Device, system and method for fault detection

Abstract

The present invention relates to a fault current detection device for overhead power transmission lines. The fault current detection device is configured to apply a fault detection algorithm including a duration test and a return-to-normal test. The fault current detection device reports the fault current to a remote fault monitoring device only if both tests are passed. The fault monitoring device is configured to apply an alert ranking algorithm to determine which of a plurality of fault current detection devices is closest to the fault. The alert ranking algorithm includes locating or verifying an upstream source associated with the fault current detection device and classifying the fault current detection device furthest downstream from the upstream source as closest to the fault. Such a fault current detection method and system are disclosed.

Description

[Technical Field]

[0001] The present invention relates to devices, systems and methods for fault detection, in particular (but not exclusively) for fault current detection in medium-voltage (MV) networks. [Background technology]

[0002] In power distribution, MV networks often extend over hundreds of kilometers. Thus, locating faults in these networks can be a long and difficult process that can leave customers without electricity for hours or even days. This has adverse effects on citizens' daily lives and the functioning of the economy.

[0003] Fault sensing or detection devices, also referred to as fault indicators, can reduce the time it takes for field service staff to locate faults in these networks by ensuring that the field service staff begins the fault discovery process closer to the location of the fault. Various types of fault current indicators exist for use on overhead lines, such as conductor-mounted devices and pole-mounted devices. However, there are a number of drawbacks that the applicant has noticed with current fault current indicators.

[0004] Applicant has found that due to the relatively high cost of existing fault indicators, it is typically not possible to install existing fault indicators at every desired location in a network. Instead, existing fault indicators may typically be installed in strategic locations based on factors such as failure history or geographic topography.

[0005] Fault indicators can also be susceptible to false triggering: for example, a lightning surge or load change can cause such devices to erroneously report a fault current, leading to unnecessary time, effort, and cost in investigating the false alarm.

[0006] Furthermore, if fault indicators are installed throughout a voltage network, a fault current may result in several fault indicators being triggered and reporting or indicating a fault. While this provides a useful starting point for field service staff, locating the fault indicator closest to the fault and identifying the source of the problem can still be difficult and time consuming.

[0007] The present invention aims to address or mitigate, at least to some extent, the problems discussed above, thereby assisting in the efficient diagnosis, location and / or repair of problems on power transmission lines. Summary of the Invention

[0008] According to a first aspect of the present invention, there is provided a fault current detection device, comprising: a housing configured to be mounted to a support structure of an overhead power transmission line; a magnetic field sensor disposed in or on the housing and configured to be positioned near, but not directly contacting, an electrical conductor of an overhead power transmission line, the magnetic field sensor configured to obtain magnetic field measurements; a processing component disposed in or on the housing, the processing component configured to analyze measurements taken by the magnetic field sensor and to apply a fault detection algorithm when it detects a change in the magnetic field value that exceeds a predetermined threshold, the fault detection algorithm including a duration test that is passed if the change occurs for longer than a predetermined period of time and a return-to-normal test that is passed if the magnetic field value substantially returns to a normal or previous level following the change, the processing component configured to classify a change as a fault current only if the change passes both the duration test and the return-to-normal test; a communications module disposed in or on the housing and configured to send a fault alert to a remote fault monitoring device in response to the processing component classifying the change as a fault current; a power supply for powering the magnetic field sensor, the processing component, and the communication module; Equipped with.

[0009] The magnetic field measurement may be a measurement of magnetic flux density or magnetic field strength. Thus, the magnetic field value may be the magnetic flux density or magnetic field strength measured by a magnetic field sensor, and the change may be a predetermined change in the magnetic flux density or magnetic field strength.

[0010] In an embodiment of the present invention, a change is classified as a fault only if it exceeds an initial threshold. The threshold is preferably a user-selectable threshold. In such a case, once the threshold is exceeded, the fault current detection device samples data (measurements) from the magnetic field sensor, which is then subjected to a duration test and a return-to-normal test. The data may be sampled for approximately 100 to 300 milliseconds, for example, approximately 200 milliseconds.

[0011] The housing may include a mounting arrangement that allows the fault current detection device to be mounted to a support structure. The support structure may be a pole, and the fault current detection device may be strapped to the pole so that it is positioned closer than about 5 m to the conductor, preferably about 2.5 m below the conductor when in use. The fault current detection device may be portable.

