A ground fault detection system and method

Abstract

The present invention relates to a ground fault detection system and method, belonging to the technical field of electrical engineering fault detection, comprising a data centralized processing module, a first distributed acquisition module and a second distributed acquisition module; the first distributed acquisition module acquires the first waveform data of the upstream monitoring point of the cable to be detected, and sends it to the data centralized processing module; the second distributed acquisition module acquires the second wave recording data of the downstream monitoring point of the cable to be detected, and sends it to the data centralized processing module; the data centralized processing module is used to send a wave recording command to the first distributed acquisition module and the second distributed acquisition module, and receive the first wave recording data and the second wave recording data, and judge whether a ground fault exists based on the received first wave recording data and the second wave recording data. The waveform characteristics of the upstream and downstream monitoring points are used to achieve simultaneous waveform matching in the wave recording waveform, and the data at the same moment is used for differential detection, thereby ensuring the accuracy and sensitivity of fault detection.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical engineering fault detection, and in particular to a ground fault detection system and method. Background Art

[0002] Ground fault is a common fault in low-voltage power distribution system, including two scenarios: phase line connected to the earth and phase line connected to the ground. The protection of ground fault is directly related to the wiring method of low-voltage power distribution system. According to different wiring methods, my country's civil low-voltage power distribution system mainly includes TT, TN-C, TN-CS, and TN-S.

[0003] At present, the TN-CS system is the main wiring method in my country's urban system. The TN-C lines of the TN-CS system are mostly underground cables. In practice, insulation aging and construction damage that lead to cable insulation damage are relatively common. Therefore, the phenomenon of cable grounding leakage is common. Cable leakage will not only cause an abnormal increase in low-voltage line loss in the substation, but also easily cause indirect contact electric shock. For example, once water accumulates on urban public roads during the rainy season and flood season, pedestrians will wade through water or touch public facilities (street lights, bus stops, etc.), which is prone to indirect contact electric shock. Therefore, cable fault detection is particularly important.

[0004] At present, the traditional cable fault detection method uses GPS (or Beidou) satellite synchronization or PMU synchronization to collect data from monitoring points, which is costly and has a prominent problem of poor applicability caused by the obstruction of GPS (or Beidou) satellite signals.

[0005] To this end, the present application provides a ground fault detection system and method. Summary of the invention

[0006] The object of the present invention is to provide a ground fault detection system and method for solving the above technical problems.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] In a first aspect, a ground fault detection system includes a data centralized processing module, a first distributed acquisition module installed at an upstream monitoring point of a cable to be detected, and a second distributed acquisition module installed at a downstream monitoring point of the cable to be detected;

[0009] The data centralized processing module is used to send a wave recording command to the first distributed acquisition module and the second distributed acquisition module;

[0010] The first distributed acquisition module is used to collect the first waveform data of the upstream monitoring point of the cable to be detected, and receive the recording command sent by the data collection processing module, and after receiving the recording command, record the waveform data of the preset time length in the collected first waveform data, obtain the first recorded data, and send the obtained first recorded data to the data collection processing module;

[0011] The second distributed acquisition module is used to collect the second waveform data of the downstream monitoring point of the cable to be detected, and receive the recording command sent by the data collection processing module, and after receiving the recording command, record the waveform data of the preset time length in the collected second waveform data, obtain the second recorded data, and send the obtained second recorded data to the data collection processing module;

[0012] The data concentration processing module is also used to receive the first recording data sent by the first distributed acquisition module and the second recording data sent by the second distributed acquisition module, and determine whether a ground fault exists based on the received first recording data and second recording data.

[0013] Further, the first wave recording data includes the first Phase current waveform data, first Phase current waveform data, first phase current waveform data, first residual current waveform data and first phase voltage waveform data;

[0014] The second recording data includes the second Phase current waveform data, second Phase current waveform data, second phase current waveform data, second residual current waveform data and second phase voltage waveform data.

[0015] Furthermore, the first distributed acquisition module includes:

[0016] First Phase current waveform data acquisition unit, used to collect the first phase current waveform of the upstream monitoring point of the cable to be tested. Phase current waveform data;

[0017] First Phase current waveform data acquisition unit, used to collect the first phase current waveform of the upstream monitoring point of the cable to be tested. Phase current waveform data;

[0018] First Phase current waveform data acquisition unit, used to collect the first phase current waveform of the upstream monitoring point of the cable to be tested. Phase current waveform data;

[0019] A first residual current waveform data acquisition unit, used for acquiring first residual current waveform data of an upstream monitoring point of the cable to be detected;

[0020] A first phase voltage waveform data acquisition unit, used to acquire first phase voltage waveform data of an upstream monitoring point of the cable to be detected;

[0021] A first communication module, used for sending the collected first wave recording data to the data collection processing module, and for receiving the wave recording command sent by the data collection processing module;

[0022] The second distributed acquisition module includes:

[0023] second Phase current waveform data acquisition unit, used to collect the second phase current waveform data of the downstream monitoring point of the cable to be tested. Phase current waveform data;

[0024] second Phase current waveform data acquisition unit, used to collect the second phase current waveform data of the downstream monitoring point of the cable to be tested. Phase current waveform data;

[0025] second Phase current waveform data acquisition unit, used to collect the second phase current waveform data of the downstream monitoring point of the cable to be tested. Phase current waveform data;

[0026] A second residual current waveform data acquisition unit, used for acquiring second residual current waveform data of a downstream monitoring point of the cable to be detected;

[0027] A second phase voltage waveform data acquisition unit, used to acquire second phase voltage waveform data of a downstream monitoring point of the cable to be detected;

[0028] The second communication module is used to send the collected second wave recording data to the data collection processing module, and to receive the wave recording command sent by the data collection processing module.

