Monitoring system and monitoring method

Abstract

To provide a monitoring system and a monitoring method, which improve suppression force to theft of wiring and can reduce damage of theft.SOLUTION: A monitoring system 100 includes: a solar battery 2; a power conditioner 3 including an inverter 3a; a wiring 4 for electrically connecting the solar battery 2 and the power conditioner 3a; a power supply part 7 which can output current to the wiring 4; a monitoring part 8 which is electrically connected to the power supply part 7 and monitors a connection state of the wiring 4 by using the current, when it is brought into a conduction state by a switching part 9 which can switch between the conduction state in which the monitoring part is electrically connected to the wiring 4 and a non-conduction state in which the monitoring part is not electrically connected to the wiring 4; and a control part 10 which switches to the conduction state by the switching part 9 within prescribed time including sunset and constantly or intermittently outputs current to the wiring 4 from the power supply part 7.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a monitoring system and a monitoring method. [Background technology]

[0002] 2. Description of the Related Art In recent years, solar power generation has been attracting attention as a renewable energy source for realizing a sustainable society, and solar power generation facilities are being constructed all over the country.

[0003] Generally, a solar power generation facility consists of solar cells that receive sunlight and generate electricity, a power supply facility equipped with a power conditioner that converts the electromotive force generated by the solar cells from DC power to AC power, and wiring that connects the solar cells to the power supply facility.

[0004] In medium to large-scale solar power generation facilities, the locations where the solar cells are installed and the power supply equipment are often physically separated, for example, by tens to hundreds of meters. Therefore, the wiring connecting the solar cells and the power supply equipment is laid over a long distance. Copper wire, which has high electrical conductivity, is usually used for the wiring.

[0005] Due to the soaring price of copper, the material for this copper wire, theft of copper wires has been occurring all over the country. In particular, solar power generation facilities, which lay wiring (copper wires) over long distances, have been severely damaged, and the damage is increasing year by year. The theft of wiring (copper wires) from solar power generation facilities not only causes losses to the operators of the solar power generation facilities, but also halts the power supply at the solar power generation facilities, hindering the stable supply of energy and potentially having a significant impact on the lives of the people and social and economic activities. Therefore, preventing the theft of wiring from solar power generation facilities is an urgent issue for the stable supply of power from solar power generation facilities and for the realization of a sustainable society.

[0006] To date, a measuring instrument and a measuring method have been disclosed that can measure the insulation resistance and capacitance downstream of the attachment point of a clamp that detects current in the DC circuit of a DC power supply system while the line is still live, using a coupling capacitor and an AC power supply (Patent Document 1).

[0007] By adopting this configuration, since the capacitance of the solar cell is much larger than the capacitance of the wiring connecting the solar cell to the power conditioner, it is possible to detect a break in the wiring when the capacitance value falls below the value before the break by using a mechanism that disconnects the capacitance of the solar cell mentioned above when the wiring is broken. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2012-233825 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, a solar cell is generally composed of a plurality of solar cell modules, and the capacitance of each solar cell module is collected and input to a power conditioner. Therefore, in the above-mentioned configuration, although the capacitance collected from the plurality of solar cell modules can be measured, the capacitance of each solar cell module cannot be measured. Therefore, even if the wiring of each solar cell module is stolen, if the collected capacitance of the plurality of solar cell modules becomes equal to or exceeds the disconnection judgment value, the disconnection cannot be detected, and the theft of the wiring will be overlooked.

[0010] The present invention solves at least part of the above problems, and can contribute to making it easier to monitor the wiring used in a solar power generation system against theft and to increasing the immediacy of identifying a theft incident. Furthermore, the present invention can greatly contribute to a stable power supply by serving as an effective deterrent against theft of the wiring. [Means for solving the problem]

[0011] One monitoring system of the present invention includes a solar cell, a power conditioner having an inverter, wiring electrically connecting the solar cell and the power conditioner, a power supply unit capable of outputting a current to the wiring, a monitoring unit electrically connected to the power supply unit and configured to monitor the connection state of the wiring using the current when the wiring is in a conductive state by a switching unit capable of switching between a conductive state in which the wiring is electrically connected and a non-conductive state in which the wiring is not electrically connected, and a control unit that switches to the conductive state by the switching unit within a predetermined period of time including sunset, and causes the power supply unit to output the current to the wiring continuously or intermittently.

[0012] In this monitoring system, during a predetermined time period including sunset, in other words during a time period when theft of the wiring is likely to occur (for example, around sunset or at night), the switching unit switches the wiring and the monitoring unit to a conductive state, and the control unit outputs a current from the power supply unit to the wiring. As a result, the monitoring unit can monitor the connection state of the wiring using the above-mentioned current, making it possible to easily monitor the wiring against theft. In addition, in this system, since the connection state of the wiring is monitored using the current flowing through the wiring, it is possible to monitor for disconnection of the wiring with high accuracy, and it is possible to increase the immediacy of grasping the case of theft if it occurs. In addition, since the control unit switches the wiring and the monitoring unit to a conductive state or a non-conductive state using the switching unit, the monitoring unit can monitor the wiring only during a time period when monitoring of the wiring is particularly necessary.

[0013] In addition, when the solar cell is composed of multiple solar cell modules, the following effect can be achieved. Specifically, it is possible to monitor for breaks in the wiring that collects the power output from the multiple solar cell modules and outputs it to the power conditioner, or in the wiring that is connected to each solar cell module. As a result, it is possible to increase the immediacy of identifying cases of theft of wiring and to highly reliably prevent the theft of wiring from being overlooked.

[0014] Another monitoring system of the present invention includes a solar cell, a power conditioner having an inverter, wiring electrically connecting the solar cell and the power conditioner, a power supply unit capable of outputting a current to the wiring, a monitoring unit electrically connected to the power supply unit and configured to monitor the connection state of the wiring using the current when the wiring is in a conductive state by a switching unit capable of switching between a conductive state in which the wiring is electrically connected and a non-conductive state in which the wiring is not electrically connected, and a control unit which, when the electromotive force of the solar cell falls below a predetermined threshold value, switches to the conductive state by the switching unit and causes the power supply unit to output the current to the wiring constantly or intermittently.

[0015] In this monitoring system, when the electromotive force of the solar cell falls below a predetermined threshold, in other words, by determining a change (more specifically, a decrease) in the electromotive force of the solar cell during a time period when wiring theft is likely to occur (for example, around sunset or at night), the switching unit can switch the wiring and monitoring unit to a conductive state and monitor the connection status of the wiring.

