Method for determining ground resistance, ground resistance monitoring system and measuring device

Abstract

The invention relates to a method for determining ground resistance, a ground resistance monitoring system and a measuring device. A ground resistance monitoring system includes a plurality of measurement devices configured to measure ground resistance values and arrangeable at different locations within a target area and at least one gateway device. Each of the plurality of gateway devices is communicatively coupled with at least one further measurement device of the plurality of measurement devices, and at least one measurement device of the plurality of measurement devices is in direct communication with at least one gateway device, and at least one measuring device of the plurality of measuring devices indirectly communicates only with the at least one gateway device such that a mesh network of the coupled measuring devices is formed. A ground resistance monitoring system is configured to perform a method for determining a ground resistance in a target area. Furthermore, a measuring device for a ground resistance monitoring system is described.

Description

Technical Field

[0001] The invention relates to a method for determining a ground resistance in a target area, a ground resistance monitoring system and a measuring device for measuring a ground resistance value. Background Art

[0002] The lightning protection system of a structure (such as a building) typically has three main parts, namely the air termination system, the down conductor and the earth termination system. When lightning strikes the lightning protection system, the lightning current generated is conducted from the air termination system through the down conductor to the earth termination system and into the ground. The performance of the earth termination system is critical to ensure that the lightning current is effectively dissipated.

[0003] One determining factor for the effectiveness of a lightning protection system is the ground resistance at the point where the grounding system enters the ground or soil. The ground resistance undergoes changes over time, for example due to environmental influences such as rain or sunlight, and due to aging effects of the grounding system. Therefore, to assess the effectiveness of a lightning protection system over its lifetime, it is necessary to determine the ground resistance after predetermined time intervals.

[0004] If a large number of lightning protection systems distributed over a large area, such as in an industrial plant or facility, are to be monitored, the necessary measurement of the ground resistance is laborious and time-consuming.

[0005] A ground resistance detection system for supervising an oil field well site is known from CN 215 813 045 U. The system comprises a large number of ground resistance monitoring devices capable of measuring the ground resistance of an associated ground body. Each ground resistance monitoring device sends the obtained measurement value to an upper host via a common gateway, through which the operator can control the operation of the system. In this way, the operator does not need to operate each monitoring device one by one. However, all monitoring devices need to be able to communicate with the common gateway in order to communicate with the upper host, which limits the possible arrangement of the monitoring devices within the oil field and / or makes it necessary to use communication modules with high power consumption. Summary of the invention

[0006] It is an object of the present invention to provide a method for determining the ground resistance in a simple, flexible and automated manner. Furthermore, it is an object of the present invention to provide a ground resistance monitoring system which enables reliable long-term measurement of the ground resistance.

[0007] The object of the present invention is solved by a method for determining a ground resistance in a target area, the method comprising the following steps:

[0008] a) providing a ground resistance monitoring system having a plurality of measuring devices and at least one gateway device, the plurality of measuring devices being configured to measure ground resistance values ​​and being arranged at different locations within the target area, wherein each of the plurality of measuring devices is communicatively coupled with at least one other measuring device of the plurality of measuring devices, and wherein at least one measuring device of the plurality of measuring devices communicates directly with at least one gateway device, and at least one measuring device of the plurality of measuring devices communicates only indirectly with the at least one gateway device, so that a mesh network of coupled measuring devices is formed;

[0009] b) measuring, by each of the plurality of measuring devices, a ground resistance value at a predetermined time stored in a control module of the corresponding measuring device;

[0010] c) forwarding the measured ground resistance value to a gateway device;

[0011] d) forwarding, by the gateway device, the updated scheduled time to the plurality of measuring devices; and

[0012] e) Repeating steps b) to d) at least once, wherein the predetermined time is an updated predetermined time.

[0013] The invention is based on the idea of ​​providing a mesh network of multiple measuring devices to determine the ground resistance at multiple locations throughout a target area. At the same time, not every measuring device within the mesh network needs to have a direct communication link with the associated gateway, but other measuring devices within the mesh network can be used as relay stations for communicating with the gateway device. Thus, the measuring devices can be flexibly distributed throughout the target area, because not every measuring device needs to be able to communicate directly with the gateway device, but only needs to be able to communicate directly with at least one other measuring device.

[0014] The expression “indirect communication” here and hereinafter means that the respective devices in indirect communication are coupled via at least one further measuring device.