[0029] Furthermore, the data collection processing module includes:

[0030] A third communication module is used to send a wave recording command to the first distributed acquisition module and the second distributed acquisition module;

[0031] A data receiving module, used for receiving first wave recording data sent by the first distributed acquisition module and second wave recording data sent by the second distributed acquisition module;

[0032] A waveform matching synchronization algorithm unit, used for performing waveform matching on the first recorded waveform data and the second recorded waveform data;

[0033] A differential operation unit, used for performing a differential operation on the first residual current data in the first waveform recording data after waveform matching and the second residual current data in the second waveform recording data after waveform matching;

[0034] A fault criterion building unit, used for building a fault criterion according to the result of the differential operation;

[0035] The fault determination unit is used to determine whether a ground fault occurs according to the constructed fault determination criteria.

[0036] In a second aspect, a ground fault detection method applied to the ground fault detection system according to the above aspects is provided, the method comprising the following specific steps:

[0037] Step S1: Select a cable to be detected, install a first distributed acquisition module at an upstream monitoring point of the cable to be detected, the first distributed acquisition module is used to collect first waveform data of the upstream monitoring point of the cable to be detected, and install a second distributed acquisition module at a downstream monitoring point of the cable to be detected, the second distributed acquisition module is used to collect second waveform data of the downstream monitoring point of the cable to be detected;

[0038] Step S2: The data centralized processing module sends a recording command to the first distributed acquisition module and the second distributed acquisition module respectively;

[0039] Step S3: after receiving the recording command sent by the data collection processing module, the first distributed acquisition module records the waveform data of the preset time length in the collected first waveform data, and after receiving the recording command sent by the data collection processing module, the second distributed acquisition module records the waveform data of the preset time length in the collected second waveform data;

[0040] Step S4: the first distributed acquisition module sends the collected first wave recording data to the data centralized processing module, and the second distributed acquisition module sends the collected second wave recording data to the data centralized processing module;

[0041] Step S5: After receiving the first wave recording data and the second wave recording data, the data concentration processing module uses a waveform matching synchronization algorithm to perform waveform matching on the first wave recording data and the second wave recording data;

[0042] Step S6: After the data concentration processing module completes the waveform matching, a differential operation is performed on the first residual current data in the first waveform recording data after the waveform matching and the second residual current data in the second waveform recording data after the waveform matching, and a fault judgment criterion is constructed according to the differential operation result;

[0043] Step S7: Determine whether a ground fault occurs according to a fault criterion.

[0044] Further, the first wave recording data includes the first Phase current waveform data, first Phase current waveform data, first phase current waveform data, first residual current waveform data and first phase voltage waveform data;

[0045] The second recording data includes the second Phase current waveform data, second Phase current waveform data, second phase current waveform data, second residual current waveform data and second phase voltage waveform data.

[0046] Further, in step S5, waveform matching is performed on the first recorded wave data and the second recorded wave data, including:

[0047] Step S51: For the first Phase current waveform data, first Phase current waveform data and the first The phase current waveform data is low-pass filtered to obtain first low-pass filtered waveform data, the first low-pass filtered waveform data includes first Phase current low-pass filter waveform data, first Phase current low-pass filtered waveform data and the first Phase current low-pass filtered waveform data;

[0048] Step S52: For the second Phase current waveform data, second Phase current waveform data and second The phase current waveform data is low-pass filtered to obtain second low-pass filtered waveform data, the second low-pass filtered waveform data includes a second Phase current low-pass filter waveform data, second Phase current low-pass filtered waveform data and the second Phase current low-pass filtered waveform data;

[0049] Step S53: selecting first waveform data for matching and comparison from the first low-pass filtered waveform data through a first matching window;

[0050] Step S54: selecting second waveform data from the second low-pass filtered waveform data through a second matching window to start waveform matching, wherein the time length of the first matching window is the same as that of the second matching window;

[0051] Step S55: determine whether the first waveform data and the second waveform data meet the waveform matching criterion. If so, execute step S56. If not, determine whether the second waveform data has been traversed. If it is determined that the traversal has been completed, the waveform matching fails and the execution is completed. If it is determined that the traversal has not been completed, move the second matching window, reselect the second waveform data, and continue to return to step S55.

