Electric shock fault positioning method and device, equipment, storage medium and program product

Abstract

The invention provides an electric shock fault positioning method and device, equipment, a storage medium and a program product. The method comprises the following steps: for each section in the low-voltage power distribution network, obtaining residual current and repeated grounding point current of a plurality of detection points in a first measurement period; for each detection point, extracting a first harmonic amplitude of the residual current and a second harmonic amplitude of the repeated grounding point current; determining the transformation ratio of the detection point according to the first harmonic amplitude, the second harmonic amplitude, a third harmonic amplitude corresponding to the residual current in the second measurement period and a fourth harmonic amplitude corresponding to the repeated grounding point current in the second measurement period; and when the transformation ratio of at least one detection point in the plurality of sections is greater than a transformation ratio threshold value, determining that the low-voltage distribution network has an electric shock fault, and positioning the section, having the electric shock fault, of the low-voltage distribution network according to the transformation ratios of the detection points in the plurality of sections. The method is used for achieving the effect of improving the electric shock fault positioning precision.

Description

Technical Field

[0001] The present application relates to the technical field of electric shock detection, and in particular, to a method, device, equipment, storage medium, and program product for electric shock fault location. Background Art

[0002] The large-scale access of distributed photovoltaic power sources to low-voltage distribution networks has brought unprecedented challenges to traditional leakage protection mechanisms. As a common problem in power systems, timely and accurate detection of electric shock faults is crucial for ensuring personal safety and stable operation of the system.

[0003] Currently, the location of electric shock faults in low-voltage distribution networks mainly relies on the action information of residual current protection devices (RCDs) and the measurement of electrical quantities such as current and voltage. Specifically, when an electric shock fault occurs, the RCD will detect abnormal residual current and trip, cutting off the faulty circuit. Subsequently, maintenance personnel analyze the propagation path and characteristics of the fault current based on the action records of the RCD and the current and voltage data measured on-site. By comparing the data at different measurement points, maintenance personnel can determine the location of the fault and take corresponding repair measures.

[0004] However, the above-mentioned electric shock fault location method has low location accuracy and low reliability. Summary of the Invention

[0005] Embodiments of the present application provide a method, device, equipment, storage medium, and program product for electric shock fault location to achieve the effect of improving the accuracy of electric shock fault location.

[0006] In a first aspect, an embodiment of the present application provides an electric shock fault location method applied to a low-voltage power distribution system for detecting whether an electric shock fault occurs in a low-voltage distribution network and locating the fault; the low-voltage distribution network includes multiple sections, and each section contains multiple detection points; the method includes:

[0007] For each section, obtain the residual current and the current at the repeated grounding point at multiple detection points within a first measurement period;

[0008] For each detection point, extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the current at the repeated grounding point;

[0009] Determine the transformation ratio of the detection point according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within a second measurement period, and the fourth harmonic amplitude corresponding to the current at the repeated grounding point within the second measurement period; the second measurement period is the previous measurement period of the first measurement period;

[0010] When the transformation ratio of at least one detection point in multiple sections is greater than the transformation ratio threshold, it is determined that an electric shock fault has occurred in the low-voltage distribution network, and the section where the electric shock fault occurs in the low-voltage distribution network is located based on the transformation ratios of the detection points in the multiple sections.

[0011] In a possible implementation manner, determining the transformation ratio of the detection point according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within the second measurement period, and the fourth harmonic amplitude corresponding to the repeated grounding point current within the second measurement period includes:

[0012] Calculating a first difference between the first harmonic amplitude and the third harmonic amplitude, and a second difference between the second harmonic amplitude and the fourth harmonic amplitude, and determining the ratio of the absolute value of the first difference to the absolute value of the second difference as the transformation ratio of the detection point.

[0013] In a possible implementation manner, locating the section where the electric shock fault occurs in the low-voltage distribution network based on the transformation ratios of the detection points in the multiple sections includes:

[0014] For each section among the multiple sections, calculating the average value of the transformation ratios of the multiple detection points in the section;

[0015] Determining the section with the largest average transformation ratio as the section where the electric shock fault occurs in the low-voltage distribution network.

[0016] In a possible implementation manner, extracting the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current for each detection point includes:

[0017] For each detection point, when the residual current is greater than the first current threshold and the repeated grounding point current is greater than the second current threshold, extracting the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current.

