Monitoring device for cathode protection system and cathode protection system

Abstract

The invention relates to a monitoring device for a cathodic protection system and the cathodic protection system. A monitoring device (20) for a cathodic protection system (10) for a metal structure (12) includes a sensor module (22) configured to measure an electrical signal indicative of a DC signal and an AC signal of the cathodic protection system (10), a control module (56), and a communication module (60) operatively coupled to a central processing device (66) of the cathodic protection system (10). The control module (56) is configured to switch the monitoring device (20) between a sleep mode and an active mode. The monitoring device (20) is configured, in an active mode, to obtain an electrical signal, to apply a first filter to the signal to obtain at least one filtered signal, to convert the at least one filtered signal into at least one digital signal, a second filter is applied to obtain at least one filtered digital signal and the at least one filtered digital signal is forwarded to a central processing device (66). A cathodic protection system (10) is also described.

Description

Technical Field

[0001] The invention relates to a monitoring device for a cathodic protection system and a cathodic protection system having a plurality of monitoring devices. Background Art

[0002] Metal structures such as pipelines are susceptible to corrosion processes if they are exposed to an environment that brings them into contact with reactive substances such as water and oxygen. This is especially true if the metal structure is buried underground, as is common with pipelines.

[0003] In order to inhibit or at least delay the corrosion process, it is known to protect metal structures with a cathodic protection system that applies an external DC (direct current) voltage between the metal structure and the anode of the cathodic protection system placed near the metal structure. Thus, the cathodic protection system can be applied to counteract the corrosion current, thereby preventing or at least minimizing corrosion of the metal structure. The DC voltage and the cathodic protection current applied by the cathodic protection system need to be checked regularly to evaluate the performance of the cathodic protection system.

[0004] Another influence on the corrosion process of metal structures is the applied AC (alternating current) voltage, which comes from electromagnetic fields close to the metal structure, for example, the electromagnetic field of high-voltage transmission lines near the metal structure. Therefore, it is also necessary to determine any AC voltage and current generated in the metal structure to evaluate the corrosion behavior.

[0005] Conventionally, multiple test points are provided along the metal structure, which are manually checked by trained personnel with monitoring equipment according to a given maintenance schedule. However, this process is time-consuming and incurs high costs, especially in application scenarios where the metal structure is located in remote areas, which is often the case with pipelines.

[0006] From US2011 / 0238347 A1 a system for measuring values ​​associated with cathodic protection of a structure is known. The system comprises a plurality of test units, wherein each test unit comprises a voltmeter for measuring the voltage between a reference cell and the structure. The test units are communicatively coupled to one another in a daisy chain or mesh radio network configuration, such that the measured voltage is sent to and from the test units until the voltage reaches one of the test units which is configured to upload any received signal to a web server or host computer. Although such a system provides an automatic determination of the voltage associated with the cathodic protection, the test units used have a high power consumption due to the necessary data transfer within the daisy chain or mesh network. Therefore, personnel still have to regularly go to the location of the test units to exchange and / or recharge the internal energy storage device of the test station. In addition, the test station needs to perform multiple measurements to obtain the necessary measurement results, thus further increasing the energy consumption of the monitoring device based on the number of measurements. Summary of the invention

[0007] The object of the present invention is to provide a cathodic protection system which has low requirements for maintenance and energy consumption while providing highly accurate information about the status of the cathodic protection system. In addition, the object of the present invention is to provide a monitoring device which can be used in such a cathodic protection system.

[0008] The object of the present invention is solved by a monitoring device for a cathodic protection system of a metal structure, the monitoring device comprising: a sensor module connectable to the metal structure and configured to measure an electrical signal indicating a DC signal and an AC signal of the cathodic protection system; and a control module operably coupled to the sensor module, the control module being configured to process the signal obtained from the sensor module and switch the monitoring device between a sleep mode and an active mode. The monitoring device also comprises a communication module operably coupled to the control module for forwarding the signal received from the control module to a central processing device of the cathodic protection system. The monitoring device is configured to obtain the electrical signal from the sensor module and apply a first filter to the electrical signal using a filter circuit of the sensor module to obtain at least one filtered electrical signal when in the active mode. The monitoring device is also configured to convert the at least one filtered electrical signal into at least one digital signal by an analog-to-digital converter, transmit the at least one digital signal to the control module, and apply a second filter to the at least one digital signal by applying a filtering function in the control module to obtain at least one filtered signal when in the active mode. In addition, the monitoring device is also configured to forward the at least one filtered digital signal to the central processing device by the communication module when in the active mode.