[0012] The magnetic field sensor may be a magnetometer or a digital compass sensor, and is preferably a three-axis magnetometer.

[0013] The communication module may include a GSM (Global System for Mobile communications) or GPRS (General Packet Radio Service) module or other suitable communication module.

[0014] The fault monitoring device may be a master station connected or connectable to the fault current detection device.

[0015] The processing component may be configured to receive remote configuration instructions from a remote fault monitoring device, e.g., a remote master station. Parameters used by the processing component, such as thresholds, electrical network name, location of operation / device location, device priority number, and frequency at or using which the device must "check in" to the fault monitoring device to maintain its status as active with the fault monitoring device, may be modified based on the configuration instructions.

[0016] The power source may be rechargeable and may be a solar-powered device including a solar panel mounted on the outside of the housing and one or more rechargeable batteries connected to the solar panel to provide power to the magnetic field sensor, processing components, and communications module.

[0017] According to a second aspect of the present invention, there is provided a fault current detection method, the fault current detection method comprising: obtaining magnetic field measurements using a sensor positioned near, but not directly contacting, the electrical conductors of the overhead power transmission line; analyzing, by a processing component, measurements taken by the sensor; applying, using a processing component, upon detecting a change in the magnetic field value that exceeds a predetermined threshold, a fault detection algorithm that includes a duration test that passes if the change occurs for more than a predetermined period of time, and a return-to-normal test that passes if the magnetic field value substantially returns to its normal or previous level following the change; classifying the change as a fault current if the change passes both the duration test and the return to normal test; sending a fault alert to a remote fault monitoring device in response to classifying the change as a fault current; Includes:

[0018] According to a third aspect of the present invention, there is provided a fault detection system, the fault detection system comprising: a plurality of fault current detection devices installed throughout a network of overhead power transmission lines; a fault monitoring device communicatively coupled to the fault current detection device, the fault monitoring device comprising: a receiving module for receiving a fault alert from the fault current detection device indicative of a fault current in the network; a processor configured to apply an alert ranking algorithm to determine which fault current detection device is closest to the fault when the subset of fault current detection devices each send a fault alert to the fault monitoring device, the alert ranking algorithm including identifying or validating a location of each of the subset of fault current detection devices, identifying or validating a location of an upstream source associated with the subset of fault current detection devices, and classifying the fault current detection device in the subset most downstream from the upstream source as closest to the fault; and a transmitting module for transmitting a fault location alert indicating the location of the nearest fault current detection device and / or the location of the fault; a fault monitoring device, Equipped with.

[0019] The fault monitoring device may be a master station connected or connectable to all of the fault current detection devices.

[0020] The network may be a medium voltage (MV) network.

[0021] The processor of the fault monitoring device may be configured to rank the subset of fault current detection devices based on their respective distance from the upstream source, with the fault current detection device having the highest or lowest rank (depending on the implementation of the algorithm) belonging to the fault current detection device closest to the fault.

[0022] Preferably, each of the fault current detection devices is a detection device as defined above (for example as defined with reference to the first and second aspects of the invention).

[0023] The transmission module may be configured to transmit the fault location alert to one or more user devices.

[0024] According to a fourth aspect of the present invention, there is provided a fault detection method, the fault detection method comprising: receiving a fault alert from each of a plurality of fault current detection devices installed throughout a network of overhead power transmission lines; applying, by the processor, an alert ranking algorithm to determine which fault current detection device is closest to the fault, the alert ranking algorithm comprising: Identifying or verifying the location of each of the fault current detection devices; Identifying or verifying the location of an upstream source relative to the fault current detection device; and determining which fault current detection device is closest to the fault, including classifying the fault current detection device most downstream from the upstream source as closest to the fault; sending a fault location alert indicating the location of the nearest fault current detection device and / or the location of the fault; Includes:

[0025] Preferably, each of the fault current detection devices is a detection device as defined above (for example as defined with reference to the first and second aspects of the invention).

[0026] The method may include a step of ranking the fault current detection devices based on their respective distance from the upstream source, with the fault current detection device having the highest or lowest ranking (depending on the implementation of the algorithm) belonging to the fault current detection device closest to the fault.