[0016] As a modification of each of the above-mentioned inventions, it is a preferred embodiment that the control unit outputs the current from the power supply unit to the wiring in a state where the current does not flow to the inverter. By adopting this modification, the current does not flow to the inverter, so that it is possible to highly reliably prevent malfunction or failure of the inverter caused by the current flowing from the power supply unit to the inverter. Effect of the Invention

[0017] According to the present invention, it is possible to realize a monitoring system and a monitoring method that facilitates monitoring for wiring theft and increases the immediacy with which a theft incident can be detected. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a diagram illustrating a non-conductive state of the monitoring system of the first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a conduction state of the monitoring system of the first embodiment. [Diagram 3] FIG. 13 is a diagram illustrating a monitoring system according to a second embodiment. [Figure 4] FIG. 13 is a diagram illustrating a monitoring system according to a third embodiment. [Diagram 5] FIG. 13 is a diagram illustrating a monitoring system according to a fourth embodiment. [Figure 6] FIG. 13 is a diagram illustrating a monitoring system according to a modified example of the fourth embodiment. [Figure 7] FIG. 13 is a diagram illustrating a monitoring system according to a fifth embodiment. [Figure 8] FIG. 13 is a diagram illustrating a monitoring system according to a modified example of the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this description, common parts are given common reference symbols throughout the drawings unless otherwise specified. In addition, in the drawings, the elements of each embodiment are not necessarily shown to scale. In addition, some symbols may be omitted in order to make each drawing easier to see.

[0020] [Surveillance system] <First embodiment> Fig. 1 is a diagram showing a non-conductive state of the monitoring system 100 of this embodiment, and Fig. 2 is a diagram showing a conductive state of the monitoring system 100 of this embodiment.

[0021] As shown in FIG. 1, the monitoring system 100 of this embodiment includes a solar cell 2 installed in a location where it can receive sunlight, such as on the ground (not limited to flat ground but including ground in special topography such as mountainous areas), on the roof of a building, or on the roof of a house, a power conditioner 3 including an inverter 3a that converts DC power generated by the solar cell 2 into AC power, and wiring 4 that electrically connects the solar cell 2 and the power conditioner 3.

[0022] The solar cell 2 is typically composed of multiple solar cell modules. Each solar cell module includes a solar cell unit in which multiple solar cells that generate electricity through the photoelectric effect are electrically connected in series by conductors, and a base that fixes and supports the solar cell unit. Each solar cell module is provided with a positive connector and a negative connector that output the generated power.

[0023] The wiring 4 is a uniaxially extending conductor coated with an insulating layer and covered so that the surface of the insulating layer is not exposed. The materials constituting the conductor, insulating layer, and cover are appropriately changed based on the environment in which the solar cell 2 is placed and the power generation capacity of the solar cell 2, and in this embodiment, a copper wire is used for the conductor.

[0024] As shown in Figures 1 and 2, the wiring 4 connecting the solar cell 2 and the power conditioner 3 includes an output circuit 5 connecting the solar cell 2 and the power conditioner 3, and a monitoring circuit 6 branching off from the output circuit 5 for monitoring the wiring 4.

[0025] The output circuit 5 inputs the DC power generated by the solar cell 2 to the power conditioner 3. An example of the output circuit 5 includes an output positive wire 5A and an output negative wire 5B. The output positive wire 5A is connected to the positive connector of each solar cell module constituting the solar cell 2, and is also connected to the positive connector of the inverter 3a. The output negative wire 5B is connected to the negative connector of each solar cell module constituting the solar cell 2, and is also connected to the negative connector of the inverter 3a.

[0026] The monitoring circuit 6 is for monitoring a break in the wiring 4. The monitoring circuit 6 includes a monitoring positive line 6A branching off from the output positive line 5A, and a monitoring negative line 6B branching off from the output negative line 5B. An example of the monitoring circuit 6 includes a power supply unit 7, a monitoring unit 8, a switching unit 9, and a control unit 10. More specifically, the monitoring circuit 6 can be electrically connected to the power supply unit 7, the monitoring unit 8, and the control unit 10 by operating the switching unit 9, which will be described later.

[0027] The power supply unit 7 is a power supply that can pass a current from the wiring 4 to which the monitoring circuit 6 belongs to to the wiring 4 to which the output circuit 5 belongs by operating the switching unit 9 described later. In this embodiment, the positive electrode is connected to the monitoring positive line 6A, and the negative electrode is connected to the monitoring negative line 6B. With this configuration, the current output from the power supply unit 7 flows in the forward direction or the reverse direction to the current input from the solar cell 2 to the power conditioner 3. In this embodiment, for convenience of explanation, the current output from the power supply unit 7 to the wiring 4 is described as a "monitoring current", and the current input from the solar cell 2 to the power conditioner 3 is described as an "output current". The current value of the "monitoring current" is sufficiently small compared to the current value of the "output current", and a typical current value is more than 0.1 mA and 100 mA or less.

[0028] The power supply unit 7 may be configured to output a monitoring current to the output circuit 5. Therefore, it is one possible embodiment to use an external power generation device as the power supply unit 7, or to use a storage battery that stores the power generated by the solar cell 2 as the power supply unit 7. An example of the power supply unit 7 may be one that constantly outputs a monitoring current to the wiring 4, or one that outputs it intermittently. When the power supply unit 7 constantly outputs a monitoring current, the connection state of the wiring 4 can be constantly monitored. In addition, although the monitoring circuit 6 includes the power supply unit 7 in this embodiment, the output circuit 5 may include the power supply unit 7.

[0029] The monitoring unit 8 can monitor the connection state of the wiring 4 by using a monitoring current output from the power supply unit 7 to the wiring 4 through the operation of the switching unit 9 described later. An example of the monitoring unit 8 is provided in the monitoring circuit 6 so as to be in parallel with the output circuit 5 with respect to the power supply unit 7. In this embodiment, an example of the monitoring unit 8 is a voltmeter. The monitoring unit 8 measures the voltage value of the monitoring circuit 6 and transmits the measurement value to the control unit 10 described later.

[0030] The switching unit 9 is capable of switching between a conductive state in which the wiring 4 and the monitoring unit 8 are electrically connected, and a non-conductive state in which the wiring 4 and the monitoring unit 8 are not electrically connected. One example of the switching unit 9 includes a monitoring side relay 12 provided in the monitoring circuit 6, and an output side relay 11 provided in the output circuit 5.