[0015] Furthermore, all measuring devices measure the ground resistance value at a predetermined time in a time-coordinated manner. This facilitates the evaluation of the obtained ground resistance value. To ensure that the further measurements are also performed in a time-coordinated manner, the predetermined time is updated after each measurement based on instructions received from at least one gateway device.

[0016] The communication between different measuring devices and between a measuring device and at least one gateway device is bidirectional, so that information can be forwarded from a measuring device to at least one gateway device and from at least one gateway device to a measuring device, respectively.

[0017] The connection between the measuring device and at least one gateway device can be implemented wired or wirelessly. For example, the measuring device can be connected to another measuring device and / or a gateway device via a radio frequency connection (e.g., via RF 868 MHz), a mobile connection (e.g., via GSM / GPRS), a local wireless network connection (e.g., based on LORA or NB-IOT protocols), or a cable-based connection (e.g., using an RS485 communication link).

[0018] Of course, it is also possible that some of the connections between the devices of the ground resistance monitoring network are wired, and some of the connections are wireless.

[0019] In particular, it is determined which measuring devices in the mesh network are coupled to which other measuring devices and which measuring devices are coupled to a given gateway device within the ground resistance monitoring system, so that the distance between the directly coupled devices is minimized. This increases the reliability of data transmission between the directly coupled devices. However, depending on the structures in the target area (e.g., buildings or walls), the connection structure can also be selected based on the strength of the direct connection between the directly connected devices rather than the local proximity. Typically, the corresponding connection is flexible so that direct and indirect connections can be changed if necessary.

[0020] Thus, the overall transmission path from a given measuring device to the associated gateway device may be realized via a relay-like communication path using at least one further measuring device.

[0021] In order to provide optimized time-synchronized ground resistance values, the predetermined time may be the same for all measuring devices of the ground resistance monitoring system.

[0022] The ground resistance monitoring system may further include a central computing device communicatively coupled to the at least one gateway device, wherein the measured ground resistance value is sent by the at least one gateway device to the central computing device. In this way, the obtained ground resistance value may be stored and / or analyzed in the central computing device, so that the computing power of the at least one gateway device may be simplified.

[0023] Furthermore, the central computing device may be a cloud-hosted system to allow users of the ground resistance monitoring system to easily access the central computing device, and thereby access the ground resistance values ​​received from the at least one gateway, via an internet or network-based connection.

[0024] In order to reduce the number of active communication links, the measured ground resistance value can be sent by at least one gateway device to the central computing device only when the at least one gateway device has received the measured ground resistance value from each of the plurality of measuring devices. In other words, a given gateway device can first collect the ground resistance value measured by each of the measuring devices associated with the gateway device before establishing a transmission connection with the central computing device and sending the collected measurement data. In this way, the energy consumption of the gateway device can be further reduced.

[0025] To reduce energy consumption of multiple measuring devices, the difference between the scheduled time and the updated scheduled time is flexible. For example, the difference between the scheduled time and the updated scheduled time can be 24 hours or longer. The difference between the scheduled time and the updated scheduled time is most preferably 24 hours. Therefore, the measuring device only needs to be active for a short duration every day (e.g., once a day) to measure the ground resistance, forward the measured ground resistance to at least one gateway device, and receive the updated scheduled time from the associated gateway device.

[0026] The difference between the scheduled time and the updated scheduled time can be user adaptive. For example, the user can set the difference via the central computing device, and then the user setting is sent from the central computing device to at least one gateway device, so that the at least one gateway device determines the updated scheduled time based on the user setting.

[0027] Preferably, when the updated scheduled time has been received, the measuring device forwards a confirmation message to at least one gateway device. This allows an assessment of whether the correct updated scheduled time has actually reached all measuring devices in the ground resistance monitoring system, so that a situation in which some or all of the measured ground resistance values ​​are missing from a set of measurements performed at the updated scheduled time can be avoided.

[0028] If the at least one gateway device does not receive a confirmation message for each of the associated measuring devices, the at least one gateway may resend the updated scheduled time to ensure that all measuring devices have received the updated scheduled time.

[0029] Preferably, at least one gateway device comprises a seismic sensor for detecting seismic activity in the target area. If the amplitude of the seismic activity detected by the seismic sensor is greater than an amplitude threshold stored in a memory of the gateway device, the at least one gateway device forwards an alarm signal to the plurality of measurement devices.