[0052] Step S56: widening the first matching window, widening the second matching window, and performing waveform matching on the first waveform data selected by the widened first matching window and the second waveform data selected by the widened second matching window;

[0053] Step S57: determine whether the first waveform data and the second waveform data meet the waveform matching criterion, if so, the matching is completed, if not, execute step S58;

[0054] Step S58: restore the first matching window and the second matching window to their original sizes, move the second matching window, reselect the second waveform data, and then return to step S55.

[0055] Furthermore, the waveform matching criteria are as follows:

[0056] The match is completed if any of the following criteria is met;

[0057] All three-phase circuits satisfy the waveform matching judgment formula;

[0058] Criterion II:

[0059] In a three-phase circuit, any two-phase circuits satisfy the waveform matching judgment formula, and the other phase circuit satisfies:

[0060]

[0061] In the formula, represents the correlation coefficient of the waveform selected by the first distributed acquisition module and the second distributed acquisition module for identification, represents the second threshold;

[0062] The expression of the waveform matching judgment formula is:

[0063]

[0064] In the formula, Indicates the size of the first matching window, represents the size of the second matching window, Indicates the number of periodic waves in the waveform data, express Phase circuit, , Indicates the first distributed collection module collects Waveform data of phase circuit, Indicates the first Waveform data of phase circuit, Indicates the first threshold.

[0065] Furthermore, the calculation formula for the difference operation is:

[0066]

[0067] In the formula, waveform data representing first residual current data in the first waveform data after waveform matching, waveform data representing second residual current data in the second waveform data after waveform matching, A differential waveform representing the waveform data of the first residual current data after waveform matching and the waveform data of the second residual current data after waveform matching.

[0068] Furthermore, the expression of the fault criterion is:

[0069]

[0070] In the formula, represent The effective value of Indicates the third threshold.

[0071] Beneficial effects of the present invention:

[0072] The first wave recording data and the second wave recording data of the present invention have different recording times. By matching the waveforms of the first wave recording data and the second wave recording data, post-synchronization of the wave recording waveforms is achieved, thereby avoiding the use of a traditional synchronous acquisition method of GPS (or Beidou) satellite synchronization or PMU synchronization, reducing costs, and avoiding the problem of poor applicability of the traditional synchronous acquisition method due to the shielding of GPS (or Beidou) satellite signals.

[0073] The present invention performs waveform matching on the first wave recording data and the second wave recording data at the double detection points, performs differential operation on the first residual current data in the first wave recording data after waveform matching and the second residual current data in the second wave recording data after waveform matching, and performs differential detection on the waveform data matched at the same time, thereby improving the accuracy of fault detection;

[0074] During the waveform matching process, the phase of the collected phase voltage is used as the starting point for selecting the phase current. The electrical parameters such as the phase and frequency of the phase voltage are relatively stable. Therefore, using the phase of the phase voltage as the starting basis for selecting the window data for waveform matching can ensure that the starting phases are the same, and avoid the recognition error caused by the different starting phases of the current waveforms used for waveform matching.

[0075] Two waveform matching criteria, criterion I and criterion II, are set, which fully considers the difference in current waveform amplitude between the upstream monitoring point of the cable to be detected and the downstream monitoring point of the cable to be detected caused by the scenario of large grounding fault current. That is, although the different amplitudes of the upstream monitoring point of the cable to be detected and the downstream monitoring point of the cable to be detected may cause their direct differential waveforms to fail to meet criterion I, their waveform similarity still makes it meet criterion II, making fault detection more reliable and the fault detection sensitivity higher.

[0076] These and other objects, features and advantages of the present invention will be fully reflected in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 The schematic diagram of the detection principle of the ground fault detection system of the present invention is shown.

[0078] Figure 2 A schematic diagram of a waveform matching process of a ground fault detection method of the present invention is shown.

[0079] Figure 3 The first recorded wave data collected by the first distributed collection module of the ground fault detection method of the present invention is shown.

[0080] Figure 4 The second recorded wave data collected by the second distributed collection module of the ground fault detection method of the present invention is shown.

[0081] Figure 5 A schematic diagram showing waveform data comparison between an upstream monitoring point of a cable to be detected and a downstream monitoring point of a cable to be detected in a ground fault detection method of the present invention is shown. DETAILED DESCRIPTION

[0082] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0083] It should be understood by those skilled in the art that, in the disclosure of the specification, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device including a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. Therefore, the above terms should not be understood as limiting the present invention.

[0084] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0085] refer to Figure 1 A ground fault detection system according to a preferred embodiment of the present invention will be described in detail below. The system includes a data centralized processing module, a first distributed acquisition module installed at an upstream monitoring point of the cable to be detected, and a second distributed acquisition module installed at a downstream monitoring point of the cable to be detected.

[0086] The data centralized processing module is used to send a wave recording command to the first distributed acquisition module and the second distributed acquisition module.

[0087] The first distributed acquisition module is used to collect the first waveform data of the upstream monitoring point of the cable to be detected, and receive the recording command sent by the data concentration processing module, and after receiving the recording command, record the waveform data of a preset time length in the collected first waveform data, obtain the first recorded data, and send the obtained first recorded data to the data concentration processing module.