[0031] The monitoring relay 12 is provided on either or both of the monitoring positive wire 6A and the monitoring negative wire 6B of the monitoring circuit 6, and can electrically connect or disconnect the output circuit 5 and the monitoring circuit 6. An example of the monitoring relay 12 has the following configurations (a) to (c). (a) A switch 12a provided on a monitoring positive line 6A arranged between a branch point from the output circuit 5 to the monitoring circuit 6, the power supply unit 7, and the monitoring unit 8. (b) A switch 12b provided on the negative monitoring line 6B between the branch point of the output circuit 5 to the monitoring circuit 6, the power supply unit 7, and the monitoring unit 8. (c) A monitoring side operating unit 12c that operates the switch 12a and the switch 12b

[0032] The output side relay 11 is provided on each of the output positive line 5A and the output negative line 5B, and can electrically connect or disconnect the output circuit 5 and the power conditioner 3. An example of this output side relay 11 has the following configurations (d) to (f). (d) A switch 11a provided on the output positive line 5A between the branch point where the output circuit 5 branches into the monitoring circuit 6 and the power conditioner 3. (e) A switch 11b provided on the output negative line 5B between the branch point where the output circuit 5 branches into the monitoring circuit 6 and the power conditioner 3. (f) Output side actuator 11c that operates switch 11a and switch 11b

[0033] In this embodiment, the energized state in which the wiring 4 and the monitoring unit 8 are electrically connected refers to the state shown in Fig. 2. In other words, the energized state refers to a state in which the switching unit 9 closes the switches 12a and 12b of the monitoring relay 12 to electrically connect the output circuit 5 and the monitoring circuit 6, and opens the switches 11a and 11b of the output relay 11 to electrically disconnect the output circuit 5 and the power conditioner 3. Therefore, in the energized state, no monitoring current flows through the inverter 3a provided in the power conditioner 3. Therefore, it is possible to reliably prevent malfunction or failure of the inverter 3a caused by current flowing from the power supply unit 7 to the inverter 3a.

[0034] In this embodiment, the non-energized state in which the wiring 4 and the monitoring unit 8 are not electrically connected refers to the state shown in Fig. 1. In other words, the non-energized state refers to a state in which the switching unit 9 opens the switches 12a and 12b of the monitoring relay 12 to thereby electrically disconnect the output circuit 5 and the monitoring circuit 6, and closes the switches 11a and 11b of the output relay 11 to thereby electrically connect the output circuit 5 and the power conditioner 3.

[0035] When a predetermined condition is satisfied, the control unit 10 switches the wiring 4 and the monitoring unit 8 to an energized state in which they are electrically connected by the switching unit 9, and outputs a monitoring current from the power supply unit 7 to the wiring 4 constantly or intermittently. The control unit 10 may include a switching control unit 13, a power supply control unit 14, a monitoring control unit 15, a storage unit 16, and an alert control unit 17. The control unit 10 is configured, for example, by a CPU (Central Processing Unit), and realizes the above-mentioned functions by executing a program stored in the storage unit 16, which is represented by a known HDD (Hard Disk Drive) or SSD (Solid State Drive). In another embodiment, a part of the control unit 10 may be located in a remote location or on a cloud via a public communication line such as the Internet.

[0036] In this embodiment, the "predetermined condition" refers to a time condition, and refers to a predetermined period of time including sunset. A more specific example is the period from one hour before sunset to one hour after sunset. In other words, when the predetermined condition is satisfied, it can be said that it is a time period when the solar cell 2 does not generate power, for example, around sunset or at night, when the wiring 4 is likely to be stolen.

[0037] The above-mentioned "predetermined condition" in a narrower sense is from 30 minutes before sunset to 30 minutes after sunset, and the above-mentioned "predetermined condition" in the narrowest sense is from 15 minutes before sunset to 15 minutes after sunset. Reducing the time before sunset contributes to extending the time for solar power generation, and reducing the time after sunset can contribute to starting theft monitoring more quickly. On the other hand, when a solar cell (or a solar cell module) is installed in a terrain such as a mountainous area, the solar cell or the solar cell module will not substantially generate power significantly before sunset. In such a case, among the above-mentioned "predetermined conditions," a longer time before sunset can increase the accuracy or effectiveness of theft monitoring. Therefore, the "predetermined condition" can be appropriately set depending on the surrounding environment including the installation location of the solar cell (or the solar cell module) (for example, including the terrain such as flat land, mountainous area, and outside temperature).

[0038] For example, when a clock built into the CPU reaches a predetermined time period including sunset, the switching control unit 13 transmits a switching signal to the monitoring side operation unit 12c of the monitoring side relay 12 and the output side operation unit 11c of the output side relay 11, thereby controlling them to enter a conductive state as shown in FIG. 2.

[0039] The power supply control unit 14 also sends a power signal to the power supply unit 7 when, for example, a clock built into the CPU is within a predetermined time period including sunset, and outputs a monitoring current from the power supply unit 7 to the monitoring circuit 6 either continuously or intermittently.

[0040] The monitoring control unit 15 receives the measurement value transmitted from the monitoring unit 8, and if the measurement value exceeds a predetermined threshold value, it determines that the wiring 4 has been disconnected and that theft has occurred, and transmits a disconnection signal to the alert control unit 17.

[0041] The alert control unit 17 receives the disconnection signal from the monitoring control unit 15 and transmits an alert signal to an external notification device. This external notification device is a known notification device including, for example, an alarm device that emits an alarm sound, a light source that emits a warning light, or a means for transmitting information including e-mail or SNS (social networking service) via the Internet to a monitoring PC or the like that is located at a remote distance from the monitoring system 100.

[0042] [Monitoring method] In this embodiment, the monitoring system 100 can be used to monitor the wiring 4 as follows.

[0043] <Switching process> In this embodiment, at a predetermined time including sunset, the switching control unit 13 of the control unit 10 transmits a switching signal to the monitoring side operation unit 12c of the monitoring side relay 12 and the output side operation unit 11c of the output side relay 11. The switching unit 9 that receives the switching signal switches the monitoring side relay 12 to a powered state in which the wiring 4 and the monitoring unit 8 are electrically connected as shown in Fig. 2. As described above, it is a preferred embodiment that the switching unit 9 at this time switches the wiring 4 (output circuit 5) and the power conditioner 3 to a state electrically disconnected (the state shown in Fig. 2) by the output side relay 11.

[0044] <Output process> After the above-mentioned switching step, the power supply control unit 14 transmits a power supply signal to the power supply unit 7. Upon receiving the power supply signal, the power supply unit 7 outputs a monitoring current to the monitoring circuit 6 constantly or intermittently.

[0045] <Monitoring process> The monitoring current output to the monitoring circuit 6 in the output process flows through the output circuit 5, and then is input again to the monitoring circuit 6 via the solar cell 2. Here, the power supply unit 7 and the monitoring unit 8 are arranged in parallel. When the wiring 4 is broken in the output circuit 5, the voltage value provided in the monitoring unit 8 will vary sufficiently greatly from the voltage value of the power supply unit 7 described above. With this configuration, the monitoring unit 8 measures the voltage value and monitors the change in the voltage value, i.e., the connection state of the wiring 4. The voltage value measured by the monitoring unit 8 is transmitted to the monitoring control unit 15. When the voltage value exceeds a predetermined threshold value, the monitoring control unit 15 determines that the wiring 4 has been stolen and transmits a disconnection signal to the alert control unit 17. The alert control unit 17 receives the disconnection signal from the monitoring control unit 15 and transmits an alert signal to an external alarm device.