[0030] In response to receiving the alarm signal, the measuring device may stop measuring the ground resistance value until a restart signal is received from at least one gateway device. The restart signal may be forwarded by the gateway device after the amplitude of the seismic activity decreases below the amplitude threshold again and / or after a predetermined seismic delay time after seismic activity with an amplitude greater than the amplitude threshold has been detected.

[0031] Therefore, by providing at least one gateway device with a seismic sensor, measurements affected by seismic events in the target area can be avoided. In this way, the reliability of the ground resistance value obtained by the measuring device can be further increased even if the target area is located in an area with strong and / or frequent seismic activity.

[0032] It is particularly advantageous if possible changes over time of the ground resistance values ​​obtained by the measuring device at different times are analyzed, for example, by a central computing device, since errors caused by seismic activity can be avoided or at least minimized.

[0033] The object of the present invention is also solved by a ground resistance monitoring system, which includes a plurality of measuring devices and at least one gateway device, the measuring devices being configured to measure ground resistance values ​​and being arranged at different locations within a target area. Each of the plurality of gateway devices is communicatively coupled to at least one other measuring device among the plurality of measuring devices. At least one measuring device among the plurality of measuring devices communicates directly with at least one gateway device. At least one measuring device among the plurality of measuring devices communicates only indirectly with at least one gateway device, so that a mesh network of coupled measuring devices is formed. The ground resistance monitoring system is configured to perform the above method.

[0034] Therefore, the features and advantages of the method according to the invention also apply to the ground resistance monitoring system and vice versa.

[0035] Each of the measuring devices may comprise an internal energy storage and / or be connectable to an external power supply.Preferably, the measuring devices are supplied with energy exclusively by the internal energy storage.

[0036] If the measuring device is powered only by the internal energy storage, the capacity of the internal energy storage is preferably selected such that the measuring device can be expected to operate for at least one year without requiring replacement of the internal energy storage. This reduces the manual labor associated with maintaining the ground resistance monitoring system.

[0037] The number of measurement devices associated with a single gateway device may be limited to a predetermined number of groups. For example, the predetermined number of groups may be 128 or more, for example, 255 measurement devices. Limiting the number of measurement devices avoids communication conflicts between a given gateway device and the associated measurement devices, and limits the total distance between the associated devices so that the transmission time of information exchanged between the devices does not become too long. Furthermore, the gateway device may be designed to be simpler in its communication capabilities and therefore cheaper.

[0038] The gateway device may be connected to further components for determining the ground resistance in addition to the measuring device. For example, the further components may be additional sensor devices for obtaining measurement data in addition to the ground resistance, such as temperature, humidity and / or pH value.

[0039] The measuring device may also include additional sensor elements for obtaining measurement data other than the ground resistance (eg temperature, humidity and / or pH value), which measurement data may be forwarded to the gateway device together with the ground resistance value.

[0040] To protect the measuring device from environmental influences, the measuring device may comprise a waterproof housing.

[0041] The measuring device may be free of a user interface. In other words, a user of the ground resistance monitoring system may not have access to the measured ground resistance value directly at the measuring device. Alternatively, the measured ground resistance value may only be evaluated in at least one gateway device and / or a central computing device. Thus, the measuring device does not need to provide an acoustic and / or graphical output to the user. In this way, the energy consumption of the measuring device is further reduced, so that it is less often necessary to replace the internal energy storage and / or the capacity of the internal energy storage can be reduced.

[0042] In order to ensure that the mesh network of measuring devices can always contact at least one gateway device, at least one gateway device of the ground resistance monitoring system can be connected to an external power supply. Thus, even in the case where the internal energy storage of all gateway devices of the ground resistance monitoring system is exhausted and the corresponding gateway device can no longer be powered, each measuring device can at least contact the gateway device powered by the external power device via the mesh network of measuring devices. In this case, this is the case even if a longer relay path via an additional measuring device must be selected to forward and receive data.

[0043] In a similar manner, if a plurality of gateway devices exist in the ground resistance measurement system, even in the event of a failure of an independent gateway device, the measuring device can forward the measured ground resistance value to another gateway device among the gateway devices by changing the relay path used.

[0044] The object of the present invention is also solved by a measuring device for measuring a grounding resistance value used in the grounding resistance monitoring system as described above.