[0009] The invention is based on the idea of ​​measuring an electrical signal indicative of a DC signal and an AC signal, such that both the DC signal and the AC signal can be measured simultaneously. In other words, the DC signal and the AC signal are analyzed simultaneously. Thus, the number of measurements that the monitoring device must make in order to obtain the necessary information for assessing the state of the cathodic protection system and the metal structure is minimized. The reduction in the number of measurements also reduces the energy consumption of the monitoring device, thereby extending the operating time of the monitoring device without manual intervention. Furthermore, the control device can switch the monitoring device between a sleep mode and an active mode, such that energy consumption can be minimized at any time when no measurements need to be made.

[0010] Furthermore, a two-step filtering process is used to improve the quality of measurements obtained by the monitoring device in active mode, wherein the first filter is a hardware-based filter and the second filter is a software-based filter.

[0011] The software-based filter may be a FIR filter (Finite Impulse Response filter). A FIR filter is particularly effective for suppressing noise in the at least one digital signal, so that the quality of the filtered digital signal is further improved.

[0012] Preferably, the metal structure is a pipe.

[0013] The term "DC signal" refers to a DC signal including both a DC voltage and a DC current. The term "AC signal" refers to an AC signal including both an AC voltage and an AC current.

[0014] The filter circuit is particularly configured to separate the DC signal and the AC signal when processing the electrical signal, so that a filtered DC signal and a filtered AC signal are obtained. Therefore, two pieces of information about the influence of DC and AC on the cathodic protection system and / or the metal structure can be obtained from a single electrical signal, while providing the possibility of processing the filtered DC signal and the filtered AC signal independently of each other.

[0015] Preferably, the filter circuit comprises a low-pass filter and a high-pass filter, so that only a defined frequency range has to be considered in the filtered electrical signal. This facilitates further processing of the electrical signal and improves the accuracy of the measurement results obtained.

[0016] The low pass filter is particularly configured to filter frequencies of 30 Hz or lower. Thus, the low pass filter particularly selects frequencies that may be associated with DC contributions in the electrical signal. In particular, these contributions are related to the cathodic protection voltage and the cathodic protection current provided by the cathodic protection system.

[0017] The high pass filter is in particular configured to filter frequencies above 30 Hz, for example frequencies in the range of 40 to 60 Hz. Thus, the high pass filter in particular selects frequencies that may be associated with AC contributions in the electrical signal, in particular AC contributions having a frequency equal to or close to a typical mains voltage, such as 50 Hz. Therefore, these AC contributions are in particular relevant to the influence of mains voltage lines located near metal structures.

[0018] In order to ensure particularly reliable communication between the monitoring device and the central processing device of the cathodic protection system, the communication module can be a LoRa communication module. Therefore, the monitoring device can be implemented in a LoRaWAN (Long Range Wide Area Network). In this way, the monitoring device does not need to be accessible in a mobile communication network / cellular network, so that problems with the availability of mobile communication networks based on GSM, LTE and / or 5G technology, for example, can be avoided, which is particularly advantageous when the metal structure is located in a remote area. In addition, the LoRa communication module has an integrated energy-saving capability, which further extends the time during which the monitoring device can operate without human intervention. Moreover, the LoRa communication module provides the possibility of point-to-point communication and can provide wireless communication over a distance of several kilometers, in particular over a distance of 10 km or more.

[0019] In order to expand a measurement range of the monitoring device, the sensor module may include a first shunt resistor and a second shunt resistor, wherein the first shunt resistor has a maximum operating current different from that of the second shunt resistor.

[0020] The measuring range of the monitoring device is in particular 1 μA to 500 mA.

[0021] The monitoring device may comprise a memory module for storing the filtered digital signal. That is, the filtered digital signal obtained in the active mode of the monitoring device may also be stored within the monitoring device itself.