[0046] In the monitoring process of this embodiment, when the power supply unit 7 is constantly outputting a monitoring current, the monitoring unit 8 also performs constant monitoring, and when the power supply unit 7 is intermittently outputting a current, the monitoring unit 8 also performs intermittent monitoring.

[0047] In the monitoring system 100 of this embodiment, a power supply unit 7, a monitoring unit 8, a switching unit 9, and a control unit 10 are provided in a monitoring circuit 6, and the switching unit 9 switches to a power-on state in which the wiring 4 and the monitoring unit 8 are electrically connected within a predetermined period of time including sunset. In the power-on state, a monitoring current output from the power supply unit 7 flows from the monitoring circuit 6 to the output circuit 5, and the monitoring unit 8 measures the voltage value of the output circuit 5 connected in parallel. Here, if the wiring 4 is disconnected due to theft or vandalism, the voltage value fluctuates in the monitoring unit 8, thereby increasing the immediacy of detection of theft of the wiring 4 and enabling easy and accurate monitoring.

[0048] Furthermore, since the monitoring system 100 operates during specific times including sunset, in other words during times when thefts are more likely to occur, such as around sunset or at night, it can act as an effective deterrent against theft of the wiring 4.

[0049] In addition, when current is output from the power supply unit 7, the output side relay 11 prevents a monitoring current from flowing to the inverter 3a, thereby preventing a reverse current from flowing to the inverter 3a. This makes it possible to reliably prevent malfunction or failure of the inverter 3a due to current flowing from the power supply unit 7 to the inverter 3a.

[0050] In addition, if a break occurs in the wiring 4, an alert signal is sent from the alert control unit 17 to the external abandoned device. Therefore, the damage caused by the theft can be reduced by increasing the deterrent effect against theft through an alarm sound or a warning light in response to the alert signal, and if the time when the alert signal was issued can be identified, it can also be used to identify the thief.

[0051] <Second embodiment> 3 is a diagram showing a monitoring system 200 of the present embodiment. The monitoring system 200 of the present embodiment is the same as the monitoring system 100 of the first embodiment, except that the control unit 10 further includes a determination unit 18. Therefore, descriptions overlapping with those of the first embodiment may be omitted.

[0052] As shown in FIG. 3, the monitoring system 200 of this embodiment further includes a determination unit 18 that determines whether or not the control unit 10 satisfies a predetermined condition, which will be described later.

[0053] When the determination unit 18 receives a measurement value from a voltmeter or the like provided in the solar cell 2 as an example of the above-mentioned predetermined condition and determines that the measurement value is equal to or greater than a predetermined threshold, it transmits a determination signal to the switching control unit 13 and the power supply control unit 14. The "predetermined threshold" can be set appropriately depending on the surrounding environment including the installation location of the solar cell 2 (including, for example, the topography such as flat land, mountainous area, and the outside temperature, etc.). A typical example of a threshold setting in a general installation location excluding special topography such as mountainous areas is 12V or more and 120V or less.

[0054] When the switching control unit 13 receives the above-mentioned determination signal, it transmits a switching signal to the monitoring-side operating unit 12c of the monitoring-side relay 12 of the switching unit 9 and the output-side operating unit 11c of the output-side relay 11. As a result, the switches 12a, 12b, 11a, and 11b are operated, and the switching control unit 13 controls the switching unit 9 to be in the energized state described in the first embodiment.

[0055] Furthermore, when the power supply control unit 14 receives the above-mentioned determination signal, it transmits a power supply signal to the power supply unit 7. The power supply unit 7 outputs a monitoring current to the monitoring circuit 6 either constantly or intermittently.

[0056] [Monitoring method] In this embodiment, the wiring 4 can be monitored as follows using the monitoring system 200. Note that the output process and the monitoring process overlap with those described in the first embodiment, so only the switching process will be described here.

[0057] <Switching process> When the determination unit 18 receives the measured value of the electromotive force of the solar cell 2 and determines that the measured value is equal to or less than a predetermined threshold value, the determination unit 18 transmits the above-mentioned determination signal to the switching control unit 13 and the power supply control unit 14. The switching control unit 13, which has received the determination signal, switches the switching unit 9 so that the wiring 4 and the monitoring unit 8 are electrically connected to each other and a current is applied. Furthermore, the power supply control unit 14, which has received the determination signal, outputs a monitoring current to the monitoring circuit 6 via the power supply unit 7.

[0058] In the monitoring system 200 of this embodiment, the judgment unit 18 transmits a judgment signal to the switching control unit 13 and the power supply control unit 14 based on the electromotive force of the solar cell 2. Therefore, the monitoring system 200 of this embodiment can be operated, for example, even during the day when the electromotive force of the solar cell is low, thereby increasing the deterrent effect against theft and reducing the damage caused by theft.

[0059] <Third embodiment> 4 is a diagram showing a monitoring system 300 of the present embodiment. The monitoring system 300 of the present embodiment is the same as the monitoring system 100 of the first embodiment or the monitoring system 200 of the second embodiment, except that a backflow prevention diode 19 is provided instead of the output side relay 11 in the first embodiment. Therefore, descriptions overlapping with the first and second embodiments may be omitted.

[0060] As shown in FIG. 4, the monitoring system 300 of the present embodiment includes a backflow prevention diode 19 provided in the output positive line 5A disposed between the branch point of the output circuit 5 and the monitoring circuit 6 and the power conditioner 3.

[0061] The switching unit 9 includes only a monitoring-side relay 12, and in this embodiment, the output-side relay 11 provided in the monitoring system 100 of the first embodiment is not provided.

[0062] In the monitoring system 300 of this embodiment, a backflow prevention diode 19 is installed in the output circuit 5. Here, the direction in which the monitoring current flows is opposite to the direction in which the output current flows. Therefore, even if the output side relay 11 is not provided on the output circuit 5 side, the backflow prevention diode 19 prevents the monitoring current from flowing to the inverter 3a. As a result, it is possible to reliably prevent malfunction or failure of the inverter 3a due to a reverse current flowing through the inverter 3a.