[0018] In a possible implementation manner, extracting the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current for each detection point includes:

[0019] For each detection point, performing an S-transform on the residual current and the repeated grounding point current respectively to obtain the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current.

[0020] In a possible implementation manner, the method further includes:

[0021] When the transformation ratios of the multiple detection points corresponding to each section in the multiple sections are all less than or equal to the transformation ratio threshold, it is determined that no electric shock fault has occurred in the low-voltage distribution system.

[0022] Second aspect, an electric shock fault location device provided by an embodiment of the present application is applied to a low-voltage power distribution system, and the low-voltage power distribution system is used to detect whether an electric shock fault occurs in a low-voltage power distribution network and locate the fault; the low-voltage power distribution network includes multiple sections, and each section contains multiple detection points; the device includes:

[0023] An acquisition module, configured to obtain the residual current and the repeated grounding point current of multiple detection points within a first measurement period for each section;

[0024] An extraction module, configured to extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current for each detection point;

[0025] A determination module, configured to determine the transformation ratio of the detection point according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within a second measurement period, and the fourth harmonic amplitude corresponding to the repeated grounding point current within the second measurement period; the second measurement period is the previous measurement period of the first measurement period;

[0026] The determination module is further configured to determine that an electric shock fault occurs in the low-voltage power distribution network when the transformation ratio of at least one detection point in multiple sections is greater than a transformation ratio threshold;

[0027] A location module, configured to locate the section where the electric shock fault occurs in the low-voltage power distribution network according to the transformation ratio of the detection points in multiple sections.

[0028] In a possible implementation manner, the determination module is specifically configured to calculate a first difference between the first harmonic amplitude and the third harmonic amplitude, and a second difference between the second harmonic amplitude and the fourth harmonic amplitude, and determine the ratio of the absolute value of the first difference to the absolute value of the second difference as the transformation ratio of the detection point.

[0029] In a possible implementation manner, the location module is specifically configured to calculate the average transformation ratio of multiple detection points in each section for each section among multiple sections;

[0030] Determine the section with the largest average transformation ratio as the section where the electric shock fault occurs in the low-voltage power distribution network.

[0031] In a possible implementation manner, the extraction module is specifically configured to extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current when the residual current is greater than a first current threshold and the repeated grounding point current is greater than a second current threshold for each detection point.

[0032] In a possible implementation manner, the extraction module is specifically configured to perform an S transform on the residual current and the repeated grounding point current respectively for each detection point to obtain the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current.

[0033] In a possible implementation, the determining module is further configured to determine that no electric shock fault occurs in the low-voltage power distribution system when the transformation ratios of the multiple detection points corresponding to each section among the multiple sections are less than or equal to the transformation ratio threshold.

[0034] In a third aspect, an embodiment of the present application provides an electronic device, including: a memory and a processor;

[0035] The memory stores computer-executable instructions;

[0036] The processor executes the computer-executable instructions stored in the memory, so that the processor executes the first aspect and / or various possible implementations of the first aspect as described above.

[0037] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement the first aspect and / or various possible implementations of the first aspect as described above.

[0038] In a fifth aspect, an embodiment of the present application provides a computer program product, including a computer program. When the computer program is executed by a processor, it implements the first aspect and / or various possible implementations of the first aspect as described above.

[0039] The electric shock fault location method, device, equipment, storage medium, and program product provided by the embodiments of the present application detect the residual current and the current of the repeated grounding point of multiple detection points in each section of the low-voltage power distribution network, determine the transformation ratio of the corresponding detection point according to the detected current data, and judge whether an electric shock fault occurs in the low-voltage power distribution network according to the transformation ratios of the multiple detection points in each section, and locate the faulty section when it is determined that an electric shock fault occurs. Compared with the prior art that only uses the residual current to detect electric shock faults, the electric shock fault location method of the present application can effectively reduce the misoperation of the RCD, more accurately detect whether an electric shock fault occurs in the low-voltage power distribution network, and accurately locate the fault location. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0041] Figure 1 FIG. 1 is a schematic structural diagram of a circuit state of a multi-load system with a photovoltaic power source provided by the present application;

[0042] Figure 2 FIG. 2 is a schematic structural diagram of a circuit state of a multi-load system with a photovoltaic power source provided by the present application;

[0043] Figure 3A schematic diagram of three structures of the circuit state of a multi-load system with a photovoltaic power supply provided by this application;

[0044] Figure 4 A schematic diagram of four structures of the circuit state of a multi-load system with a photovoltaic power supply provided by this application;

[0045] Figure 5 A schematic diagram of the process of a method for locating electric shock faults provided by this application;

[0046] Figure 6 A schematic diagram of a simulation model of a multi-feeder system provided by this application;

[0047] Figure 7 A schematic diagram of the structure of a device for locating electric shock faults provided by this application;

[0048] Figure 8 A schematic diagram of the structure of an electronic device provided by this application.

