the related equipment.

11. A sensing device according to claim 10, wherein the antenna element is a rod antenna, a cable antenna, or an earth member connected to the earth ground.

12. A sensing device according to claim 10, wherein the antenna length of the antenna element is set so that the power output from the antenna section is equal to or less than a predetermined threshold value.

13. A sensing device as described in claim 9, wherein the high-voltage line is a power transmission line supported by a steel tower, the second conductor is the steel tower, the first conductor is an antenna element arranged so as to be electrically floating from the steel tower, and the specified sensor detects the state of the power transmission equipment including the power transmission line and the steel tower or the state of the environment surrounding the power transmission equipment.

14. A sensing device as described in claim 9, wherein the high-voltage line is an electric train line that supplies power to a train, the second conductor is a metal part of the train, the first conductor is an antenna element provided on the train so as to be electrically floating from the metal part of the train, and the specified sensor detects the running state of the train or the state of the environment surrounding the train.

15. A sensing device as claimed in claim 9, wherein the high-voltage line is an electric train line that supplies power to a train, the second conductor is a rail on which the train runs, the first conductor is either an antenna element electrically floating from the rail that serves as the second conductor, or another rail different from the rail that serves as the second conductor, and the specified sensor detects the state of wayside facilities including the rail or the state of the environment surrounding the wayside facilities.

16. A sensing device according to claim 1, wherein the high-voltage line transmits AC power, and the power generation unit has a rectifier circuit that rectifies received AC power induced between the first conductor and the second conductor by the AC power.

17. A sensing device according to claim 1, wherein the high-voltage line transmits DC power, and the power generation unit has a storage circuit that stores received DC power that flows due to a potential difference induced between the first conductor and the second conductor by the DC power.

18. A sensing device as claimed in claim 1, wherein the power generation unit has a rectifier circuit that rectifies AC power output from the antenna unit and is configured to supply the output from the rectifier circuit to a load element, and further comprises a transformer connected between the antenna unit and the rectifier circuit to achieve impedance matching between the antenna unit and the power generation unit including the load element in a target frequency band in which the amount of reduction in the output power of the antenna unit when the power generation unit including the load element is connected to the antenna unit exceeds a predetermined threshold value with respect to power equivalent to the open circuit voltage of the antenna unit.

19. A sensing device according to claim 18, wherein the load element is either the sensing unit or a storage element provided in the power generation unit for driving the sensing unit.

20. A sensing device according to claim 18, wherein the predetermined threshold is 30% of the power corresponding to the open-circuit voltage.

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