[0063] <Fourth embodiment> 5 is a diagram showing a monitoring system 400 of the present embodiment. The monitoring system 400 of the present embodiment is the same as the monitoring system 100 of the first embodiment, the monitoring system 200 of the second embodiment, or the monitoring system 300 of the third embodiment, except that a current collecting unit 20 is newly provided, the wiring 4 includes a first wiring 21 and a second wiring 22, and the power supply unit 7, the monitoring unit 8, the switching unit (the first switching unit 30 or the second switching unit 40), and the control unit (the control unit 10 or the control unit 31) are provided on the first wiring 21 and the second wiring 22, respectively. Therefore, descriptions that overlap with the first embodiment, the second embodiment, and the third embodiment may be omitted.

[0064] 5, in a monitoring system 400 of this embodiment, a solar cell 2 is composed of a plurality of solar cell modules 2A, 2B, and 2C. The number of solar cell modules can be changed appropriately depending on the scale of the photovoltaic power generation system.

[0065] The wiring 4 includes a first wiring 21 for inputting the DC power output from each of the solar cell modules 2A, 2B, 2C to the power collecting unit 20, and a second wiring 22 for electrically connecting the power collecting unit 20 and the power conditioner 3 and inputting the power collected by the power collecting unit 20 to the power conditioner 3.

[0066] The first wiring 21 includes a first output circuit 24 (24A, 24B, 24C) that electrically connects each of the solar cell modules 2A, 2B, 2C to the switch 23a, and a first monitoring circuit 25 branching off from the first output circuit 24.

[0067] The first output circuit 24 (24A, 24B, 24C) inputs the DC power output from each of the solar cell modules 2A, 2B, 2C to the switch 23a. The wiring belonging to the first output circuit 24 (24A, 24B, 24C) is as shown in (g) to (i) below, respectively. (g) The first output circuit 24A includes a first output positive wire 26A connecting the positive connector of the solar cell module 2A and the positive terminal of the switch 23a, and a first output negative wire 27A connecting the negative connector of the solar cell module 2A and the negative terminal of the switch 23a. (h) The first output circuit 24B includes a first output positive wire 26B connecting the positive connector of the solar cell module 2B and the positive terminal of the switch 23a, and a first output negative wire 27B connecting the negative connector of the solar cell module 2B and the negative terminal of the switch 23a. (i) The first output circuit 24C includes a first output positive wire 26C connecting the positive connector of the solar cell module 2C and the positive terminal of the switch 23a, and a first output negative wire 27C connecting the negative connector of the solar cell module 2C and the negative terminal of the switch 23a.

[0068] The first monitoring circuit 25 is for monitoring the first wiring 21 (particularly the first output circuit 24) for disconnection, and includes the wirings shown in (j) to (l) below. (j) A first monitoring positive wire 28A branching off from the first output positive wire 26A and a first monitoring negative wire 29A branching off from the first output negative wire 27A (k) A first monitoring positive wire 28B branching off from the first output positive wire 26B and a first monitoring negative wire 29B branching off from the first output negative wire 27B (l) A first monitoring positive wire 28C branching off from the first output positive wire 26C and a first monitoring negative wire 29C branching off from the first output negative wire 27C

[0069] The first monitoring circuit 25 includes a power supply unit 7 capable of outputting a monitoring current to the first wiring 21, a monitoring unit 8 for monitoring the connection state of the first wiring 21 using the monitoring current, a first switching unit 30, and a control unit 31. Here, the power supply unit 7 and the monitoring unit 8 overlap with the contents explained in the first embodiment, so only the first switching unit 30 and the control unit 31 will be explained below.

[0070] The first switching unit 30 is switchable between a conductive state in which the first wiring 21 and the monitoring unit 8 are electrically connected and a non-conductive state in which the first wiring 21 and the monitoring unit 8 are not electrically connected. The first switching unit 30 is provided in the first monitoring circuit 25, and includes first monitoring side relays 32 provided in the first monitoring positive wire 28 and the first monitoring negative wire 29 of the first monitoring circuit 25, respectively.

[0071] The first monitoring relay 32 electrically connects or disconnects the first output circuit 24 and the first monitoring circuit 25. An example of the first monitoring relay 32 includes (m) to (o). (m) A switch 33a provided on the first monitor positive line 28 arranged between the branch point of the first output circuit 24 and the first monitor circuit 25 and the power supply unit 7 and the monitor unit 8. (n) A switch 33b provided on the first monitor negative line 29 arranged between the branch point of the first output circuit 24 and the first monitor circuit 25 and the power supply unit 7 and the monitor unit 8. (o) A first monitoring side operating unit 33c that operates the switch 33a and the switch 33b

[0072] The switch 33a has a terminal A provided on the first monitoring positive wire 28A, a terminal B provided on the first monitoring positive wire 28B, a terminal C provided on the first monitoring positive wire 28C, and a terminal D provided on the first monitoring positive wire 28 on the power supply unit 7 and monitoring unit 8 side.

[0073] The switch 33b has a terminal A provided on the first monitoring negative wire 29A, a terminal B provided on the first monitoring negative wire 29B, a terminal C provided on the first monitoring negative wire 29C, and a terminal D provided on the first monitoring negative wire 29 on the power supply unit 7 and monitoring unit 8 side.

[0074] Here, a description will be given of the energized state in this embodiment in which the first wiring 21 and the monitoring unit 8 are electrically connected. The energized state in this embodiment refers to the state shown in Fig. 5. That is, in the first switching unit 30, the terminals D of the switches 33a and 33b are connected to any of the terminals A, B, and C in the closed state (in Fig. 5, as an example, the terminals D of the switches 33a and 33b are connected to the corresponding terminals B in the closed state), and the first output circuit 24 and the first monitoring circuit 25 are electrically connected.

[0075] In addition, the non-energized state in which the first wiring 21 and the monitoring unit 8 are not electrically connected refers to a state in which, in the first switching unit 30, terminals D of the switches 33a and 33b are in an open state in which they are not connected to any of terminals A, B, or C, and the first output circuit 24 and the first monitoring circuit 25 are electrically disconnected.

[0076] When a predetermined condition is satisfied, the control unit 31 switches the first switching unit 30 to the conductive state and causes the power supply unit 7 to output a monitoring current to the first wiring 21. Here, the predetermined condition refers to the time condition described in the first embodiment, or the "predetermined threshold" condition that is appropriately set depending on the surrounding environment including the installation location of the solar cell 2 described in the second embodiment. In the present embodiment, the following description will be given using the conditions in the first embodiment.

[0077] The control unit 31 may include a first switching control unit 113, a power supply control unit 14, a monitoring control unit 15, a storage unit 16, and an alert control unit 17. The control unit 31 has a configuration similar to that of the control unit 10 described in the first embodiment. In addition, since the configurations of the power supply control unit 14, the monitoring control unit 15, the storage unit 16, and the alert control unit 17 also overlap with those of the first embodiment, their descriptions will be omitted, and only the first switching control unit 113 will be described below.