[0022] In particular, if the transmission to the central processing device of the cathodic protection system fails, the monitoring device is configured to store the filtered digital signal in the memory unit. In this way, loss of measurement data can be avoided. The monitoring device can be configured to forward the filtered digital signal stored in the memory unit when the monitoring device next enters active mode and successful communication with the central processing device is possible again.

[0023] In order to further minimize the energy consumption of the monitoring device, in the sleep mode of the monitoring device, only the control module can be connected to the internal energy storage device of the monitoring device. That is, in the sleep mode of the monitoring device, only the control module needs to be powered on, so that the monitoring device can be switched from the sleep mode to the active mode by the control module. The further components of the monitoring device can thus be disconnected to avoid any energy consumption of these components in the sleep mode. This is particularly preferred because, in particular, the communication module is usually one of the largest contributors to the energy consumption of the monitoring device. However, during the active mode of the monitoring device, the availability of the monitoring device is still given within a short time window. Overall, the time during which the monitoring device can operate without human intervention can thus be particularly effectively increased.

[0024] The control module can be configured to switch the monitoring device from the sleep mode to the active mode after a predetermined time interval. That is, the time window in which the monitoring device is actually active can be precisely controlled. In particular, the predetermined interval is selected so that the monitoring device measures the electrical signal once a day.

[0025] The objects of the present invention are further solved by a cathodic protection system for protecting a metal structure, the cathodic protection system comprising: a cathodic rectifier electrically connected to the metal structure for applying a cathodic protection voltage between the metal structure and a reference electrode; a plurality of monitoring devices as described above connected to the metal structure; and one or more gateway devices, wherein each of the plurality of monitoring devices is communicatively coupled to at least one of the gateway devices. The cathodic protection system also comprises a central processing device communicatively coupled to the gateway device.

[0026] The features and advantages of monitoring equipment as described above also apply to cathodic protection systems and vice versa.

[0027] The cathodic protection system according to the present invention can operate for an extended period of time without human intervention, while obtaining information about the status of the cathodic protection system and / or the metal structure protected by the cathodic protection system in an automatic manner based on electrical signals obtained by each of a plurality of monitoring devices.

[0028] Preferably, each of the monitoring devices is directly coupled to one or more gateway devices. In other words, preferably, the plurality of monitoring devices and the one or more gateway devices form a star network architecture or, if there is more than one gateway device, a star-to-star network architecture. This greatly simplifies the overall network design of the devices that are part of the cathodic protection system. In addition, no additional communication links are required between the monitoring devices, which allows minimizing the time that the communication modules of the monitoring devices need to be active and the number of connections that the communication modules have to establish, thereby minimizing energy consumption.

[0029] In particular, each of the monitoring devices is directly coupled to one or more gateway devices via a local network protocol. Thus, the monitoring device does not need to communicate with the one or more gateway devices via a mobile communication network, so that a particularly reliable communication link can be established between the monitoring device and the one or more gateway devices. Preferably, the local network protocol is based on LoRa.

[0030] One or more gateway devices may be connected to the central processing device via a mobile communication network, for example, based on GSM, LTE and / or 5G technology. Thus, one or more gateway devices may provide a link between the local network formed between the monitoring device and the one or more gateway devices and the central processing device.

[0031] Preferably, a plurality of monitoring devices are configured to switch between sleep mode and active mode simultaneously. Thus, there is a defined time window during which the communication link between the monitoring device and the one or more gateway devices needs to be active, while at all other times the communication link may be inactive to reduce energy consumption of the monitoring device and the one or more gateway devices.

[0032] In order to coordinate the time when the monitoring devices switch between the sleep mode and the active mode, the central processing device can be configured to act as an NTP server (i.e., a network-time-protocol server). During the active mode of the monitoring device, the central processing device can forward the NTP information to the multiple monitoring devices, so that the control module of each of the monitoring devices can adjust the internal real-time clock (RTC) based on the NTP information. Therefore, there is no need to use more complex and / or more energy-consuming measures for time coordination between monitoring devices, such as GPS-based time coordination.

[0033] In addition, the one or more gateway devices may only act as a relay station between the monitoring device and the central processing device. Therefore, the design of the one or more gateway devices may be simplified, thereby reducing the overall cost of the cathodic protection system. In addition, the effort to configure the one or more gateway devices is minimized, thereby eliminating or at least reducing the need for manual intervention of personnel at the location of the one or more gateway devices to set up network operation of the one or more gateway devices.