[0088] The second distributed acquisition module is used to collect the second waveform data of the downstream monitoring point of the cable to be detected, and receive the recording command sent by the data concentration processing module, and after receiving the recording command, record the waveform data of a preset time length in the collected second waveform data, obtain the second recorded data, and send the obtained second recorded data to the data concentration processing module.

[0089] The data concentration processing module is also used to receive the first recording data sent by the first distributed acquisition module and the second recording data sent by the second distributed acquisition module, and determine whether a ground fault exists based on the received first recording data and second recording data.

[0090] Waveform matching is performed on the first recorded waveform data and the second recorded waveform data at the double detection points, and a differential operation is performed on the first residual current data in the first recorded waveform data after waveform matching and the second residual current data in the second recorded waveform data after waveform matching. Differential detection is performed on the waveform data matched at the same moment, thereby improving the accuracy of fault detection.

[0091] The waveform characteristics of the upstream and downstream monitoring points are used to achieve simultaneous waveform matching in the recorded waveform, so that differential detection can be performed using the data at the same moment, ensuring the accuracy and sensitivity of fault detection.

[0092] Exemplarily, the first wave recording data includes the first Phase current waveform data, first Phase current waveform data, first phase current waveform data, first residual current waveform data and first phase voltage waveform data;

[0093] The second recording data includes the second Phase current waveform data, second Phase current waveform data, second phase current waveform data, second residual current waveform data and second phase voltage waveform data.

[0094] In this embodiment, the first distributed acquisition module includes:

[0095] First Phase current waveform data acquisition unit, used to collect the first phase current waveform of the upstream monitoring point of the cable to be tested. Phase current waveform data.

[0096] First Phase current waveform data acquisition unit, used to collect the first phase current waveform of the upstream monitoring point of the cable to be tested. Phase current waveform data.

[0097] First Phase current waveform data acquisition unit, used to collect the first phase current waveform of the upstream monitoring point of the cable to be tested. Phase current waveform data.

[0098] The first residual current waveform data acquisition unit is used to acquire the first residual current waveform data of the upstream monitoring point of the cable to be detected.

[0099] The first phase voltage waveform data acquisition unit is used to acquire the first phase voltage waveform data of the upstream monitoring point of the cable to be detected.

[0100] The first communication module is used to send the collected first wave recording data to the data collection processing module, and to receive the wave recording command sent by the data collection processing module.

[0101] The second distributed acquisition module includes:

[0102] second Phase current waveform data acquisition unit, used to collect the second phase current waveform data of the downstream monitoring point of the cable to be tested. Phase current waveform data.

[0103] second Phase current waveform data acquisition unit, used to collect the second phase current waveform data of the downstream monitoring point of the cable to be tested. Phase current waveform data.

[0104] second Phase current waveform data acquisition unit, used to collect the second phase current waveform data of the downstream monitoring point of the cable to be tested. Phase current waveform data.

[0105] The second residual current waveform data acquisition unit is used to acquire the second residual current waveform data of the downstream monitoring point of the cable to be detected.

[0106] The second phase voltage waveform data acquisition unit is used to acquire the second phase voltage waveform data of the downstream monitoring point of the cable to be detected.

[0107] The second communication module is used to send the collected second wave recording data to the data collection processing module, and to receive the wave recording command sent by the data collection processing module.

[0108] In this embodiment, the data collection processing module includes:

[0109] The third communication module is used to send a wave recording command to the first distributed acquisition module and the second distributed acquisition module.

[0110] The data receiving module is used to receive the first recorded wave data sent by the first distributed acquisition module and the second recorded wave data sent by the second distributed acquisition module.

[0111] The waveform matching synchronization algorithm unit is used to perform waveform matching on the first recorded waveform data and the second recorded waveform data.

[0112] The differential operation unit is used to perform differential operation on the first residual current data in the first waveform data after waveform matching and the second residual current data in the second waveform data after waveform matching.

[0113] The fault criterion building unit is used to build a fault criterion according to the result of the differential operation.

[0114] The fault determination unit is used to determine whether a ground fault occurs according to the constructed fault determination criteria.

[0115] refer to Figure 2-Figure 5The present invention further provides a ground fault detection method applied to the ground fault detection system described in the above embodiments, the method comprising steps S1 to S7;

[0116] Step S1: Select a cable to be detected, install a first distributed acquisition module on the upstream monitoring point of the cable to be detected, the first distributed acquisition module is used to collect the first waveform data of the upstream monitoring point of the cable to be detected, and install a second distributed acquisition module on the downstream monitoring point of the cable to be detected, the second distributed acquisition module is used to collect the second waveform data of the downstream monitoring point of the cable to be detected. It can be understood that in a cable line, the starting end or power supply end where the electric energy or signal flows is usually called the upstream of the cable. It is usually a power station, a substation, a distribution board or any other source that provides electric energy or signals.