[0045] The features and advantages of the ground resistance monitoring system according to the present invention also apply to the measuring device, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Other advantages and features of the present invention will become more apparent from the following description of preferred embodiments of the present invention and the accompanying drawings.

[0047] - Figure 1 shows a schematic diagram of a ground resistance monitoring system according to the invention having a plurality of measuring devices according to the invention, and

[0048] - Figure 2 The method for using the present invention is shown Figure 1 A block diagram of a method of determining ground resistance in a target area of ​​a ground resistance monitoring system. DETAILED DESCRIPTION

[0049] Figure 1 A schematic diagram of a ground resistance monitoring system 10 is shown that includes a plurality of measuring devices 12 to 22 distributed throughout a target area 24 .

[0050] The target area 24 is an area to be monitored by the ground resistance monitoring system 10, for example a plant facility having one or more (not shown) plant structures such as buildings protected by a lightning protection system. At least one of the measuring devices 12 to 22 is associated with each plant structure.

[0051] Each of the measuring devices 12 to 22 includes a ground resistance sensor 26 capable of measuring a ground resistance value at an installation location of the corresponding measuring device 12 to 22 .

[0052] Furthermore, each of the measuring devices 12 to 22 has a control module 28 , an internal energy storage 30 and a communication module 32 .

[0053] The control module 28 controls the operation of the respective measuring devices 12 to 22. In particular, the control module 28 is configured to switch the control module 28 between an active mode and a sleep mode, wherein in the sleep mode, some or all components of the measuring devices 12 to 22 except the control module 28 are disconnected from the internal energy storage 30. Thus, in the sleep mode, only the control module 28 and selected other components of the measuring devices 12 to 22 need to be powered by the internal energy storage 30, so that the overall energy consumption of the measuring devices 12 to 22 is reduced.

[0054] In the active mode, the measuring devices 12 to 22 may obtain ground resistance values ​​via the ground resistance sensor 26 and communicate with other devices in the ground resistance monitoring system 10 via the communication module 32 .

[0055] The predetermined time is stored in the control module 28 at which the control module 28 switches the measuring devices 12 to 22 from the sleep mode to the active mode and performs a ground resistance measurement, as will be described in more detail later.

[0056] The measuring devices 12 to 22 may also include one or more additional sensor elements for obtaining additional measurement values ​​in the active mode in addition to the ground resistance sensor 26. For example, the additional sensor elements are configured to measure pH, temperature and / or humidity values.

[0057] The measuring devices 12 to 22 do not include any user interface (such as a speaker or a display), so that a user of the ground system monitoring system 10 cannot directly access any data collected by the measuring devices 12 to 22 .

[0058] This further minimizes the energy consumption of the measuring devices 12 to 22 , so that a replacement of the internal energy storage device 30 can be avoided as long as possible, in order to reduce the amount of maintenance required for reliable operation of the grounding system monitoring system 10 .

[0059] The ground system monitoring system 10 further includes two gateway devices 34 and 36 .

[0060] Each gateway device 34 and 36 includes a gateway control module 37 , an internal gateway energy storage 38 , a memory 39 , a gateway communication module 40 , and a seismic wave sensor 42 .

[0061] The gateway control module 37 is configured to operate other components of the gateway devices 34 , 36 .

[0062] The gateway device 34 is also operatively connected to an external power source 44, which is capable of supplying the gateway device 34 with power to make it operable. That is, the external power source 44 ensures the operation of the gateway device 34 even in the case where the internal gateway energy storage 38 of the gateway device 34 is completely discharged. In principle, the gateway device 34 can also not have an internal gateway energy storage 38 and rely solely on the power supply of the external power source 44. The external power source provides a voltage in the range of 9 V to 36 V, for example.

[0063] In contrast, the gateway device 36 includes only an internal gateway energy storage 38 but is not connected to an external power source. Therefore, although the operation of the gateway device 36 can only be ensured by the internal gateway energy storage 38, since it does not need to be connected to an external power source, the gateway device 36 can be more flexibly arranged in the target area 24.

[0064] One or all of the gateway devices 34 , 36 may also be arranged outside the target area 24 , as long as at least one of the measurement devices 12 to 22 can still establish a direct communication link with the corresponding gateway device 34 , 36 .