[0027] The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a schematic diagram of an embodiment of a fault detection system according to the present invention; [Figure 2] 2 is a block diagram showing logical / functional components of an embodiment of a fault current detection device ("detection device") and an embodiment of a fault monitoring device ("master") that form part of the system of FIG. 1; [Figure 3] 1 is a perspective view of an exemplary embodiment of a fault current detection device according to the present invention; [Figure 4] FIG. 4 is another perspective view of the device of FIG. 3. [Figure 5] FIG. 4 is a side view of the device of FIG. 3. [Figure 6] FIG. 4 is an opposite side view of the device of FIG. 3. [Figure 7] 7 shows a three-dimensional view of the fault current detection device of FIGS. 3 to 6 mounted on a transmission line pole. [Figure 8] 7 shows a three-dimensional view of the fault current detection device of FIGS. 3 to 6 mounted on a transmission line pole. [Figure 9] 1 is a graph showing magnetic field changes due to lightning to illustrate the application of the fault detection algorithm; [Figure 10] 10 is a graph showing magnetic field changes due to load changes to further illustrate the application of the fault detection algorithm; [Figure 11] 10 is a graph showing magnetic field changes due to fault current to further illustrate the application of the fault detection algorithm; [Figure 12] 1 is a schematic diagram of a network of fault current detection devices coupled to an upstream source ("Source"). [Figure 13] FIG. 13 is another schematic diagram of the network of FIG. 12 illustrating the application of an alert ranking algorithm. [Figure 14] FIG. 10 is a schematic diagram of another network of fault current detection devices shown with two section breakers. [Figure 15]15 is a table containing test data obtained from the fault current detection device of FIG. 14 and the application of an alert ranking algorithm to the test data. DETAILED DESCRIPTION OF THE INVENTION

[0029] The following description of the present invention is provided as an enabling teaching and is an explanation of the principles of the present invention, not intended to limit the scope of the present invention. It will be understood that changes may be made to the embodiment(s) described and illustrated while still achieving the beneficial results of the present invention. It will further be understood that some advantages of the present invention may be achieved by selecting some of the features of the present invention without utilizing other features. Thus, those skilled in the art will recognize that modifications and adaptations to the present invention are possible and may even be desirable in certain circumstances and are a part of the present invention.

[0030] 1 , fault current detection devices 10 (hereinafter "detection devices 10") are installed at various points throughout a medium voltage (MV) electrical distribution network to detect and report fault currents to a remote fault monitoring device in the form of a main station 50. The main station 50 analyzes fault alerts received by the main station 50 from the detection devices 10 and alerts user devices 80, 82, 84 of the fault location or zone in the network. In this exemplary embodiment, the devices 10, 50, 80, 82, 84 communicate via a suitable cellular network. However, it will be appreciated that the devices 10, 50, 80, 82, 84 may communicate using other networks or protocols, for example, via the Internet.

[0031] The detection device 10 is pole-mounted, i.e., the detection device 10 is mounted on a support structure in the form of a pole 12 of the overhead power transmission line 14. The detection device 10 is preferably positioned approximately 2.5 m below the electrical conductor 16 of the line 14 (see also the examples in Figures 7 and 8).

[0032] The components of the detection device 10 and master station 50 are logically illustrated in Figure 2. The detection device 10 has a housing 18 that houses an 8 cm x 6 cm circuit board that contains the magnetic field sensor 20 and provides the functionality of a processing component 22 and a communications module 24. A rechargeable battery pack 28 is also housed in the housing 18 and coupled to the circuit board. The detection device 10 further includes a solar panel 30 that charges the battery 28 during use.

[0033] In this exemplary embodiment, magnetic field sensor 20 is a Honeywell HMC5883L digital compass sensor, which is a three-axis magnetometer configured to measure both the direction and magnitude of a magnetic field. Thus, in use, magnetic field sensor 20 obtains and reports magnetic field measurements, in this case measurements of magnetic flux density (measured in Gauss / Tesla).

[0034] The processing component 22 is configured to analyze the measurements taken by the magnetic field sensor 20 and to apply fault detection algorithms to the measurements, which are described in more detail below with reference to Figures 9 to 11.