[0034] To provide redundant communication pathways, the cathodic protection system may include more than one gateway device, and each of the monitoring devices may be connected to several of the gateway devices. Thus, if the default gateway device cannot be contacted, the monitoring device may be configured to forward any data to be sent to the central processing device via another gateway device. In other words, the monitoring device may be configured to automatically reroute data transmissions to the central processing device.

[0035] The monitoring device may also be connected to several gateway devices and always send any data to be forwarded to the central processing device to all several gateway devices. Although this leads to increased effort in sending data multiple times, there is no need to check whether a given gateway device can actually be contacted.

[0036] The data forwarded by each of the monitoring devices may include, in addition to the at least one filtered digital signal, additional information, such as an identifier, status information, a signal strength indicator, a battery health indicator, and / or a ping counter.

[0037] The central processing device may store the data received from the monitoring device in the server memory unit. Preferably, the central processing device is configured to construct a historical data set based on the data stored in the server memory unit and analyze the historical data set to obtain at least one information about the status of the cathodic protection system and the metal structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Additional advantages and features of the present invention will become apparent from the following description of preferred embodiments and the accompanying drawings, which description should not be construed as limiting. In the drawings:

[0039] - Figure 1 A schematic diagram showing a cathodic protection system according to the present invention, the system having a plurality of monitoring devices according to the present invention; and

[0040] - Figure 2 Shows Figure 1 A selected portion of a circuit arrangement of a monitoring device. DETAILED DESCRIPTION

[0041] Figure 1 A cathodic protection system 10 for protecting a metal structure 12 from corrosion is shown in accordance with the present invention.

[0042] In the embodiment shown, the metal structure 12 is a metal pipe buried underground. The pipe is therefore exposed to water, oxygen and other environmental influences in the soil, so there is a risk that the pipe will be damaged over time due to corrosion. The pipe is made of stainless steel, for example. Of course, the metal structure 12 can also be made of different materials.

[0043] The cathodic protection system 10 is used to prevent or at least minimize the effects of corrosion of the metal structure 12 and to provide monitoring information that allows the current status of the cathodic protection system 10 and the metal structure 12 to be estimated.

[0044] Cathodic protection system 10 includes two cathode rectifiers 14, each of which is electrically connected to metal structure 12 by a rectifier switch 16 and to reference electrode 18. In addition, each of cathode rectifiers 14 is electrically connected to a power source (not shown) that powers the corresponding cathode rectifier 14.

[0045] The cathode rectifier 14 is configured to apply a cathode protection potential V between the metal structure 12 and the reference electrode 18. 保护 ,like Figure 1 Indicated by the dotted double arrows in the figure. 保护 Associated with this is the cathodic protection current I 保护 . Cathodic protection potential V 保护Corresponding to a direct current (DC) voltage with a negative sign, it should be greater than any DC corrosion potential expected for the metal structure 12. In general, the cathodic protection potential V 保护 Should be less than -850mV.

[0046] Of course, the number of cathode rectifiers 14 can be as large as Figure 1 For example, the cathodic protection system 10 may include only a single cathode rectifier 14 or more than two cathode rectifiers 14. In general, the number of cathode rectifiers 14 will depend on the overall size of the metal structure 12 and should be selected so as to ensure that there is sufficient cathodic protection potential V across the entire metal structure 12. 保护 .

[0047] The cathodic protection system 10 also includes a plurality of monitoring devices 20 distributed along the length of the metal structure 12 , the monitoring devices 20 being electrically connected to the metal structure 12 .

[0048] Each of the monitoring devices 20 has a sensor module 22 electrically connected to the metal structure 12 , and a measuring electrode 24 , with which the sensor module 22 can obtain an electrical signal indicating a DC signal and an AC signal of the cathodic protection system 10 .

[0049] The DC signal is derived in particular from the DC potential V applied by the cathode rectifier 14. 保护 However, the DC signal may be affected by additional corrosion potentials coupled into the metal structure 12 and external DC potentials, such as those caused by industrial equipment near the metal structure 12 .