[0117] Correspondingly, the downstream of the cable refers to the terminal or receiving end to which the electric energy or signal flows. It is usually a load (such as a motor, lighting equipment, communication equipment, etc.), another substation, a distribution point, or any other device that consumes or forwards electric energy or signals. In addition, it can also be understood that in the order from the upstream monitoring point of the cable to be detected to the downstream monitoring point of the cable to be detected, the direction close to the upstream monitoring point of the cable to be detected is called "front", and the direction close to the downstream monitoring point of the cable to be detected is called "back", that is, the second distributed acquisition module is installed before the neutral working grounding point, which means: the second distributed acquisition module is installed between the upstream monitoring point of the cable to be detected and the neutral working grounding point.

[0118] Step S2: The data centralized processing module sends a recording command to the first distributed acquisition module and the second distributed acquisition module respectively. The recording command includes a command to start recording and a recording duration parameter command. The data centralized processing module sends the recording command to the first distributed acquisition module installed at the upstream monitoring point of the cable to be detected and the second distributed acquisition module installed at the downstream monitoring point of the cable to be detected through wireless communication.

[0119] Step S3: After receiving the recording command sent by the data concentration processing module, the first distributed acquisition module records the waveform data of a preset time length in the collected first waveform data, and after receiving the recording command sent by the data concentration processing module, the second distributed acquisition module records the waveform data of a preset time length in the collected second waveform data.

[0120] Step S4: the first distributed acquisition module sends the collected first wave recording data to the data centralized processing module, and the second distributed acquisition module sends the collected second wave recording data to the data centralized processing module.

[0121] Step S5: After receiving the first wave recording data and the second wave recording data, the data concentration processing module uses a waveform matching synchronization algorithm to perform waveform matching on the first wave recording data and the second wave recording data.

[0122] Step S6: After the data concentration processing module completes waveform matching, a differential operation is performed on the first residual current data in the first waveform recording data after waveform matching and the second residual current data in the second waveform recording data after waveform matching, and a fault judgment criterion is constructed according to the differential operation result.

[0123] Step S7: Determine whether a ground fault occurs according to a fault criterion.

[0124] In this embodiment, the invention is described by applying it to a three-phase cable (three phase lines + one neutral line). In practice, the invention is also applicable to a single-phase cable (one phase line + one neutral line, such as a cable for street lamps). The difference is that for a three-phase cable, the waveform matching operation is performed on the currents of the three-phase cables at the same time, while for a single-phase cable, the waveform matching operation is performed only on the current of one-phase cable.

[0125] Waveform matching is performed on the first recorded data and the second recorded data at the double detection points, and a differential operation is performed on the first residual current data in the first recorded data after waveform matching and the second residual current data in the second recorded data after waveform matching, and differential detection is performed on the data at the same time of matching, thereby improving the accuracy of fault detection.

[0126] It can be understood that the first recorded wave data and the second recorded wave data of the present invention have different recording times. By matching the waveforms of the first recorded wave data and the second recorded wave data, post-synchronization of the recorded wave waveforms is achieved, thereby avoiding the use of the traditional GPS (or Beidou) satellite synchronization or PMU synchronization synchronous acquisition method, reducing costs, and avoiding the problem of poor applicability of the traditional synchronous acquisition method due to the shielding of GPS (or Beidou) satellite signals;

[0127] During the waveform matching process, the phase of the collected phase voltage is used as the starting point for selecting the phase current. The electrical parameters such as the phase and frequency of the phase voltage are relatively stable. Therefore, using the phase of the phase voltage as the starting selection basis for the window data for waveform matching can ensure that the starting phases are the same, thereby avoiding recognition errors caused by different starting phases of the current waveforms used for waveform matching.

[0128] During the waveform matching process, starting the matching from the second waveform data of the second matching window can reduce the time of searching for matching data; for the first waveform matching, using a shorter matching window can increase the matching speed; for the second waveform matching, using a longer matching window can ensure the accuracy of the matching. The simultaneous use of two-level waveform matching can ensure the reliability of waveform matching;

[0129] For the waveform matching criteria, setting two waveform matching criteria, Criterion I and Criterion II, fully considers the difference in current waveform amplitude between the upstream monitoring point of the cable to be detected and the downstream monitoring point of the cable to be detected caused by the scenario of large grounding fault current. That is, although the different amplitudes of the upstream monitoring point of the cable to be detected and the downstream monitoring point of the cable to be detected may cause their direct differential waveforms to fail to meet Criterion I, their waveform similarity still makes it meet Criterion II, making fault detection more reliable and the sensitivity of fault detection higher.

[0130] In this embodiment, the first wave recording data includes the first Phase current waveform data, first Phase current waveform data, first phase current waveform data, first residual current waveform data and first phase voltage waveform data;

[0131] The second recording data includes the second Phase current waveform data, second Phase current waveform data, second phase current waveform data, second residual current waveform data and second phase voltage waveform data.

[0132] For example, in combination Figure 2 In step S5, waveform matching is performed on the first wave recording data and the second wave recording data, including:

[0133] Step S51: For the first Phase current waveform data, first Phase current waveform data and the first The phase current waveform data is low-pass filtered to obtain first low-pass filtered waveform data, the first low-pass filtered waveform data includes first Phase current low-pass filter waveform data, first Phase current low-pass filtered waveform data and the first Phase current low-pass filtered waveform data.