[0065] In the illustrated embodiment, two gateway devices 34 and 36 are used. However, the ground system monitoring system 10 may also have only a single gateway device, preferably the gateway device 34 connected to the external power source 44, or more than two gateway devices 34, 36.

[0066] In addition, the grounding system monitoring system 10 may include Figure 1 More or fewer measuring devices 12 to 22 are shown in FIG. The number of measuring devices 12 to 22 depends in particular on the size of the target area 24 and / or the number of plant structures within the target area 24 which are to be protected from lightning strikes and which should therefore be monitored with regard to ground resistance.

[0067] The measuring devices 12 to 22 are coupled to each other for bidirectional communication via corresponding communication modules 32, such as Figure 1 Indicated by the double arrows in .

[0068] However, not every measuring device 12 to 22 is directly coupled to every other measuring device 12 to 22. Instead, some of the measuring devices 12 to 22 are only indirectly coupled to each other, wherein at least one further measuring device may act in a repeater-like manner to enable communication between the indirectly coupled measuring devices.

[0069] For example, measurement device 12 is directly coupled to measurement devices 14 and 16 , and is only indirectly coupled to measurement devices 18 , 20 , and 22 .

[0070] Overall, the measuring devices 12 to 22 form a mesh network of measuring devices.

[0071] In addition, the measurement device 12 is directly coupled to the gateway device 34 for bidirectional communication, and the measurement device 22 is directly coupled to the gateway device 36 for bidirectional communication, as also shown. Figure 1 More specifically, the corresponding communication module 32 and the gateway communication module 40 are communicatively coupled.

[0072] In contrast, measuring devices 14 to 20 are only indirectly coupled to gateway devices 34 and 36 for bidirectional communication, wherein at least one further measuring device serves as a relay station.

[0073] Of course, the number of measuring devices 12 to 22 directly and indirectly coupled to the gateway devices 34, 36 may be different from the number in the illustrated embodiment. However, according to the present invention, at least one measuring device 12 to 22 is directly coupled to at least one of the gateway devices 34, 36, and at least one measuring device 12 to 22 is only indirectly coupled to the gateway devices 34, 36.

[0074] Furthermore, the measuring devices 12 to 18 are usually associated with the gateway device 34, while the measuring devices 20 and 22 are usually associated with the gateway device 36. Here, "usually associated" defines that the corresponding measuring device communicates with the associated gateway device preferentially, and if the associated gateway device cannot be contacted, communicates with other gateway devices only by using a changed relay path including another measuring device. Figure 1 This is indicated by the dot-dash double arrow between the measuring device 14 and the measuring devices 20 and 22 .

[0075] Thus, each of the gateway devices 34, 36 is responsible for an associated number of measurement devices. The maximum number of measurement devices associated with a single gateway device 34, 36 may be limited to a predetermined number of groups, for example, a maximum of 255 different measurement devices.

[0076] Within the target area 24, additional components may be disposed that are also communicatively coupled to the gateway devices 34 and / or 36. Figure 1 In the embodiment shown in FIG. 4 , an exemplary sensor device 45 configured to obtain measurement data other than ground resistance value (eg, temperature, humidity, and / or pH value) is shown. The sensor device 45 is coupled to the gateway device 34 in a bidirectional communication manner.

[0077] The ground resistance monitoring system 10 also includes a central computing device 46 , which in the illustrated embodiment includes a server unit 48 and a user interface 50 .

[0078] The server unit 48 (and thus the central computing device 46) is bidirectionally communicatively coupled with each of the gateway devices 34 and 36, such as Figure 1 Indicated by the double arrows in .

[0079] The server unit 48 is located outside the target area 24 and provides, for example, an Internet of Things environment (IoT environment) that is typically accessible via the Internet and / or a local area network structure (eg, through the user interface 50 ).

[0080] The operating mode of the ground system monitoring system 10 will be described below within the framework of a method for determining a ground resistance in a target area 24 .

[0081] First, the ground resistance monitoring system 10 as described above is provided, wherein the measuring devices 12 to 22 are arranged to be distributed throughout the target area 24 ( Figure 2 , step S1 in the above example.

[0082] For example, the measuring devices 12 to 22 are each connected to a main ground connection (not shown) of the plant structure associated with the respective measuring device 12 to 22 .