[0049] Through the above-mentioned drawings, the specific embodiments of this application have been shown, and there will be more detailed descriptions hereinafter. These drawings and text descriptions are not intended to limit the scope of the concept of this application in any way, but to illustrate the concept of this application to those skilled in the art by referring to specific embodiments. Detailed Description of the Embodiments

[0050] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. On the contrary, they are only examples of devices and methods consistent with some aspects of this application as detailed in the appended claims.

[0051] With the rapid development of the renewable energy industry, the installed capacity of distributed light sources represented by distributed photovoltaic has expanded rapidly. The large-scale access of distributed photovoltaic power supplies to low-voltage distribution networks not only promotes the optimization of the energy structure and environmental protection, but also poses new challenges to the safety and stability of the power system. On the one hand, the access of distributed photovoltaic power supplies, especially non-isolated photovoltaic systems, is directly electrically connected to the distribution network due to the lack of a transformer, resulting in the common-mode current flowing through the parasitic capacitance being prone to cause frequent false tripping of the RCD. On the other hand, the high proportion of grid-connected inverters brings high-order harmonic pollution with volatility to the low-voltage distribution network, resulting in the complication of the waveform characteristics of the leakage current. In addition, the double-end power supply phenomenon formed after the access of the photovoltaic power supply further increases the technical difficulty of electric shock fault detection and leakage protection.

[0052] At present, the location of electric shock faults in low-voltage distribution networks mainly relies on the action information of RCDs and the measurement of electrical quantities such as current and voltage. When an electric shock fault occurs, the RCD will detect abnormal residual current and trip, cutting off the faulty circuit. Subsequently, the operation and maintenance personnel analyze the propagation path and characteristics of the fault current based on the action records of the RCD and the current and voltage data measured on-site. By comparing the data at different measurement points, the operation and maintenance personnel can determine the location where the fault occurred and take corresponding repair measures. Among them, the traditional AC-type RCD is mainly applicable to the residual current in the form of power frequency sine. When facing the harmonic pollution introduced by distributed photovoltaic systems, it is difficult to ensure normal and accurate operation. In order to improve the applicability of detection, the industry has developed B-type RCDs and magnetic modulation current sensors, which can meet the detection requirements of various complex residual currents including alternating current, direct current, and pulsating direct current. However, these protection devices need to set fixed action thresholds and are easily affected by the common-mode current caused by distributed photovoltaic power sources, resulting in frequent misoperations. In addition, although the Hall sensor type residual current protector has the advantage of a wide detection range, its anti-interference ability is weak and it is easily affected by external magnetic fields and direct current components. In recent years, electric shock fault detection network models based on deep learning algorithms such as backpropagation neural networks and kernel extreme learning machines have also been proposed. However, these model structures are complex, require a large number of data samples, take a long time to train, and the acquisition of data samples is restricted by various conditions such as the photovoltaic access location, access quantity, and geographical location, and do not have universal applicability.

[0053] Based on the above problems, the present application provides a method, device, equipment, storage medium, and program product for electric shock fault location. By detecting the residual current and the current of the repeated grounding point at multiple detection points in each section of the low-voltage distribution network, and according to the detected current data, determining the transformation ratio of the corresponding detection point, and judging whether an electric shock fault occurs in the low-voltage distribution network based on the transformation ratios of multiple detection points in each section, and locating the faulty section when it is determined that an electric shock fault has occurred. Compared with the prior art that only uses residual current to detect electric shock faults, the electric shock fault location method of the present application can effectively reduce the misoperation of RCDs, more accurately detect whether an electric shock fault occurs in the low-voltage distribution network, and accurately locate the fault location.