[0050] The AC signal originates in particular from the AC potential of the main connecting line in the vicinity of the metal structure 12 .

[0051] Both the DC signal and the AC signal provide an indication of potential corrosion effects on the metal structure 12 , such that information about the current state of the metal structure 12 may be obtained by evaluating the DC signal and the AC signal.

[0052] The potential associated with the electrical signal is indicated by a dashed double arrow and is Figure 1 Indicated as V 信 Number.

[0053] The sensor module 22 further comprises a filtering circuit 26 adapted to apply a first filter to the electrical signal obtained by the sensor module 22 to obtain at least one filtered electrical signal.

[0054] Figure 2 Selected portions of the circuit arrangement of sensor module 22 including filter circuit 26 are shown.

[0055] The electrical signal obtained by the sensor module 22 is fed into the circuit arrangement at the input 27. As explained before, the electrical signal may have contributions from both the DC signal and the AC signal. Preferably, the contributions of both the DC signal and the AC signal to the electrical signal are accessible via the sensor module 22.

[0056] To this end, in the illustrated embodiment, the filter circuit 26 includes a high-pass filter 28 and a low-pass filter 30 .

[0057] The high-pass filter 28 is composed of three high-pass filter elements 31, 32, and 34 connected in series, wherein the capacity of the capacitor associated with each of the high-pass filter elements 31, 32, and 34 decreases from the input side of the high-pass filter 28 to the output side of the high-pass filter 28, and the resistance of the resistor associated with the corresponding high-pass filter elements 31, 32, and 34 increases. That is, the capacity of the capacitor C79 is larger than the capacity of the capacitor C81, and the capacity of the capacitor C81 is larger than the capacity of the capacitor C83, while the resistance of the resistor R10 is lower than the resistance of the resistor R11, and the resistance of the resistor R11 is lower than the resistance of the resistor R12.

[0058] After passing through the high-pass filter 28 , a filtered electrical signal, ie a filtered AC signal, is obtained at a high-pass output 36 .

[0059] The high pass filter 28 is in particular configured such that the high pass filter 28 filters frequencies above 30 Hz, for example, frequencies in the range from 40 to 60 Hz. In this way, in the filtered AC signal, the contribution of the AC part of the electrical signal close to the general mains voltage, typically 50 Hz, can be clearly seen.

[0060] The low-pass filter 30 is composed of three low-pass filter elements 38, 40, and 42 connected in series, wherein the resistance of the resistor associated with each of the low-pass filter elements 38, 40, and 42 generally increases from the input side of the low-pass filter 30 to the output side of the low-pass filter 30, and the capacitance of the capacitor associated with the respective low-pass filter elements 38, 40, and 42 increases. That is, the resistance of the resistor R21 is lower than the resistance of the resistor R25, and the capacitance of the capacitor C84 is lower than the capacitance of the capacitor C85 and the capacitance of the capacitor C85 is lower than the capacitance of the capacitor C86.

[0061] After passing through the low-pass filter 30 , a filtered electrical signal, ie a filtered DC signal, is obtained at a low-pass output terminal 44 .

[0062] The low pass filter 30 is in particular configured such that the low pass filter 30 filters frequencies of 30 Hz or lower. In this way, the contribution to the DC part of the electrical signal can be clearly seen in the filtered DC signal.

[0063] As from Figure 2 It becomes clear that both the filtered AC signal and the filtered DC signal can be obtained simultaneously by a single measurement of the electrical signal by the sensor module 22 and providing the electrical signal at the input 27. Thus, the number of separate measurements that the monitoring device 20 must perform can be reduced without losing information.

[0064] In principle, however, it is also possible to be interested in only selected parts of the electrical signal, so that the filter circuit 26 can be designed such that only a filtered DC signal or a filtered AC signal is obtained.

[0065] The filtered DC signal and the filtered AC signal each include corresponding voltage and current information of the corresponding signal. That is, the sensor module 22 provides DC voltage, DC current, AC voltage and AC current.

[0066] In order to increase the available measurement range of the monitoring device, the sensor module 22 also includes a first shunt resistor 46 and a second shunt resistor 48. Figure 2 The first shunt resistor 46 and the second shunt resistor 48 have different maximum operating currents.