[0083] A predetermined time is stored in the control module 28 of each of the measuring devices 12 to 22 at which the first measurement of the ground resistance value at the location of the measuring device 12 to 22 is to be started.

[0084] The predetermined time may be set by a user of the ground resistance monitoring system 10 via the user interface 50 and then forwarded to each of the measuring devices 12 to 22 via the gateway devices 34, 36. Thus, each of the measuring devices 12 to 22 receives the same predetermined time.

[0085] To synchronize the operation of the measuring devices 12 to 22, the control module 28 of the measuring devices 12 to 22 may include a real-time clock (RTC). If further synchronization is necessary, the RTCs of all measuring devices 12 to 22 may be coordinated by a server unit 48 acting as an NTP server (Network Time Protocol server).

[0086] At a predetermined time, each of the plurality of measuring devices 12 to 22 measures a ground resistance value ( Figure 2 , step S2 in the above example).

[0087] To this end, the control module 28 switches the measuring devices 12 to 22 from their sleep mode to their active mode, so that the ground resistance value can be measured via the ground resistance sensor 26 .

[0088] The ground resistance value may be determined by any known method for determining ground resistance, such as the 3-pole method. Preferably, the measurement takes no longer than one minute to minimize the time the measuring devices 12 to 22 need to be in active mode.

[0089] The obtained measured ground resistance value is then forwarded to the gateway device 34, 36 ( Figure 2 , step S3 in the above process).

[0090] However, the communication path of a given measuring device 12 to 22 for forwarding the measured ground resistance value depends on its location within the mesh network of measuring devices 12 to 22 .

[0091] The measuring devices 12 and 22 are directly coupled to the gateway devices 34 and 36 , respectively, and thus the measured ground resistance values ​​may be sent directly to the corresponding gateway devices 34 and 36 .

[0092] In contrast, the measurement devices 14 - 20 are only indirectly coupled to either of the gateway devices 34 and 36 , and thus forward the measured ground resistance value to the associated gateway device 34 - 36 through the relay path.

[0093] For example, the measuring device 18 sends its measured ground resistance value to the measuring device 14, and the measuring device 14 in turn sends both the measured ground resistance value of the measuring device 14 and the measured ground resistance value of the measuring device 18 to the measuring device 12. Then, the measuring device 12 sends all the received measured ground resistance values ​​to the gateway device 34.

[0094] The relay path selected for any given measurement device 14 - 20 may be selected based on the proximity of the measurement devices 12 - 22 to each other, the signal strength of the communication links between the measurement devices 12 - 22 and / or the gateway devices 34 , 36 associated with the respective measurement devices 14 - 20 .

[0095] The selected relay path does not necessarily correspond to the total shortest distance between two given measuring devices 12 to 22. In other words, the total relay path can be longer than the shortest distance. For example, the measuring device 16 can use a relay path including the measuring devices 18, 14 and 12 instead of a relay path in which the measuring device 16 communicates directly with the measuring device 12. Due to the mesh structure of the mesh network, the ground resistance monitoring system 10 provides high flexibility in the communication and relay paths actually used to forward data.

[0096] At least one additional information can be forwarded together with the grounding measurement value by the respective measuring device 12 to 22. The additional information can include a measuring device identifier, a state of the internal energy storage 30, a timestamp and / or a relay path identifier.

[0097] The gateway devices 34 and 36 collect the measured ground resistance values ​​and send the measured ground resistance values ​​to the central computing device 46 .

[0098] Preferably, the gateway devices 34, 36 wait to send the measured ground resistance value until the gateway devices 34, 36 have received the measured ground resistance value of each of the measuring devices 12 to 22 associated with the corresponding gateway devices 34, 36. Therefore, the gateway devices 34, 36 only need to perform one data transmission to the central computing device 46, so that the energy consumption of the gateway devices 34 and 36 can be minimized.

[0099] If the measuring devices 12 to 22 and / or the sensor device 45 have collected any additional values ​​(such as additional sensor values), these are also preferably sent together with the measured ground resistance value by the gateway device 34 , 36 to the central computing unit 46 .

[0100] Then, the gateway devices 34 and 36 determine an updated scheduled time, which is the time when the next measurement of the ground resistance value should occur. The updated scheduled time is particularly determined so that the difference between the scheduled time and the updated scheduled time is 20 hours or more. For example, the updated scheduled time is selected so that the next measurement of the ground resistance value is performed 24 hours after the start of the current measurement.