[0054] The following will specifically describe the technical solutions of the present application and how the technical solutions of the present application solve the above technical problems with specific embodiments. These specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below with reference to the accompanying drawings.

[0055] Figure 1-4 It is a schematic structural diagram of different states of a multi-load system circuit with a photovoltaic power source provided by the present application. As Figure 1-4As shown in the figure, in a low-voltage distribution network, the unbalanced three-phase current caused by load imbalance flows into the ground through the neutral line impedance, the transformer neutral point, and the repeated grounding points. Normal ground leakage currents also occur in the three-phase lines and loads. In a non-isolated distributed photovoltaic three-phase grid-connected system, the inverter outputs a varying common-mode voltage, thereby forming a common-mode current in the loop composed of the parasitic capacitance between the photovoltaic power supply and the ground, the inverter, the filter, and the low-voltage distribution network. Therefore, the unbalanced three-phase current, the ground leakage current, and the common-mode current are inherent components during the normal operation of the system.

[0056] In a TN-C-S system, multiple loads are usually connected to one feeder, and repeated grounding is carried out at each load. Figure 1-4 Among them, Z Load1 (including Z ALoad1 , Z BLoad1 , Z CLoad1 ) is the load 1, Z Load2 (including Z ALoad2 , Z BLoad2 , Z CLoad2 ) is the load 2, Z AG1 , Z BG1 , Z CG1 , Z AG2 , Z BG2 , Z CG2 is the line-to-ground leakage impedance, Z SG1 , Z SG2 is the repeated grounding point impedance, Z NLine1 , Z NLine2 is the neutral line impedance, Z ALine1 , Z BLine1 , Z CLine1 , Z ALine2 , Z BLine2 , Z CLine2 , Z ALine3 , Z BLine3 , Z CLine3 is the three-phase line impedance, Z h1 , Z h2 is the body touch resistance impedance, C PV is the parasitic capacitance between the photovoltaic and the ground.

[0057] In a 10 / 0.4 kV TN-C-S system, after the three-phase power supply is grounded at the neutral point O of the transformer, the Protective Earth and Neutral (PEN) line is divided into a protective earth line (PE line) and a neutral line (N line) on the user side. During normal operation, unbalanced three-phase currents are generated due to the asymmetrical operation of Load 1 and Load 2, flowing through the three-phase line impedance and the zero-line impedance in sequence, and finally flowing into the earth through the neutral point O of the transformer and the impedance of the repeated grounding point. The ground leakage current caused by the line-to-earth leakage impedance flows into the earth through the neutral point O of the transformer. The common-mode current of the non-isolated photovoltaic system is generated by the high-frequency switching action of the inverter, forming a loop through the filtering device, DC / AC converter, boost circuit, and the parasitic capacitance between the photovoltaic array and the earth, and finally flowing into the earth through the parasitic capacitance and the neutral point O of the transformer. RCD1 and RCD2 monitor the residual currents of the branches of Load 1 and Load 2 respectively to ensure that the unbalanced three-phase currents, ground leakage currents, and common-mode currents are within a safe range.

[0058] Taking two loads as an example for analysis, Figure 1 The dotted line in [Figure] is the flow path of the unbalanced three-phase current in Load 1 and the solid line is the flow path of the unbalanced three-phase current in Load 2. Figure 2 The two-dot chain line in [Figure] is the flow path of the unbalanced three-phase current in Load 2 and the solid line is the flow path of the unbalanced three-phase current in Load 1. Figure 3 The center dotted line is the flow path of the electric shock current when the electric shock fault occurs between the transformer and Load 1 and the semi-dotted line is the flow path of the electric shock current when the electric shock fault occurs between Load 1 and Load 2. Figure 4 For Load 1, the unbalanced three-phase current flows back to the neutral point of the transformer through Path 1 (

[0059] ), Path 2 ( ), and Path 3 ( ), ), ), and Path 3 ( ), ), ), then the current flowing through the repeated grounding impedance is:

[0060] (1)

[0061] where is the impedance between the neutral point of the 10 / 0.4 kV transformer and the earth, is the repeated grounding impedance set at Load 1, is the repeated grounding impedance set at Load 2, , are the three-phase line and zero-line impedances.

[0062] Three-phase normal ground leakage current The expression is:

[0063] (2)

[0064] In the formula, 、 、 are the normal ground leakage currents of phases A, B, and C, 、 、 are the ground leakage impedances of the line and the load equipment respectively.