[0134] Step S52: For the second Phase current waveform data, second Phase current waveform data and second The phase current waveform data is low-pass filtered to obtain second low-pass filtered waveform data, the second low-pass filtered waveform data includes a second Phase current low-pass filter waveform data, second Phase current low-pass filtered waveform data and the second Phase current low-pass filtered waveform data.

[0135] Step S53: selecting the first waveform data for matching and comparison from the first low-pass filtered waveform data through the first matching window. Figure 3 and Figure 4 The horizontal axis in the coordinate system represents time, Figure 3 represents the first recorded wave data collected by the first distributed collection module, Figure 3 From top to bottom are the first phase voltage waveform data, the first Phase current waveform data, first Phase current waveform data, first Phase current waveform data and first residual current waveform data, the black dotted box represents the waveform data of the first recorded data stored for a preset time length after the first distributed acquisition module receives the recording command.

[0136] Figure 4 represents the second wave recording data collected by the second distributed collection module, Figure 4 From top to bottom are the second phase voltage waveform data, the second Phase current waveform data, second Phase current waveform data, second Phase current waveform data and second residual current waveform data, the black dotted box represents the waveform data of the second recorded data stored for a preset time length after the second distributed acquisition module receives the recording command.

[0137] The data centralized processing module sends recording commands to the first distributed acquisition module and the second distributed acquisition module respectively. There will be a deviation in the time when the first distributed acquisition module and the second distributed acquisition module receive the recording command, that is, it is impossible to ensure that the waveform data is recorded at the same time. Figure 3 and Figure 4 It can be seen that the preset time length is 400ms, the recorded data of the first distributed acquisition module is 100ms-500ms, and the recorded data of the second distributed acquisition module is 300ms-700ms.

[0138] Step S54: Selecting second waveform data from the second low-pass filtered waveform data through a second matching window to start waveform matching, wherein the first matching window and the second matching window have the same time length. Figure 3 The orange dotted box in the figure represents the first matching window. The waveform data selected by the first matching window is the first waveform data. Figure 4 The orange dotted frame in represents the second matching window, and the waveform data selected by the second matching window is the second waveform data.

[0139] Step S55: determine whether the first waveform data and the second waveform data meet the waveform matching criterion. If so, execute step S56. If not, determine whether the second waveform data has been traversed. If it is determined that the traversal has been completed, the waveform matching fails and the execution is completed. If it is determined that the traversal has not been completed, move the second matching window, reselect the second waveform data, and continue to return to step S55.

[0140] Step S56: widen the first matching window, widen the second matching window, and perform waveform matching on the first waveform data selected by the widened first matching window and the second waveform data selected by the widened second matching window. Generally speaking, if only the eyes in the two photos are judged to determine whether they are of the same person, misjudgment may occur, but expanding the judgment area to the entire face greatly improves the accuracy of the judgment.

[0141] Step S57: determine whether the first waveform data and the second waveform data meet the waveform matching criterion, if so, the matching is completed, if not, execute step S58;

[0142] Step S58: restore the first matching window and the second matching window to their original sizes, move the second matching window, reselect the second waveform data, and then return to step S55.

[0143] For the waveform data of the upstream monitoring point and the downstream monitoring point of the cable to be detected, the waveform matching synchronization algorithm can attenuate the high-frequency components in the phase current due to the influence of the line capacitance and inductance parameters (see Figure 3 and Figure 4 ), but the low-frequency waveforms detected by the upstream monitoring point of the cable to be detected and the downstream monitoring point of the cable to be detected are theoretically the same, so the low-frequency waveform can be used to synchronize the monitoring point data.

[0144] Exemplarily, the waveform matching criteria are as follows:

[0145] The match is completed if any of the following criteria is met;

[0146] All three-phase circuits satisfy the waveform matching judgment formula;

[0147] Criterion II:

[0148] In a three-phase circuit, any two-phase circuits satisfy the waveform matching judgment formula, and the other phase circuit satisfies:

[0149]

[0150] In the formula, represents the correlation coefficient of the waveform selected by the first distributed acquisition module and the second distributed acquisition module for identification, represents the second threshold;

[0151] The expression of the waveform matching judgment formula is:

[0152]

[0153] In the formula, Indicates the size of the first matching window, represents the size of the second matching window, Indicates the number of periodic waves in the waveform data, express Phase circuit, , Indicates the first distributed collection module collects Waveform data of phase circuit, Indicates the first Waveform data of phase circuit, Indicates the first threshold.

[0154] Understandably, ,when hour, Indicates the first distributed collection module collects Phase circuit first The waveform data corresponding to the phase current data, namely the first waveform data, Indicates the data collected by the second distributed collection module Phase circuit second Waveform data corresponding to phase current data.

[0155] when hour, Indicates the first distributed collection module collects Phase circuit first The waveform data corresponding to the phase current data, Indicates the data collected by the second distributed collection module Phase circuit second Waveform data corresponding to phase current data.