[0078] For example, when a clock built into the CPU is within a predetermined time period including sunset, the first switching control unit 113 transmits a switching signal to the first monitoring side operation unit 33c of the first monitoring side relay 32. The first monitoring side operation unit 33c switches the terminal connected to the terminal D of the switch 33a in the order of terminal A, terminal B, and terminal C at regular intervals or at irregular time intervals. Similarly, the switch 33b also switches the terminal connected to the terminal D in the order of terminal A, terminal B, and terminal C at regular intervals or at irregular time intervals while synchronizing with the switch 33a.

[0079] The power collecting unit 20 collects DC power output from each of the multiple solar cell modules 2A, 2B, and 2C, and inputs the collected power together into the power conditioner 3. The power collecting unit 20 is disposed between the first wiring 21 and the second wiring 22, and includes a switch 23a, a current collector 23b, and a backflow prevention diode 23c, and may be housed in, for example, a connection box.

[0080] The switch 23a switches between a connected state in which the solar cell modules 2A, 2B, 2C are electrically connected and a cut-off state in which they are not electrically connected. The switch 23a also includes the following switches 114 (p) to (r). (p) A switch 114a provided on the first output positive line 26A and the first output negative line 27A electrically connected to the solar cell module 2A. (q) Switch 114b provided on the first output positive line 26B and the first output negative line 27B electrically connected to the solar cell module 2B (r) A switch 114c provided on the first output positive line 26C and the first output negative line 27C electrically connected to the solar cell module 2C.

[0081] With the above-mentioned configuration, by switching the switch 114a, the first output circuit 24A can be opened or closed, so the switch 23a can switch the solar cell module 2A to a connected state or a cut-off state. Similarly, by switching the switch 114b, the first output circuit 24B can be opened or closed, so the switch 23a can switch the solar cell module 2B to a connected state or a cut-off state. By switching the switch 114c, the first output circuit 24C can be opened or closed, so the switch 23a can switch the solar cell module 2C to a connected state or a cut-off state.

[0082] In addition, the switches 114a, 114b, and 114c can be independently switched by an operating unit (not shown) that operates the switch 114a, an operating unit that operates the switch 114b, and an operating unit that operates the switch 114c, respectively. Therefore, the connected or disconnected states of the solar cell module 2A, the solar cell module 2B, and the solar cell module 2C can be individually switched.

[0083] The current collector 23b is electrically connected to the switch 23a, and collects DC power output from the solar cell modules 2A, 2B, and 2C that are connected by the switch 23a.

[0084] The reverse current prevention diode 23c is disposed between the switch 23a and the current collector 23b. The reverse current prevention diode 23c is provided in each of the first output positive wire 26A electrically connected to the solar cell module 2A, the first output positive wire 26B electrically connected to the solar cell module 2B, and the first output positive wire 26C electrically connected to the solar cell module 2C.

[0085] The second wiring 22 includes a second output circuit that electrically connects the power collecting unit 20 and the power conditioner 3, and a second monitoring circuit 35 branching off from the second output circuit .

[0086] The second output circuit 34 inputs the DC power output from each of the solar cell modules 2A, 2B, 2C collected at the power collecting unit 20 to the power conditioner 3. The second output circuit 34 includes a second output positive wire 36 connecting the positive terminal of the power collecting unit 20 and the positive connector of the inverter 3a, and a second output negative wire 37 connecting the negative terminal of the power collecting unit 20 and the negative connector of the inverter 3a.

[0087] The second monitoring circuit 35 is for monitoring a break in the second wiring 22 (particularly, the second output circuit 34), and includes a second monitoring positive wire 38 branching off from the second output positive wire 36, and a second monitoring negative wire 39 branching off from the second output negative wire 37.

[0088] The second monitoring circuit 35 includes a power supply unit 7, a monitoring unit 8, a second switching unit 40, and a control unit 10. The power supply unit 7 is capable of outputting a monitoring current to the second wiring 22. The monitoring unit 8 is for monitoring the connection state of the second wiring 22 using the monitoring current. The second switching unit 40 is capable of switching between a conductive state in which the second wiring 22 and the monitoring unit 8 are electrically connected and a non-conductive state in which the second wiring 22 and the monitoring unit 8 are not electrically connected. An example of the second switching unit 40 includes a second monitoring side relay 47 and a second output side relay 46. The second monitoring side relay 47 is provided on the second monitoring positive line 38 and the second monitoring negative line 39, respectively, and electrically connects or disconnects the second output circuit 34 and the second monitoring circuit 35. The second output side relay 46 is provided on the second output positive line 36 and the second output negative line 37, respectively, and electrically connects or disconnects the power collector 20 and the power conditioner 3. When a predetermined condition is satisfied, the control unit 10 switches the second switching unit 40 to a conductive state and outputs a monitoring current from the power supply unit 7 to the second wiring 22. The monitoring unit 8, the power supply unit 7, and the control unit 10 overlap with the contents described in the first embodiment, and the second switching unit 40, the second monitoring side relay 47 included in the second switching unit 40, and the second output side relay 46 are similar in configuration to the switching unit 9, the monitoring side relay 12, and the output side relay 11 described in the first embodiment, so that the description will be omitted here.

[0089] In this embodiment, a power supply unit 7, a monitoring unit 8, a switching unit (first switching unit 30 or second switching unit 40), and a control unit (control unit 10 or control unit 31) are provided for each of the first wiring 21 and the second wiring 22, so that it is possible to monitor for breaks in the first wiring 21 (particularly, the first output circuit 24) and the second wiring 22 (particularly, the second output circuit 34).

[0090] Further, the switch 33a and the switch 33b of the first monitoring relay 32 each include a terminal A, a terminal B, a terminal C, and a terminal D, and the first switching control unit 113 switches the terminal to be connected to the terminal D in the order of terminal A, terminal B, and terminal C at regular time intervals or at irregular time intervals. Therefore, a monitoring current is passed through each of the first output circuit 24A, the first output circuit 24B, and the first output circuit 24C included in the first wiring 21, and it is possible to individually monitor disconnections in each of the solar cell modules 2A, 2B, and 2C. As a result, it is possible to highly reliably prevent the theft of the first output circuit 24 (24A, 24B, and 24C) and the second output circuit 34, which are the respective wirings, from being overlooked.

[0091] In addition, a reverse current prevention diode 23c is provided in each of the first output positive wire 26A, the first output positive wire 26B, and the first output positive wire 26C, which are disposed between the switch 23a and the current collector 23b. Therefore, the first switching unit 30 can reliably prevent malfunction or failure of the inverter 3a caused by a reverse current flowing through the inverter 3a, without providing an output side relay.