[0035] In this embodiment, the communication module 24 is a GSM module configured to send data to and receive data from the master station 50. In particular, the communication module 24 sends a fault alert to the master station 50 when a fault current is detected and classified as a fault by the detection device 10. The communication module 24 may also be configured to receive instructions from the master station 50, such as configuration instructions to change a fault threshold of the device 10 or instructions regarding parameters to apply to a fault detection algorithm used by the device 10.

[0036] The device 10 is also configured to implement battery and sensor alarms and includes a self-resetting watchdog timer (see number 26 in FIG. 2).

[0037] As mentioned above, in this exemplary embodiment, the power source is in the form of a solar power generator. Solar panel 30 is mounted on the outside of housing 18 and is used to charge battery pack 28, ensuring that the above-mentioned components of detection device 10 are powered.

[0038] The housing 18 of an exemplary version of the device 10 is illustrated in Figures 3-6, and includes a mounting arrangement in the form of a bracket 32 ​​that allows the housing 18 to be mounted to a pole. Referring to the example in Figures 7 and 8, the device 10 can be mounted to poles 34, 36 using a strap / band 38 that is threaded through the bracket 32 ​​and secured to the poles 34, 36. For example, a BAND-IT™ stainless steel band or similar strap / band may be used for this purpose.

[0039] 5 and 6, in addition to the panel 30, the exterior of the detection device 10 may include an off / on switch 40 and a light 42 that can be used to indicate whether the detection device 10 is activated and / or to indicate that a fault has been detected. The device 10 also includes a push button 44. The button 44 can be used to force the device 10 into a configuration mode in which the device 10 receives new settings. The button 44 is pressed while the device 10 is switched on to force the device 10 into configuration mode. Once settings are received from the master station 50, the device 10 automatically reboots and "checks in" with the master station 50 with the newly received settings. The settings may include, but are not limited to, the electrical network name, operating location (where the device 10 is installed), alarm thresholds, device priority number, and "check-in" frequency.

[0040] As mentioned above, the master station 50 may communicate with any number of sensing devices 10 across the network. Typically, the master station 50, in use, may communicate with hundreds or thousands of these sensing devices 10 (sometimes across different / heterogeneous power distribution networks).

[0041] As shown in Figure 2, the main station 50 includes a receiving module 52 for receiving fault alerts from the detection devices 10 indicative of fault currents detected on the overhead lines. The main station 50 also includes a processor 54 configured to apply an alert ranking algorithm, which is described in more detail below with reference to Figures 12-15. The main station 50 also includes a transmitting module 56 for sending fault location alerts to user devices 80, 82, 84. The user devices 80, 82, 84 may be devices of field staff, supervisors, managers, etc., for notifying these people of the fault.

[0042] The fault location alert may indicate the location of the fault or the location of the detection device 10 closest to the fault, as confirmed by the master station 50 using an alert ranking algorithm. In some cases, the fault location alert may simply include the name or another identifier of the device 10 or other network component closest to the fault. The master station may also include an appropriate alarm 58, for example, a conventional battery alarm and / or an error alarm, and an appropriate power source 60, such as a rechargeable battery or a mains power connection.

[0043] In use, fault currents can produce large changes in the magnetic field that can be detected by the sensor 20 of the detection device 10. Hence, the presence or passage of a fault current in an MV network is detected by placing the sensor 20 in the vicinity of the relevant line(s). However, magnetometers also react to surges (e.g., those resulting from lightning) and load shifts (e.g., those occurring at the beginning and end of peak electricity usage periods). Hence, the detection device 10 is specifically configured to detect and filter out surges and shifts that are not caused by faults, ensuring that faults are not falsely / unnecessarily reported.

[0044] To detect and filter out these "false positives," device 10 employs a fault detection algorithm. When sensor 20 detects a change in the magnetic field value it measures, a duration test and a return-to-normal test are applied to the measured sensor data. The change must exceed a predetermined threshold, which may be user-selectable, to filter out changes that are too small / insignificant. The duration test is passed if the change occurs for longer than a predetermined period, and the return-to-normal test is passed if the value substantially returns to its normal or previous level following the change. In this exemplary embodiment, the return-to-normal test works as follows: the magnetic field must return to normal after 100 ms but not within 200 ms of the sample period following crossing the user-selectable alarm threshold.

[0045] The detection device 10 is configured and programmed so that both the duration test and the return to normal test must be passed before the change is classified as a fault and reported to the master station 50 .