[0067] When the current associated with the electrical signal from input terminal 27 exceeds the maximum operating current of the shunt having a lower maximum operating current, it can be determined which of the first shunt resistor 46 and the second shunt resistor 48 is active based on the shunt switch circuit 50 providing a shunt switch input signal from the shunt switch input terminal 53 to the shunt controller 52.

[0068] For example, if the first shunt resistor 46 is configured to handle currents in the range from 1 μA to a maximum operating current of 500 μA and the second shunt resistor 48 is configured to handle currents in the range from 500 μA to a maximum operating current of 500 mA, then when the current associated with the electrical signal exceeds 500 μA, an overall operating range from 1 μA to 500 mA can be achieved by switching the active shunt resistor from the first shunt resistor 46 to the second shunt resistor 48.

[0069] Back to Figure 1 Each of the sensor modules 22 further includes an analog-to-digital converter 54 that converts the filtered electrical signal from the filter circuit 26 into at least one digital signal. Specifically, the analog-to-digital converter 54 converts the filtered AC signal into a digital AC signal and converts the filtered DC signal into a digital DC signal.

[0070] Each of the monitoring devices 20 also includes a control module 56 that is operably coupled to the sensor module 22. Thus, the sensor module 22 is configured to transmit the at least one filtered signal to the control module 56 so that the control module 56 can process the at least one filtered signal.

[0071] The control module 56 applies a second filter to the at least one digital signal by applying a filter function to obtain at least one filtered digital signal. More precisely, if the control module 56 receives a digital AC signal and a digital DC signal from the sensor module 22, the second filter is applied to each of the digital AC signal and the digital DC signal so that a filtered digital AC signal and a filtered digital DC signal are obtained.

[0072] The second filter is in particular a FIR filter, which is used to achieve effective noise reduction.

[0073] The control module 56 is also operably connected to the memory module 58 such that the control module 56 can access data stored in the control module 56 and can store at least one filtered signal in the memory module 58 when necessary.

[0074] Each of the monitoring devices 20 also includes a communication module 60 operatively coupled to the control module 56 , which allows the monitoring device 20 to communicate with other devices of the cathodic protection system 10 .

[0075] The communication module 60 is a LoRa communication module, so that the monitoring device 20 can be used as a device within a LoRaWAN (Long Range Wide Area Network). In this way, the communication of the monitoring device 20 is independent of the availability of a mobile communication network at the location where the respective monitoring device 20 is located.

[0076] However, it is clear that in application scenarios where a stable mobile communication network is provided at the location of the monitoring device 20 , the communication module 60 may also be configured to use a communication connection based on mobile network technologies such as GSM, LTE and / or 5G.

[0077] Each of the monitoring devices 20 also includes an internal energy storage device 62 that provides the power required to operate the components of the respective monitoring device 20 .

[0078] The cathodic protection system 10 further includes two gateway devices 64 and a central processing device 66 .

[0079] The gateway devices 64 each include a gateway communication module 68 that is configured to establish a bidirectional communication link with the monitoring device 20 and the central processing device 66, such as Figure 1Therefore, the gateway device 64 serves as a relay station for communication between the monitoring device 20 and the central processing device 66.

[0080] More precisely, the gateway communication module 68 is configured to act both as a LoRa communication module for bidirectional communication with the monitoring devices 20 and as a mobile network module for bidirectional communication with the central processing device 66. In this way, only the gateway device 64 must be located at a location where a stable mobile connection is available, while the monitoring device 20 can be placed arbitrarily near the metal structure 12 as long as it is possible to establish a stable connection with at least one of the gateway devices 64 via LoRaWAN.

[0081] The gateway device 64 also includes an internal gateway energy storage device 69 for powering the gateway device 64, a gateway control module 70 for operating the components of the gateway device 64, and an optional gateway memory unit 72. If the communication between the corresponding gateway device 64 and the central processing device 66 is temporarily interrupted, the signal obtained from the monitoring device 20 can be temporarily stored in the gateway memory unit 72.

[0082] exist Figure 1 In the embodiment shown in FIG. 1 , two gateway devices 64 are used. However, a single gateway device 64 or more than two gateway devices 64 may also be used in the cathodic protection system 10 .