[0065] Common-mode current The expression is:

[0066] (3)

[0067] In the formula, is the parasitic capacitance of the photovoltaic power supply to the ground, is the common-mode voltage generated on the parasitic capacitance.

[0068] Due to the ground leakage impedances 、 、 reaching values of several thousand ohms and above, far exceeding 、 、 Therefore, when analyzing the three-phase unbalanced current and the electric shock current , the influence of 、 、 is ignored, and 、 、 is transformed to obtain:

[0069] (4)

[0070] (5)

[0071] (6)

[0072] For load 2, the current flowing through the repeated grounding impedance is:

[0073] (7)

[0074] When an electric shock fault occurs, the residual current is:

[0075] (8)

[0076] Wherein, is the leakage current of the unbalanced three-phase current flowing into the ground through the repeated grounding point, is the normal three-phase ground leakage current, is the common-mode current when the photovoltaic equipment is leaking electricity, is the electric shock current when an electric shock fault occurs, , , are the sudden change amounts of each current.

[0077] When an electric shock fault occurs between load 1 and load 2 ( Figure 4 ), the residual current flowing through between the transformer and load 1 is:

[0078] (9)

[0079] Wherein,

[0080]

[0081]

[0082]

[0083] The residual current flowing through between load 1 and load 2 is:

[0084] (10)

[0085] Wherein, the electric shock current coefficient in is , the electric shock current coefficient in is , and it is calculated that:

[0086] (11)

[0087] In the low-voltage distribution network, since the line length is generally between dozens of meters and hundreds of meters, the zero-line impedance is generally at the order of magnitude below 0.1 , is generally not higher than 4 , is generally not higher than 10 , so is much smaller than , and thus the coefficient is obtained.

[0088] When the electric shock fault occurs between the transformer and load 1 ( Figure 3 ), the residual current flowing between the transformer and load 1 for:

[0089] (12)

[0090] Residual current flowing between load 1 and load 2 for:

[0091] (13)

[0092] in, The electric shock current coefficient is , Medium shock current coefficient , the coefficient can be derived .

[0093] When an electric shock fault occurs, the electric shock current in the section corresponding to the fault point The coefficient of Due to the repeated grounding point shunting, the current is reduced successively, so each section can be The size of the mutation is analyzed to determine the location of the electric shock fault, thereby locating the fault.

[0094] This application defines the transformation ratio M as the residual current harmonic change The harmonic change of the current at the repeated grounding point The absolute value of the ratio of , n represents the harmonic order.

[0095] The system operates normally and the load switching time ratio is for:

[0096] (14)

[0097] When an electric shock fault occurs, the ratio for:

[0098] (15)

[0099] When the system is operating normally, calculate the transformation ratio caused by load switching , and accordingly set the transformation ratio threshold corresponding to the nth harmonic When an electric shock occurs, Increase variable, Mutations occur, calculated in real time Value greater than threshold , thereby determining that an electric shock fault has occurred.

[0100] Figure 5 It is a schematic flowchart of a method for locating electric shock faults provided for this application. In this embodiment, the electric shock fault location method is applied to a low-voltage power distribution system, which is used to detect whether an electric shock fault occurs in the low-voltage power distribution network and locate the fault. The low-voltage power distribution network includes multiple sections, and each section contains multiple detection points. As Figure 5 shown, taking the low-voltage power distribution system as the execution subject, the method includes:

[0101] S101. For each section, obtain the residual current and the current at the repeated grounding point of multiple detection points within the first measurement period.

[0102] In this embodiment, the sections are divided according to the load. For example Figure 1 the repeated grounding point and the repeated grounding point only contain Load 2 in between, which is one section.

[0103] The low-voltage power distribution system conducts electric shock fault detection and fault location for the low-voltage power distribution network with distributed photovoltaic multi-point access. Specifically, the low-voltage power distribution system collects the current flowing through the repeated grounding point and the current flowing through the RCD of the three-phase unbalanced current according to a preset measurement period, and obtains the current at the repeated grounding point and the residual current.

[0104] S102. For each detection point, extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the current at the repeated grounding point.

[0105] In this embodiment, the low-voltage power distribution system can process the residual current and the current at the repeated grounding point respectively through a harmonic analysis algorithm, extract the harmonic components in the current, and obtain the first harmonic amplitude and the second harmonic amplitude.