[0156] when hour, Indicates the first distributed collection module collects Phase circuit first The waveform data corresponding to the phase current data, Indicates the data collected by the second distributed collection module Phase circuit second Waveform data corresponding to phase current data.

[0157] There are two judgment formulas for waveform matching criteria. If any one of the above criteria I and II is met, the matching is completed.

[0158] In this embodiment, the calculation formula for the difference operation is:

[0159]

[0160] In the formula, waveform data representing first residual current data in the first waveform data after waveform matching, waveform data representing second residual current data in the second waveform data after waveform matching, A differential waveform representing the waveform data of the first residual current data after waveform matching and the waveform data of the second residual current data after waveform matching.

[0161] In this embodiment, the expression of the fault criterion is:

[0162]

[0163] In the formula, represent The effective value of Indicates the third threshold.

[0164] Determine whether a ground fault occurs according to the fault criterion. If the above fault criterion is met, When the effective value of is greater than or equal to the third threshold, it is determined that a ground fault occurs. If the above fault criterion is not met, that is, When the effective value of is less than the third threshold, it is determined that no ground fault occurs.

[0165] It should be noted that the terms "first, second" in the present invention are only used for descriptive purposes and do not indicate any order. They cannot be understood as indicating or implying relative importance. These terms can be interpreted as names.

[0166] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The advantages of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

[0167] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The advantages of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

[0168] The algorithm and display provided herein are not inherently related to any particular computer, virtual system or other device. Various general purpose systems can also be used together with the teachings based on this. According to the above description, it is obvious that the structure required for constructing such systems. In addition, the present invention is not directed to any specific programming language either. It should be understood that various programming languages ​​can be utilized to realize the content of the present invention described herein, and the description of the above specific languages ​​is for disclosing the best mode of the present invention.

[0169] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0170] Furthermore, those skilled in the art will appreciate that although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features from different embodiments is meant to be within the scope of the present invention and to form different embodiments.