[0092] Now, an example will be described in which, in a solar cell system that has already been installed, a first output circuit and a second output circuit are provided, and the monitoring system 400 of this embodiment is additionally installed.

[0093] In the above case, first, a connection box including a first monitoring circuit 25 provided with the current collecting unit 20, power supply unit 7, monitoring unit 8, first switching unit 30, and control unit 31 of this embodiment is externally attached to the first output circuit. In addition, a second monitoring circuit 35 provided with the power supply unit 7, monitoring unit 8, second switching unit 40, and control unit 10 is applied to the second output circuit. With this configuration, even an existing solar cell system can be fitted with the monitoring system 400 of this embodiment, thereby enhancing the deterrent effect against theft and reducing damage caused by theft.

[0094] <Modification of the fourth embodiment> As a variation of the fourth embodiment, a monitoring system 500 is described below.

[0095] 6 is a diagram showing a monitoring system 500 according to a modification of this embodiment. The monitoring system 500 according to this modification is preferably used in a case where a first output circuit α ​​and a second output circuit β are provided in an already installed solar cell system, and a junction box X having a built-in reverse current prevention diode is also installed.

[0096] 6, in the monitoring system 500 of this modification, a junction box X is installed, and first, a first monitoring circuit 25 provided with a power supply unit 7, a monitoring unit 8, a first switching unit 30, and a control unit 31 is externally attached to the first output circuit α. In addition, a second monitoring circuit 35 provided with a power supply unit 7, a monitoring unit 8, a second switching unit 40, and a control unit 10 is externally attached to the second output circuit β. This allows the monitoring system 500 of this modification to be implemented in an already installed solar cell system, thereby increasing the deterrent effect against theft and reducing damage caused by theft.

[0097] <Fifth embodiment> 7 is a diagram showing a monitoring system 600 of the present embodiment. The monitoring system 600 of the present embodiment is the same as the monitoring system 100 of the first embodiment, the monitoring system 200 of the second embodiment, and the monitoring system 400 of the fourth embodiment, except that the current collecting unit 41 includes a fuse 42b instead of a backflow prevention diode, and the first switching unit 43 includes a first output side relay 44 in addition to the first monitoring side relay 32. Therefore, descriptions that overlap with the above-mentioned embodiments may be omitted.

[0098] 7, in the monitoring system 600 of the present embodiment, the current collecting unit 41 includes a current collector 42a and a fuse 42b that is provided upstream of the current collector 42a in the output current direction and cuts off an overcurrent or the like to protect the power conditioner 3. The fuse 42b is provided in each of the first output positive wire 26A, the first output positive wire 26B, and the first output positive wire 26C.

[0099] The first switching unit 43 is switchable between a conductive state in which the first wiring 21 and the monitoring unit 8 are electrically connected and a non-conductive state in which the first wiring 21 and the monitoring unit 8 are not electrically connected, and is equipped with a first output side relay 44 in addition to the first monitoring side relay 32.

[0100] The first output relay 44 electrically connects or disconnects the first output circuit 24 and the power collecting unit 41. That is, the first output relay 44 serves as a switch that switches between a connected state in which each of the solar cell modules 2A, 2B, and 2C and the power collecting unit 41 is electrically connected and a cut-off state in which they are not electrically connected.

[0101] An example of the first output side relay 44 has the following configurations (s) to (v). (s) Switches 45A provided on the first output positive line 26A and the first output negative line 27A arranged between the branch point of the first monitoring circuit 25A and the first output circuit 24A and the current collector 42a. (t) Switches 45B provided on the first output positive line 26B and the first output negative line 27B arranged between the branch point of the first monitoring circuit 25B and the first output circuit 24B and the current collector 42a. (u) Switches 45C provided on the first output positive line 26C and the first output negative line 27C arranged between the branch point of the first monitoring circuit 25C and the first output circuit 24C and the current collector 42a (v) a first output side operating portion 45D that operates the switches 45A, 45B, and 45C;

[0102] Here, the energized state in which the first wiring 21 and the monitoring unit 8 are electrically connected in the fifth embodiment refers to the state shown in Fig. 7. That is, in the first monitoring side relay 32, the terminal D of the switch 33a and the switch 33b is connected to any one of the terminal A, terminal B, and terminal C (in Fig. 7, as an example, the terminal D of the switch 33a and the switch 33b is connected to the terminal B), and the first output circuit 24 and the first monitoring circuit 25 are electrically connected. In addition, in the first output side relay 44, all of the switch 45A, the switch 45B, and the switch 45C are opened, and the solar cell 2 and the power collecting unit 41 are not electrically connected.

[0103] The non-energized state in which the first wiring 21 and the monitoring unit 8 are not electrically connected refers to the following state: In other words, in the first monitoring relay 32, terminals D of the switches 33a and 33b are in an open state in which they are not connected to any of terminals A, B, or C, and the first output circuit 24 and the first monitoring circuit 25 are in an electrically non-connected state. Additionally, in the first output relay 44, switches 45A, 45B, and 45C are all in a closed state, and the solar cell 2 and the power collecting unit 41 are in an electrically connected state.

[0104] In the monitoring system 600 of this embodiment, even if the collector unit 41 is not provided with a backflow prevention diode, by further providing the first output side relay 44, it is possible to highly reliably prevent malfunction or failure of the inverter 3a caused by the monitoring current flowing back from the collector unit 41 to the power conditioner 3.

[0105] Now, an example will be described in which the monitoring system 600 of this embodiment is additionally attached to an already installed solar cell system that includes a first output circuit and a second output circuit.

[0106] In the above case, first, a connection box including a first monitoring circuit 25 provided with the current collecting unit 41, power supply unit 7, monitoring unit 8, first switching unit 43, and control unit 31 of this embodiment is externally attached to the first output circuit. In addition, a second monitoring circuit 35 provided with the power supply unit 7, monitoring unit 8, second switching unit 40, and control unit 10 is provided to the second output circuit. With this configuration, even an existing solar cell system can be fitted with the monitoring system 600 of this embodiment, thereby enhancing the deterrent effect against theft and reducing damage caused by theft.

[0107] <Modification of the fifth embodiment> As a variation of the fifth embodiment, a monitoring system 700 is described below.

[0108] 8 is a diagram showing a monitoring system 700 according to a modification of this embodiment. The monitoring system 700 according to this modification is preferably used in a case where a first output circuit α ​​and a second output circuit β are provided in an already installed solar cell system, and a junction box Y having a built-in fuse is also installed.