[0106] S103. Determine the transformation ratio of the detection point according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within the second measurement period, and the fourth harmonic amplitude corresponding to the current at the repeated grounding point within the second measurement period.

[0107] Wherein, the second measurement period is the previous measurement period of the first measurement period.

[0108] In this embodiment, the low-voltage power distribution system can obtain the harmonic amplitudes of the residual current and the current at the repeated grounding point within the second measurement period from the storage module, and calculate the absolute value of the ratio of the change in harmonic amplitudes between the two measurement periods.

[0109] S104. When the transformation ratio at at least one detection point in multiple sections is greater than the transformation ratio threshold, it is determined that an electric shock fault has occurred in the low-voltage distribution network, and the section where the electric shock fault occurs in the low-voltage distribution network is located based on the transformation ratios of the detection points in the multiple sections.

[0110] In this embodiment, the low-voltage power distribution system can input the transformation ratio into the fault detection algorithm, and the algorithm determines whether an electric shock fault has occurred in the low-voltage distribution network according to the value of the transformation ratio in combination with the preset safety standards.

[0111] When the transformation ratio of one detection point in multiple sections is greater than the transformation ratio threshold, it indicates that an electric shock fault has occurred in the low-voltage distribution network. Moreover, when faults occur in different sections, the transformation ratios of each detection point are different. Therefore, according to the transformation ratios of each detection point, it can be determined which section has the fault.

[0112] In this embodiment, the transformation ratio threshold is determined according to the transformation ratio generated by the load switching during the normal operation of the low-voltage distribution network.

[0113] Threshold is related to the topological structure of the photovoltaic power supply and load access in the substation area. Therefore, the corresponding threshold can be set according to the actual system topology, line parameters, and environmental conditions. .

[0114] If an electric shock fault is detected, the electric shock detection system can send an alarm to the operator through the user interface, alarm module, or other communication methods, and may trigger automatic power-off or other safety measures.

[0115] The electric shock fault location method provided in this embodiment realizes the high-sensitivity detection and accurate judgment of the electric shock fault in the low-voltage distribution network through steps such as extracting the harmonic amplitude, calculating the transformation ratio, and judging the fault status, and locates the section where the fault occurs by comprehensively considering the transformation ratios of each detection point. This method provides a strong guarantee for the safe operation of the low-voltage distribution network.

[0116] In a possible implementation manner, for each detection point, when the residual current is greater than the first current threshold and the current at the repeated grounding point is greater than the second current threshold, the low-voltage power distribution system can extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the current at the repeated grounding point.

[0117] Specifically, due to factors such as sampling resolution and environmental noise during the actual operation of the power system, the sudden change in the residual current and the sudden change in the current at the repeated grounding point collected by the electric shock detection system must contain measurement errors, and when and are smaller, the influence of the measurement error on the transformation ratio is greater.

[0118] Therefore, it is necessary to set effective measurement thresholds for the residual current and the current at the repeated earthing point. and When is greater than the threshold and is greater than the threshold then, by extracting the harmonic amplitude and calculating the transformation ratio, the detection accuracy of the electric shock fault can be further improved.

[0119] Compared with only using the current threshold in the prior art, in this embodiment, a dual combination criterion is also formed by combining the transformation ratio threshold. When the line current flows through the RCD, if the threshold conditions under this dual combination criterion of the current threshold and the transformation ratio threshold are met, the RCD will act to disconnect the line. When there is a leakage in the photovoltaic power supply or the load switching causes a large residual current in the substation area, the residual current and the current at the repeated earthing point will exceed the operating setting value. However, when the transformation ratio criterion is not met, the RCD will not act to disconnect the line, thereby effectively reducing the misoperation of the RCD. In addition, the fault section can be located within multiple sections according to the transformation ratios of multiple detection points in multiple sections. In summary, the method of this embodiment can not only avoid the misoperation caused by load switching, accurately judge the electric shock fault, but also locate the fault section.

[0120] Based on the above embodiment, the present application constructs a simulation model of a 400V low-voltage distribution network with distributed photovoltaic access based on the three-layer topology relationship of the substation area - line - user and the distribution characteristics of the residual current in the substation area, and selects the human equivalent circuit model of Freiberg as the human electric shock simulation model, as Figure 6 shown.