[0046] As a first example, Figure 9 shows how a duration test can prevent a lightning surge from being reported to the main station 50. As illustrated in Figure 9, as a result of lightning, there may be a very short spike in magnetic flux density, for example, from about 1 Gauss (0.0001 Tesla) to between 7-8 Gauss (0.0007-0.0008 Tesla). However, because this change occurred only for a short period of time, it would not pass the duration test and would not be classified as a fault current (even though it would pass the return-to-normal test).

[0047] As a second example, FIG. 10 illustrates how a return-to-normal test prevents a load increase / decrease from being reported to the master station 50. As illustrated in FIG. 10, as a result of an increase in load due to the onset of a peak usage period, there may be an increase in magnetic flux density, for example, from about 1 Gauss (0.0001 Tesla) to about 2 Gauss (0.0007-0.0008 Tesla). However, because the value did not return to normal after the change (it remains high for the duration of the peak period), the change does not pass the return-to-normal test and is not classified as a fault current (even though it passes the duration test). In this exemplary embodiment, the magnetic field must return to normal after the midpoint (100 ms) of the 200 ms period during which the device 10 collects / samples additional data used to determine the validity of the fault.

[0048] As a third example, Figure 11 illustrates a fault profile that leads to a fault that is actually reported to the master station 50. In the case of Figure 11, as a result of the presence / passage of a fault current, the magnetic field measurements by the sensor 20 change for longer than a predetermined period (thus passing the duration test) and then return to normal (thus passing the return to normal test). Thus, in response to detecting the profile illustrated in Figure 11, the detection device 10 classifies the change as a fault current and sends a fault alert to the master station 50.

[0049] It will be appreciated that when detection devices 10 are installed throughout a network, a fault current may result in several devices 10 being triggered to report or signal the fault to the master station 50, essentially defining a "fault current path." The master station 50 is specifically configured to use the detection devices as "fault path indicators" (hence abbreviated as "FPI" in Figures 12-14) to identify the detection device closest to the fault.

[0050] The master station 50 in this exemplary embodiment is configured to automate this process through an alert ranking algorithm that ranks the detecting devices 10 based on their location on the network. In this embodiment, the master station 50 identifies the highest ranked detecting device as belonging to the detecting device closest to the failure.

[0051] When several detection devices each send a fault alert to the master station 50, an alert ranking algorithm is initiated, which includes the following steps: - determining the location of each of the detection devices that reported a fault; Identifying the location of upstream sources (typically the nearest upstream power plant or sub-power plant) associated with these detection devices; classifying the detection device most downstream from the upstream source as closest to the failure; Includes:

[0052] 12 and 13, the processor 54 ranks the detection devices (FPIs) according to their distance from the upstream source. For example, as illustrated in Figures 12 and 13, the closest detection device may be given a priority number "n," which may be incremented by 1 as the processor 54 proceeds downstream, so that the farthest detection device(s) have the highest priority / ranking.

[0053] Referring to the example of FIG. 14, the following detection devices (FPIs) at the following locations have reported fault alerts to the master station 50: T779L1 T833L1 ·S3309 S2500

[0054] The main station 50 then needs to determine which detection device is closest to the fault, i.e., which alarm message corresponds to the most “reasonable” device, to help the technician / staff locate the fault or locate the fault more quickly / efficiently. To do this, the main station 50 implements a ranking algorithm. Thus, the FPI at location T779L1 is ranked “1” because it is closest to the upstream source, and as the algorithm progresses downstream, the FPIs at T833L1, S3309, and S2500 are ranked “2,” “3,” and “4,” respectively. Thus, the FPI at location S2500 is classified as closest to the fault (since it has the highest ranking / priority), and the fault current path becomes as shown in FIG. 14 . For example, the fault might be a faulty transformer downstream / beyond S2500. A fault location alert can then be sent to the user devices 80, 82, 84 indicating this location or some other identifier useful for locating the fault.

[0055] Figure 15 illustrates an exemplary data set that may be analyzed by the master station 50. In the example of Figure 15, five sets of faults were detected by the four detection devices (FPIs) in question, and the detection devices 10 in question sent fault alerts (containing some of the data shown in Figure 15) to the master station 50. The ranking of the devices is shown in the "Priority" column in Figure 15.