Claims

1. A ground fault detection method based on a ground fault detection system, characterized in that: The system comprises a data centralized processing module, a first distributed acquisition module installed at an upstream monitoring point of the cable to be detected, and a second distributed acquisition module installed at a downstream monitoring point of the cable to be detected; The data centralized processing module is used to send a wave recording command to the first distributed acquisition module and the second distributed acquisition module; The first distributed acquisition module is used to collect the first waveform data of the upstream monitoring point of the cable to be detected, and receive the recording command sent by the data collection processing module, and after receiving the recording command, record the waveform data of the preset time length in the collected first waveform data, obtain the first recorded data, and send the obtained first recorded data to the data collection processing module; The second distributed acquisition module is used to collect the second waveform data of the downstream monitoring point of the cable to be detected, and receive the recording command sent by the data collection processing module, and after receiving the recording command, record the waveform data of the preset time length in the collected second waveform data, obtain the second recorded data, and send the obtained second recorded data to the data collection processing module; The data centralized processing module is also used to receive the first wave recording data sent by the first distributed acquisition module and the second wave recording data sent by the second distributed acquisition module, and determine whether a ground fault exists based on the received first wave recording data and the second wave recording data; The first distributed acquisition module includes: First Phase current waveform data acquisition unit, used to collect the first phase current waveform of the upstream monitoring point of the cable to be tested. Phase current waveform data; First Phase current waveform data acquisition unit, used to collect the first phase current waveform of the upstream monitoring point of the cable to be tested. Phase current waveform data; First Phase current waveform data acquisition unit, used to collect the first phase current waveform of the upstream monitoring point of the cable to be tested. Phase current waveform data; A first residual current waveform data acquisition unit, used for acquiring first residual current waveform data of an upstream monitoring point of the cable to be detected; A first phase voltage waveform data acquisition unit, used to acquire first phase voltage waveform data of an upstream monitoring point of the cable to be detected; A first communication module, used for sending the collected first wave recording data to the data collection processing module, and for receiving the wave recording command sent by the data collection processing module; The second distributed acquisition module includes: second Phase current waveform data acquisition unit, used to collect the second phase current waveform data of the downstream monitoring point of the cable to be tested. Phase current waveform data; second Phase current waveform data acquisition unit, used to collect the second phase current waveform data of the downstream monitoring point of the cable to be tested. Phase current waveform data; second Phase current waveform data acquisition unit, used to collect the second phase current waveform data of the downstream monitoring point of the cable to be tested. Phase current waveform data; A second residual current waveform data acquisition unit, used for acquiring second residual current waveform data of a downstream monitoring point of the cable to be detected; A second phase voltage waveform data acquisition unit, used to acquire second phase voltage waveform data of a downstream monitoring point of the cable to be detected; A second communication module is used to send the collected second wave recording data to the data collection processing module, and to receive the wave recording command sent by the data collection processing module; The data collection processing modules include: A third communication module is used to send a wave recording command to the first distributed acquisition module and the second distributed acquisition module; A data receiving module, used for receiving first wave recording data sent by the first distributed acquisition module and second wave recording data sent by the second distributed acquisition module; A waveform matching synchronization algorithm unit, used for performing waveform matching on the first recorded waveform data and the second recorded waveform data; A differential operation unit, used for performing a differential operation on the first residual current data in the first waveform recording data after waveform matching and the second residual current data in the second waveform recording data after waveform matching; A fault criterion building unit, used for building a fault criterion according to the result of the differential operation; A fault determination unit, used to determine whether a ground fault occurs according to a constructed fault determination criterion; The method comprises the following specific steps: Step S1: Select a cable to be detected, install a first distributed acquisition module at an upstream monitoring point of the cable to be detected, the first distributed acquisition module is used to collect first waveform data of the upstream monitoring point of the cable to be detected, and install a second distributed acquisition module at a downstream monitoring point of the cable to be detected, the second distributed acquisition module is used to collect second waveform data of the downstream monitoring point of the cable to be detected; Step S2: The data centralized processing module sends a recording command to the first distributed acquisition module and the second distributed acquisition module respectively; Step S3: after receiving the recording command sent by the data collection processing module, the first distributed acquisition module records the waveform data of the preset time length in the collected first waveform data, and after receiving the recording command sent by the data collection processing module, the second distributed acquisition module records the waveform data of the preset time length in the collected second waveform data; Step S4: the first distributed acquisition module sends the collected first wave recording data to the data centralized processing module, and the second distributed acquisition module sends the collected second wave recording data to the data centralized processing module; Step S5: After receiving the first wave recording data and the second wave recording data, the data concentration processing module uses a waveform matching synchronization algorithm to perform waveform matching on the first wave recording data and the second wave recording data; Step S6: After the data concentration processing module completes the waveform matching, a differential operation is performed on the first residual current data in the first waveform recording data after the waveform matching and the second residual current data in the second waveform recording data after the waveform matching, and a fault judgment criterion is constructed according to the differential operation result; Step S7: judging whether a ground fault occurs according to a fault judgment criterion; The first recording data includes the first Phase current waveform data, first Phase current waveform data, first phase current waveform data, first residual current waveform data and first phase voltage waveform data; The second recording data includes the second Phase current waveform data, second Phase current waveform data, second phase current waveform data, second residual current waveform data, and second phase voltage waveform data; In step S5, waveform matching is performed on the first wave recording data and the second wave recording data, including: Step S51: For the first Phase current waveform data, first Phase current waveform data and the first The phase current waveform data is low-pass filtered to obtain first low-pass filtered waveform data, the first low-pass filtered waveform data includes first Phase current low-pass filter waveform data, first Phase current low-pass filtered waveform data and the first Phase current low-pass filtered waveform data; Step S52: For the second Phase current waveform data, second Phase current waveform data and second The phase current waveform data is low-pass filtered to obtain second low-pass filtered waveform data, the second low-pass filtered waveform data includes a second Phase current low-pass filter waveform data, second Phase current low-pass filtered waveform data and the second Phase current low-pass filtered waveform data; Step S53: selecting first waveform data for matching and comparison from the first low-pass filtered waveform data through a first matching window; Step S54: selecting second waveform data from the second low-pass filtered waveform data through a second matching window to start waveform matching, wherein the time length of the first matching window is the same as that of the second matching window; Step S55: determine whether the first waveform data and the second waveform data meet the waveform matching criterion. If so, execute step S56. If not, determine whether the second waveform data has been traversed. If it is determined that the traversal has been completed, the waveform matching fails and the execution is completed. If it is determined that the traversal has not been completed, move the second matching window, reselect the second waveform data, and continue to return to step S55. Step S56: widening the first matching window, widening the second matching window, and performing waveform matching on the first waveform data selected by the widened first matching window and the second waveform data selected by the widened second matching window; Step S57: determine whether the first waveform data and the second waveform data meet the waveform matching criterion, if so, the matching is completed, if not, execute step S58; Step S58: restore the first matching window and the second matching window to their original sizes, move the second matching window, reselect the second waveform data, and then return to step S55; The waveform matching criteria are as follows: The match is completed if any of the following criteria is met; Criterion I: All three-phase circuits satisfy the waveform matching judgment formula; Criterion II: In a three-phase circuit, any two-phase circuits satisfy the waveform matching judgment formula, and the other phase circuit satisfies: In the formula, represents the correlation coefficient of the waveform selected by the first distributed acquisition module and the second distributed acquisition module for identification, represents the second threshold; The expression of the waveform matching judgment formula is: In the formula, Indicates the size of the first matching window, represents the size of the second matching window, Indicates the number of periodic waves in the waveform data, express Phase circuit, , Indicates the first distributed collection module collects Waveform data of phase circuit, Indicates the first Waveform data of phase circuit, Indicates the first threshold.

2. The ground fault detection method according to claim 1, characterized in that: The calculation formula for the difference operation is: In the formula, waveform data representing first residual current data in the first waveform data after waveform matching, waveform data representing second residual current data in the second waveform data after waveform matching, A differential waveform representing the waveform data of the first residual current data after waveform matching and the waveform data of the second residual current data after waveform matching.

3. The ground fault detection method according to claim 2, characterized in that: The expression of fault criterion is: In the formula, represent The effective value of Indicates the third threshold.

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