[0101] In principle, an updated scheduled time can also be determined by the central computing device 46 and sent to the gateway devices 34 and 36 .

[0102] The updated scheduled time is then forwarded by the gateway devices 34, 36 to the plurality of measuring devices 12 to 22 ( Figure 2 , step S4 in the above process).

[0103] In particular, the updated scheduled time is distributed within the mesh network of the measuring devices 12 to 22 by using the same but opposite relay path that has been used to forward the measured ground resistance value to the gateway devices 34 and 36. However, different relay paths may also be used to distribute the updated scheduled time within the mesh network as long as the updated scheduled time can be forwarded to each measuring device 12 to 22.

[0104] Once the measuring devices 12 - 22 receive the updated scheduled times, the respective measuring devices 12 - 22 may forward a confirmation message to the associated gateway device 34 , 36 indicating the successful transmission of the updated scheduled times.

[0105] If the gateway device 34 , 36 does not receive a confirmation message from all associated measuring devices 12 to 22 within a defined waiting period, the gateway device 34 , 36 may forward the updated predetermined time again.

[0106] After the measuring devices 12 to 22 have received the updated predetermined time, the control module 28 can set the corresponding measuring device 12 to 22 back to sleep mode, in which only the control module 28 or only the control module 28 and a selected number of components are powered by the internal energy storage 30 to minimize the energy consumption of the measuring devices 12 to 22.

[0107] When the updated scheduled time is reached, the above steps are repeated, wherein the scheduled time is the updated scheduled time. Thus, additional ground resistance values ​​will be determined and forwarded, additional updated scheduled times will be determined, etc. In this way, the ground system monitoring system 10 regularly provides ground system values ​​in a highly automated manner.

[0108] Thus, the central computing device 46 collects and stores a history of ground resistance values ​​that may be reviewed by a user of the ground system monitoring system 10 .

[0109] Furthermore, the central computing device 46 may analyze the ground resistance values ​​to identify trends that allow conclusions to be drawn about the state of the target area 24 , in particular the plant structures within the target area 24 .

[0110] As previously mentioned, the gateway devices 34, 36 include seismic sensors 42. In the event of a seismic event in the target area 24, the ground resistance values ​​obtained by the measuring devices 12-22 may be distorted, which may negatively affect the long-term evaluation of the ground resistance values ​​stored in the central computing device 46.

[0111] Therefore, if the amplitude of the seismic activity detected by the seismic sensor 42 is greater than the amplitude threshold stored in the memory 39 of the gateway devices 34, 36, the gateway devices 34, 36 forward the alarm signal to multiple measuring devices 12 to 22, that is, forward it within the entire mesh network of measuring devices 12 to 22.

[0112] Additionally, an alarm signal may also be sent to the central computing device 46 to inform the user of the ground resistance monitoring system of the seismic event.

[0113] Upon receiving the alarm signal, the control module 28 keeps the measuring devices 12 to 22 in the sleep mode until a restart signal is received from the gateway devices 34, 36. Therefore, the measuring devices 12 to 22 will not measure the ground resistance value until a restart signal has been received.

[0114] An additional alarm signal may also be sent to a further device 45 which, upon receipt of the alarm signal, also stops measuring values ​​until a restart signal is received.

[0115] The restart signal is forwarded by the gateway device 34, 36 after the amplitude of the seismic activity has again dropped below the amplitude threshold and / or after a predetermined seismic delay time after seismic activity having an amplitude greater than the amplitude threshold has been detected.

[0116] If the restart signal is forwarded at a time point later than the current scheduled time stored in the measuring devices 12 to 22 , the updated scheduled time is forwarded by the gateway devices 34 and 36 together with the restart signal.

[0117] Thereby, the normal operation of the ground resistance monitoring system 10 can be restored.

[0118] In summary, the ground resistance monitoring system 10 according to the present invention provides a simple and reliable method for obtaining a ground resistance value. The ground resistance monitoring system can be operated in a highly automated manner and has low requirements regarding maintenance.