[0056] Applicant believes that embodiments of the present invention may provide many technical advantages: The detection devices described herein are relatively low-cost devices, allowing these devices to be installed more widely throughout a network, even in areas where only "2G" cellular coverage is available.

[0057] Additionally, fault detection algorithms may prevent or reduce false triggers, while alert prioritization algorithms may assist staff / technicians in quickly locating and attending to faults. It has been found that these fault location alerts can be sent to relevant user devices in less than two minutes of the occurrence of a fault.

[0058] The duration test and return-to-normal test are preferably performed on the detection device 10 before an alert is issued, and the use of a three-axis magnetometer may allow the detection device 10 to ignore triggers that do not come from overhead lines. Additionally, the use of a three-axis magnetometer may allow solar panels to be used with the detection device 10 without degrading the device's 10 ability to sense fault currents and allow for flexible orientation of the device 10. The use of solar panels can be beneficial to reduce the running costs of devices of this nature. Long-life batteries are typically expensive and only last 18 months, but rechargeable batteries are cheaper and can last for several years. Because the detection device 10 is configured to be installed 2.5 m below the conductor and fixed to a very high pole above ground level, the risk of theft is very low.

Claims

1. a housing configured to be mounted to a support structure of an overhead power transmission line; a magnetic field sensor disposed within or on the housing, the magnetic field sensor configured to be positioned proximate to but not in direct contact with an electrical conductor of the overhead power transmission line, the magnetic field sensor configured to obtain magnetic field measurements; and a processing component disposed in or on the housing, the processing component configured to analyze the magnetic field measurements taken by the magnetic field sensor and to apply a fault detection algorithm when a change exceeding a predetermined threshold is detected in the magnetic field measurements, the fault detection algorithm including a duration test that is passed if the change occurs for longer than a predetermined period of time, and a return-to-normal test that is passed if the magnetic field measurement substantially returns to a normal or previous level following the change, the processing component configured to classify the change as a fault current only if the change passes both the duration test and the return-to-normal test; a communication module disposed in or on the housing and configured to send a fault alert to a remote master station if the processing component classifies the change as a fault current, the master station configured to communicate with a plurality of fault current detection devices and comprising a processor, the processor configured to, when a subset of the fault current detection devices each send a fault alert to the master station, apply an alert ranking algorithm to determine which fault current detection device is closest to a fault, the alert ranking algorithm comprising: identifying or verifying the location of each of the subset of fault current detection devices that define a fault current path; identifying or verifying a location of an upstream source associated with the subset of fault current detection devices, the upstream source being a nearest upstream generating station or substation associated with the subset of fault current detection devices; ranking the subset of fault current detection devices according to their respective distances from the upstream source along the fault current path; classifying the fault current detection devices in the subset furthest downstream from the upstream source along the fault current path as being closest to the fault, either highest or lowest ranking; the communication module, a power supply for powering the magnetic field sensor, the processing component, and the communication module; A fault current detection device comprising:

2. 2. The fault current detection device of claim 1, wherein the magnetic field measurements are measurements of magnetic flux density or measurements of magnetic field strength.

3. The fault current detection device according to claim 1 or 2, wherein the magnetic field sensor is a magnetometer or a digital compass sensor.

4. The fault current detection device of claim 3 , wherein the magnetic field sensor is a three-axis magnetometer.

5. A fault current detection device according to any one of claims 1 to 4, wherein the housing includes a mounting arrangement that enables the fault current detection device to be mounted to the support structure.

6. 6. The fault current detection device of claim 5, wherein the support structure is a pillar, and the fault current detection device is configured to be mounted on the pillar so as to be positioned within about 5 m of the electrical conductor.

7. 7. The fault current detection device of claim 6, wherein the fault current detection device is configured to be mounted approximately 2.5 m below the electrical conductor.

8. The fault current detection device according to any one of claims 1 to 7, wherein the communication module is a GSM (Global System for Mobile communications) module.

9. The fault current detection device according to any one of claims 1 to 8, wherein the communication module is configured to receive remote setting instructions from the master station.