[0083] Each of the monitoring devices 20 is directly connected to one or more of the gateway devices 64. That is, there are no communication links between any of the monitoring devices 20, so that a star-to-star network architecture is implemented, with the gateway devices 64 acting as nodes of the star.

[0084] Preferably, the gateway device 64 acts only as a relay station between the monitoring device 20 and the central processing device 66, so as to keep the design of the gateway device 64 as simple as possible and its energy consumption as low as possible.

[0085] The central processing device 66 includes a server unit 74 and a user interface 76 .

[0086] The server unit 74 includes a server memory unit 78 for storing data received from the monitoring devices 20 so that the central processing device 66 can be used to build a historical data set that can be analyzed to obtain information about the cathodic protection system and / or the metal structure 12 .

[0087] Additionally, the server unit 74 is configured to function as an NTP server to provide NTP information to the monitoring device 20 .

[0088] The user can interact with the server unit 74 via the user interface 76 , for example for adjusting the predetermined time after which the monitoring device 20 should take measurements and for evaluating the data stored in the server memory unit 78 .

[0089] The mode of operation of the cathodic protection system 10 is described in more detail below.

[0090] First, the cathodic protection system 10 is set up by providing the cathode rectifier 14 and the monitoring device 20 and electrically connecting them to the metal structure 12 .

[0091] Then, the cathode rectifier starts to apply the cathode protection potential V to the metal structure 12. 保护 .

[0092] Furthermore, a gateway device 64 is provided so that each of the monitoring devices 20 can be directly coupled to at least one of the gateway devices 64 that construct a star-to-star network architecture LoRaWAN.

[0093] The gateway device 64 in turn connects to the central processing device 66 based on the mobile network connection, thereby establishing a link between the monitoring device 20 and the central processing device 66 .

[0094] The user selects a predetermined time interval, such as 24 hours, via the user interface 76 of the central processing device 66 and it is forwarded from the central processing device 66 to the monitoring device 20 through the gateway device 64 .

[0095] The predetermined time is used by the control module 56 of each of the monitoring devices 20 to determine a wake-up time at which the corresponding monitoring device 20 should obtain electrical signals indicative of the DC signal and the AC signal of the cathodic protection system 10 .

[0096] Then, the control module 56 switches the corresponding monitoring device 20 to a sleep mode in which only the control module 56 is powered by the internal energy storage device 62 to minimize the energy consumption of the monitoring device 20. Therefore, even the communication module 60 is not powered and cannot contact the monitoring device 20.

[0097] When the wake-up time is reached, the control module 56 switches the monitoring device 20 back to the active mode, in which the sensor module 22 obtains the electrical signal and processes the signal as described above. That is, a first filter, i.e., a hardware-based filter, is applied to the electrical signal to obtain at least one filtered electrical signal, which is converted into at least one digital signal by the analog-to-digital converter 54 and transmitted to the control module 56. The control module 56 applies a second filter, i.e., a software-based filter, to the at least one digital signal to obtain at least one filtered digital signal. The at least one filtered digital signal is then forwarded to the central processing device 66 via the gateway device 64 connected to the corresponding monitoring device, where the obtained data is stored in the server memory unit 78.

[0098] In addition to the at least one digital filtered signal, the monitoring devices 20 may also forward additional information to the central processing device 66, such as an identifier of the respective monitoring device 20, status information, a signal strength indicator, a battery health indicator, and / or a ping counter.

[0099] Moreover, the gateway device 64 may add additional information to the data forwarded to the central processing device 66 , such as a gateway identifier, gateway status information, hardware information, software information, a gateway signal strength indicator, and the number of monitoring devices 20 connected to the gateway device 64 .

[0100] After forwarding the at least one filtered digital signal to the central processing device 66, the monitoring device 20 remains in the active mode for a predetermined waiting period. The waiting period preferably has a duration of 5 minutes or less.

[0101] During the waiting period, the monitoring device 20 may receive further instructions and / or information from the central processing device 66, in particular an updated scheduled time based on the NTP server functionality of the central processing device 66. Thus, it may be ensured that the monitoring device 20 remains time coordinated, since the same next wake-up time may be calculated based on the updated scheduled time, or, if the central processing device 66 does not send an updated scheduled time, then the next wake-up time may be calculated based on a scheduled time already available to the control module 56.