Claims

1. A method for determining ground resistance in a target area (24), the method comprising the following steps: a) providing a ground resistance monitoring system (10) having a plurality of measuring devices (12, 14, 16, 18, 20, 22) and at least one gateway device (36, 38), wherein the plurality of measuring devices are configured to measure ground resistance values ​​and are arranged at different locations within the target area (24), wherein each of the plurality of measuring devices (12, 14, 16, 18, 20, 22) is communicatively coupled to at least one other measuring device (12, 14, 16, 18, 20, 22) of the plurality of measuring devices (12, 14, 16, 18, 20, 22), and wherein at least one measuring device (12, 14, 16, 18, 20, 22) of the plurality of measuring devices (12, 14, 16, 18, 20, 22) communicates directly with at least one gateway device (34, 36), and at least one measuring device (12, 14, 16, 18, 20, 22) of the plurality of measuring devices (12, 14, 16, 18, 20, 22) communicates only indirectly with the at least one gateway device (34, 36), such that a mesh network of coupled measuring devices (12, 14, 16, 18, 20, 22) is formed; b) measuring, by each of the plurality of measuring devices (12, 14, 16, 18, 20, 22), a ground resistance value at a predetermined time stored in a control module (28) of the corresponding measuring device (12, 14, 16, 18, 20, 22); c) forwarding the measured ground resistance value to the gateway device (12, 14, 16, 18, 20, 22); d) forwarding the updated scheduled time to the plurality of measuring devices (12, 14, 16, 18, 20, 22) by the gateway device (12, 14, 16, 18, 20, 22); and e) Repeating steps b) to d) at least once, wherein the predetermined time is an updated predetermined time.

2. The method according to claim 1, wherein: The ground resistance monitoring system (10) further includes a central computing device (46) communicatively coupled to the at least one gateway device (34, 36), and wherein the measured ground resistance value is sent by the at least one gateway device (34, 36) to the central computing device (46).

3. The method according to claim 2, wherein: The measured ground resistance value is sent by the at least one gateway device (34, 36) to the central computing device (46) only when the at least one gateway device (34, 36) has received the measured ground resistance value from each of the plurality of measuring devices (12, 14, 16, 18, 20, 22).

4. A method according to any one of the preceding claims, wherein: The difference between the scheduled time and the updated scheduled time is 24 hours or more.

5. A method according to any one of the preceding claims, wherein: When the updated scheduled time has been received, the measuring device (12, 14, 16, 18, 20, 22) forwards a confirmation message to the at least one gateway device (34, 36).

6. A method according to any one of the preceding claims, wherein: The at least one gateway device (12, 14, 16, 18, 20, 22) includes a seismic wave sensor (42) for detecting seismic wave activity in the target area (24), and if the amplitude of the seismic wave activity detected by the seismic wave sensor (42) is greater than an amplitude threshold stored in a memory (39) of the gateway device (34, 36), the at least one gateway device (34, 36) forwards an alarm signal to the plurality of measurement devices (12, 14, 16, 18, 20, 22).

7. A ground resistance monitoring system (10), comprising A plurality of measuring devices (12, 14, 16, 18, 20, 22) and at least one gateway device (34, 36), wherein the plurality of measuring devices are configured to measure ground resistance values ​​and can be arranged at different locations within a target area (24), in, Each of the plurality of measuring devices (12, 14, 16, 18, 20, 22) is communicatively coupled with at least one other measuring device (12, 14, 16, 18, 20, 22) of the plurality of measuring devices (12, 14, 16, 18, 20, 22), and wherein at least one measuring device (12, 14, 16, 18, 20, 22) of the plurality of measuring devices (12, 14, 16, 18, 20, 22) directly communicates with at least one gateway device (34, 36), and at least one measuring device (12, 14, 16, 18, 20, 22) of the plurality of measuring devices (12, 14, 16, 18, 20, 22) only indirectly communicates with the at least one gateway device (34, 36), so that a mesh network of coupled measuring devices (12, 14, 16, 18, 20, 22) is formed; The ground resistance monitoring system (10) is configured to perform the method according to any one of the preceding claims.

8. The ground resistance monitoring system (10) according to claim 7, wherein: The measuring device (12, 14, 16, 18, 20, 22) has no user interface.

9. The ground resistance monitoring system (10) according to claim 7 or 8, wherein: The at least one gateway device (34, 36) of the ground resistance monitoring system (10) is connected to an external power source (44).

10. A measuring device (12, 14, 16, 18, 20, 22) for measuring a ground resistance value, used in a ground resistance monitoring system (10) according to any one of claims 6 to 9.

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