10. A fault current detection device according to any one of claims 1 to 9, wherein the power source is rechargeable.

11. The power source a solar panel attached to the outside of the housing; one or more rechargeable batteries connected to the solar panel for providing power to the magnetic field sensor, the processing component, and the communication module; 11. The fault current detection device of claim 10, which is a photovoltaic power generation device comprising:

12. the change is classified as a fault only if the change exceeds an initial threshold; A fault current detection device according to any preceding claim, wherein the initial threshold value is a user selectable threshold value.

13. The fault current detection device comprises: The fault current detection device of claim 12 configured to sample data from the magnetic field sensor when the change exceeds the initial threshold, and the data is subjected to the duration test and the return to normal test.

14. obtaining magnetic field measurements using a magnetic field sensor positioned near an electrical conductor of an overhead power transmission line but not in direct contact with said electrical conductor; analyzing, by a processing component, the magnetic field measurements obtained by the magnetic field sensors; if a change in magnetic field value exceeding a predetermined threshold is detected, applying, using said processing component, a fault detection algorithm including a duration test which is passed if said change occurs for longer than a predetermined period of time, and a return-to-normal test which is passed if said magnetic field measurement substantially returns to normal or a previous level following said change; classifying the change as a fault current if the change passes both the duration test and the return to normal test; sending a fault alert to a master station if the change is classified as a fault current, the master station configured to be in communication with a plurality of fault current detection devices, the master station comprising a processor, the processor configured to, when a subset of the fault current detection devices each send a fault alert to the master station, apply an alert ranking algorithm to determine which fault current detection device is closest to the fault, the alert ranking algorithm comprising: identifying or verifying the location of each of the subset of fault current detection devices that define a fault current path; identifying or verifying a location of an upstream source associated with the subset of fault current detection devices, the upstream source being a nearest upstream generating station or substation associated with the subset of fault current detection devices; ranking the subset of fault current detection devices according to their respective distances from the upstream source along the fault current path; classifying the fault current detection devices in the subset furthest downstream from the upstream source along the fault current path as being closest to the fault, either highest or lowest ranking; sending said fault alert, A fault current detection method comprising:

15. the magnetic field sensor and the processing component A magnetic field sensor and processing components provided in a fault current detection device according to any one of claims 1 to 13.

15. The fault current detection method of claim 14.

16. a plurality of fault current detection devices installed throughout a network of overhead power transmission lines, each fault current detection device being a fault current detection device according to any one of claims 1 to 13; a master station capable of communicating with the fault current detection device, a receiving module for receiving a fault alert from the fault current detection device indicative of a fault current in the network; a processor configured to, when the subset of fault current detection devices each transmit a fault alert to the main station, apply an alert ranking algorithm to determine which fault current detection device is closest to the fault, the alert ranking algorithm comprising: identifying or verifying the location of each of the subset of fault current detection devices that define a fault current path; identifying or verifying a location of an upstream source associated with the subset of fault current detection devices, the upstream source being a nearest upstream generating station or substation associated with the subset of fault current detection devices; ranking the subset of fault current detection devices according to their respective distances from the upstream source along the fault current path; classifying the fault current detection devices in the subset furthest downstream from the upstream source along the fault current path as being closest to the fault, either highest or lowest ranking; the processor, a transmitting module for transmitting a fault location alert indicating the location of the nearest fault current detection device and / or the location of the fault; the master station, A fault detection system comprising:

17. The fault detection system of claim 16 , wherein the network is a medium voltage (MV) network.

18. 18. The fault detection system of claim 16 or 17, wherein the transmission module is configured to transmit the fault location alert to one or more user devices.

19. receiving a fault alert from each of a plurality of fault current detection devices installed throughout a network of overhead power transmission lines, each fault current detection device being a fault current detection device according to any one of claims 1 to 13; applying, by a processor, an alert ranking algorithm to determine which fault current detection device is closest to the fault, said alert ranking algorithm comprising: identifying or verifying the location of each of the subset of fault current detection devices that define a fault current path; identifying or verifying a location of an upstream source associated with the subset of fault current detection devices, the upstream source being a nearest upstream generating station or substation associated with the subset of fault current detection devices; ranking the subset of fault current detection devices according to their respective distances from the upstream source along the fault current path; classifying the fault current detection devices in the subset furthest downstream from the upstream source along the fault current path as being closest to the fault, either highest or lowest ranking; the determining step including: sending a fault location alert indicating the location of the nearest fault current detection device and / or the location of the fault; A fault detection method comprising:

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