[0109] As shown in Fig. 8, in the monitoring system 700 of this modification, a first monitoring circuit 25 provided with a power supply unit 7, a monitoring unit 8, a first switching unit 43, and a control unit 31 is externally attached to a first output circuit α. In addition, a second monitoring circuit 35 provided with a power supply unit 7, a monitoring unit 8, a second switching unit 40, and a control unit 10 is externally attached to a second output circuit β. In this case, if an existing solar cell system is already provided with a switch, the first switching unit 43 may be configured to include only the first monitoring side relay 32. This allows the monitoring system 700 of this modification to be implemented in an already installed solar cell system, thereby increasing the deterrent effect against theft and reducing damage caused by theft.

[0110] The present invention is not limited to the above-described embodiment. For example, it is another aspect that can be adopted in which the backflow prevention diode of the third monitoring system is applied to the first monitoring system or the second monitoring system.

[0111] Furthermore, for example, when there are circumstances in which it is clear that a wiring is prone to theft or other damage, or when there are circumstances that involve the cost of installation, the fourth monitoring system, the fifth monitoring system, or variations thereof, may be configured to provide a power supply unit, monitoring unit, switching unit, and control unit in either the first wiring or the second wiring, and to monitor only either the first wiring or the second wiring.

[0112] The disclosure of each of the above-mentioned embodiments is described for the purpose of explaining the embodiments, and is not described for the purpose of limiting the present invention. In addition, modifications within the scope of the present invention, including other combinations of each embodiment, are also included in the scope of the claims. [Explanation of symbols]

[0113] 2. Solar Cells 2A, 2B, 2C Solar cell modules 3 Power conditioner 3a Inverter 4. Wiring 5 Output circuit 6 Monitoring circuit 5A, 26A, 26B, 26C Output positive wire 5B, 27A, 27B, 27C Output negative wire 6A monitoring positive wire 6B Negative wire for monitoring 7 Power supply section 8 Monitoring Department 9,30,40,43 Switching section 10,31 Control section 11 Output relay 11a, 11b, 12a, 12b, 33a, 33b, 45A, 45B, 45C, 114, 114a, 114b, 114c Switches 11c Output side actuator 12 Monitoring relay 12c, 33c Monitoring side operating part 13 Switching control section 113 First switching control unit 14 Power supply control unit 15 Monitoring and control section 16 Memory section 17 Alert control section 18 Judgment section 19,23c Reverse current prevention diode 20,41 Current collector 21 1st wiring 22 2nd wiring 23a Switch 23b,42a Current collector 24,24A,24B,24C 1st output circuit 25,25A,25B,25C 1st monitoring circuit 28, 28A, 28B, 28C 1st monitoring positive wire 29, 29A, 29B, 29C 1st monitor negative wire 32 First monitoring relay 34 Second output circuit 35 Second monitoring circuit 36 Positive wire for second output 37 Second output negative wire 38 Second monitoring positive wire 39 Second monitoring negative wire 42b Fuse 44 First output relay 45D First output side actuator 46 Second output relay 47 Second monitoring relay 100, 200, 300, 400, 500, 600, 700 Surveillance System

Claims

1. A solar cell; A power conditioner having an inverter; Wiring electrically connecting the solar cell and the power conditioner; A power supply unit capable of outputting a current to the wiring; a monitoring unit that is electrically connected to the power supply unit and monitors a connection state of the wiring using the current when the power supply unit is in a conductive state by a switching unit that is switchable between a conductive state in which the power supply unit is electrically connected to the wiring and a non-conductive state in which the power supply unit is not electrically connected to the wiring; and a control unit that switches the state to the conductive state by the switching unit within a predetermined time period including sunset and causes the current to be output from the power supply unit to the wiring constantly or intermittently. Surveillance system.

2. A solar cell; A power conditioner having an inverter; Wiring electrically connecting the solar cell and the power conditioner; A power supply unit capable of outputting a current to the wiring; a monitoring unit that is electrically connected to the power supply unit and monitors a connection state of the wiring using the current when the power supply unit is in a conductive state by a switching unit that is switchable between a conductive state in which the power supply unit is electrically connected to the wiring and a non-conductive state in which the power supply unit is not electrically connected to the wiring; and a control unit that switches the state to the conductive state by the switching unit when the electromotive force of the solar cell becomes equal to or lower than a predetermined threshold value, and causes the current to be output from the power supply unit to the wiring constantly or intermittently. Surveillance system.

3. The control unit causes the power supply unit to output the current to the wiring in a state in which the current does not flow through the inverter. The monitoring system according to claim 1 or 2.

4. The solar cell is composed of a plurality of solar cell modules, A power collecting unit that collects DC power output from each of the plurality of solar cell modules, collects the collected power, and inputs the collected power to the power conditioner, The wiring includes a first wiring that electrically connects each of the solar cell modules and the power collecting unit to input DC power output from each of the solar cell modules to the power collecting unit, and a second wiring that electrically connects the power collecting unit and the power conditioner to input the power collected by the power collecting unit to the power conditioner, The monitoring unit is provided on the second wiring. The monitoring system according to claim 1 or 2.

5. The solar cell is composed of a plurality of solar cell modules, A power collecting unit that collects DC power output from each of the plurality of solar cell modules, collects the collected power, and inputs the collected power to the power conditioner, The wiring includes a first wiring that electrically connects each of the solar cell modules and the power collecting unit to input DC power output from each of the solar cell modules to the power collecting unit, and a second wiring that electrically connects the power collecting unit and the power conditioner to input the power collected by the power collecting unit to the power conditioner, The monitoring unit is provided on the first wiring. The monitoring system according to claim 1 or 2.

6. a switching step in which a switching unit capable of switching between a conductive state in which the switching unit is electrically connected to a wiring electrically connecting a solar cell and a power conditioner including an inverter and a non-conductive state in which the switching unit is not electrically connected to the wiring is switched to the conductive state within a predetermined time period including sunset; an output step of outputting a current from a power supply unit to the wiring in the conductive state after the switching step; A monitoring step in which a monitoring unit electrically connected to the power supply unit constantly or intermittently monitors a connection state of the wiring using the current when the wiring is in the conductive state. Monitoring method.

7. a switching step in which a switching unit capable of switching between a conductive state in which the switching unit is electrically connected to a wiring electrically connecting a solar cell and a power conditioner having an inverter and a non-conductive state in which the switching unit is not electrically connected to the wiring is switched to the conductive state when an electromotive force of the solar cell becomes equal to or lower than a predetermined threshold; an output step of outputting a current from a power supply unit to the wiring in the conductive state after the switching step; A monitoring step in which a monitoring unit electrically connected to the power supply unit constantly or intermittently monitors a connection state of the wiring using the current when the wiring is in the conductive state. Monitoring method.

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