[0102] The control module 56 then switches the monitoring unit back into sleep mode, where again only the control module 56 is powered by the internal energy storage device.

[0103] When the next wake-up time arrives, the next measurement and data transfer cycle begins.

[0104] Thus, the monitoring device 20 of the cathodic protection system 10 can be operated with minimal energy consumption while regularly providing information about the status of the cathodic protection system 10 and / or the monitored metal structure 12. Thus, the corrosion process of the metal structure 12 and the atmospheric changes in and around the metal structure 12 can be estimated over an extended period of time without the need for personnel to manually check the status of the cathodic protection system 10, in particular the status of the monitoring device 20 and the gateway device 64.

[0105] Thus, it may be reliably assessed whether the cathodic protection system 10 is operating as intended and whether the metal structure 12 is not experiencing fatal corrosion effects, such that downtime and maintenance windows may be minimized and potential failure of the metal structure 12 may be predicted and thereby avoided.

Claims

1. A monitoring device (20) for a cathodic protection system (10) for a metal structure (12), comprising: a sensor module (22) connectable to the metal structure (12) and configured to measure electrical signals indicative of a DC signal and an AC signal of the cathodic protection system (10), a control module (56) operably coupled to the sensor module (22), the control module (56) being configured to process signals obtained from the sensor module (22) and to switch the monitoring device (20) between a sleep mode and an active mode, and a communication module (60) operatively coupled to the control module (56) for forwarding signals received from the control module (56) to a central processing device (66) of the cathodic protection system (10), in, The monitoring device (20) is configured to: obtain the electrical signal from the sensor module (22) when in the active mode, - applying a first filter to the electrical signal using a filter circuit (26) of the sensor module (22) to obtain at least one filtered electrical signal, - converting the at least one filtered electrical signal into at least one digital signal by an analog-to-digital converter (54) and transmitting the at least one digital signal to the control module (56), - applying a second filter to said at least one digital signal by applying a filtering function in said control module (56) to obtain at least one filtered digital signal, and - forwarding the at least one filtered digital signal by the communication module (60) to the central processing device (66).

2. The monitoring device (20) according to claim 1, wherein: The filter circuit (26) is configured to separate a DC signal and an AC signal when processing the electrical signal, so that a filtered DC signal and a filtered AC signal are obtained.

3. The monitoring device (20) according to claim 1 or 2, wherein: The filter circuit (26) includes a low-pass filter (28) and a high-pass filter (30).

4. The monitoring device (20) according to any one of the preceding claims, wherein: The communication module (60) is a LoRa communication module.

5. The monitoring device (20) according to any one of the preceding claims, wherein The sensor module (22) includes a first shunt resistor (46) and a second shunt resistor (48), wherein the first shunt resistor (46) has a different maximum operating current than the second shunt resistor (48).

6. The monitoring device (20) according to any one of the preceding claims, wherein: The monitoring device (20) comprises a memory module (58) for storing the at least one filtered digital signal.

7. The monitoring device (20) according to any one of the preceding claims, wherein: In the sleep mode of the monitoring device (20), only the control module (56) is connected to the internal energy storage device (62) of the monitoring device (20).

8. The monitoring device (20) according to any one of the preceding claims, wherein: The control module (56) is configured to switch the monitoring device (20) from the sleep mode to the active mode after a predetermined time interval.

9. A cathodic protection system (10) for protecting a metal structure (12), the cathodic protection system (10) comprising a cathode rectifier (14), electrically connected to the metal structure (12), for applying a cathode protection voltage between the metal structure (12) and a reference electrode (18), a plurality of monitoring devices (20) according to any one of the preceding claims, electrically connected to the metal structure (12), one or more gateway devices (64), wherein each monitoring device (20) of the plurality of monitoring devices (20) is communicatively coupled to at least one of the gateway devices (64), and A central processing device (66) is communicatively coupled to the gateway device (64).

10. The cathodic protection system (10) according to claim 9, wherein: Each of the monitoring devices (20) is directly coupled to the one or more gateway devices (64), in particular via a local network protocol.

11. The cathodic protection system (10) according to claim 9 or 10, wherein: The one or more gateway devices (64) are connected to the central processing device (66) via a mobile communication network.

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