[0121] This model is used to simulate the electric shock characteristics of a distribution network with distributed photovoltaic in a 10 / 0.4kV TN-C-S system. The low-voltage distribution network steps down 10kV to 0.4kV through a transformer T and connects to the bus, connecting three feeders (feeder 1 - 3) and eight load nodes (L1 - L8). Among them, distributed photovoltaics PV1 and PV2 are directly connected to the bus, and PV3, PV4, and PV5 are respectively connected between the nodes of L2 - L3, L6 - L7, and L8 - L1. This model considers parameters such as line impedance, load impedance, ground leakage impedance, repeated earthing impedance, and photovoltaic parasitic capacitance. By setting the impedance of the biological body contact, it simulates the human body contact scenario, is used to study the electric shock current characteristics under different photovoltaic penetration rates, three-phase unbalance degrees and other working conditions, evaluate the protection performance of the RCD, and provide data support for the safe design of the distribution network and the photovoltaic grid connection protection.

[0122] Combined with the above model, the residual current and the current at the repeated earthing point during normal operation of the substation area can be obtained.

[0123] The residual current can be extracted based on the S - transform. and the harmonic amplitude of the repeated grounding point current of the harmonic amplitude.

[0124] In a possible implementation manner, the specific implementation of step S102 includes: for each detection point, perform the S - transform on the residual current and the repeated grounding point current respectively, to obtain the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current.

[0125] Specifically, the feature extraction process of the current in the S - transform is as follows:

[0126] (16)

[0127] (17)

[0128] (18)

[0129] In the formula, is the collected electric shock current signal; is the Gaussian window function; is the time - shift factor, used to characterize the position of the control window on the time axis; is the variance of the Gaussian function, which is a time - varying parameter with respect to t.

[0130] is the time - frequency spectrum matrix obtained through the transformation, which characterizes the change of the frequency components of the electric shock signal from low - frequency to high - frequency over time. The Fourier spectrum form is:

[0131] (19)

[0132] In the formula, .

[0133] Accordingly, the expression form of the discrete current signal is:

[0134] (20)

[0135] In the formula, k is the discrete time point, T is the sampling time interval, N is the length of the discrete signal, .

[0136] Let , , finally, the S - transform of the discrete signal can be expressed as:

[0137] (21)

[0138] In the formula, n≠0 represents the number of rows in the spectrum matrix, and m is the number of columns.

[0139] Define the harmonic amplitude functions of the modulus time-frequency matrix as and respectively. This function represents the variation of the corresponding harmonic amplitude with time in the modulus time-frequency matrix after the S-transform, from which the harmonic amplitudes of the residual current and the harmonic amplitudes of the current at the repeated grounding point are obtained.

[0140] (22)

[0141] (23)

[0142] where t is the sampling time, and are the modulus time-frequency matrices after the S-transform corresponding to the residual current and the current at the repeated grounding point respectively. Among them, the rows of the matrix correspond to frequencies and the columns correspond to time.

[0143] Furthermore, the expression of the transformation ratio is:

[0144] (24)

[0145] where n is an integer from 2 to 5, representing the harmonic order.

[0146] Compared with the short-time Fourier transform, the S-transform can adaptively adjust the height and width of the Gaussian window according to the frequency change and provide intuitive time-frequency characteristics. Compared with the wavelet transform, the S-transform can not only adjust the time width but also its inverse transform is lossless and reversible. The S-transform is used for the analysis of the harmonic characteristics of the electric shock current, which can determine the harmonic amplitudes of each order of the electric shock current and can also compare the time-frequency characteristics before and after the electric shock.

[0147] In this embodiment, the S-transform can accurately extract the harmonic amplitude information in the residual current and the current at the repeated grounding point. By extracting the harmonic amplitude information, the electric shock detection system can achieve high-sensitivity detection and accurate judgment of the electric shock fault, improve the robustness of the electric shock fault detection, and provide a strong guarantee for the safe operation of the power system.

[0148] On this basis, the specific implementation manner of step S103 includes calculating the first difference between the first harmonic amplitude and the third harmonic amplitude, and the second difference between the second harmonic amplitude and the fourth harmonic amplitude, and determining the ratio of the absolute value of the first difference to the absolute value of the second difference as the transformation ratio of the detection point.

[0149] It can be understood that the first difference is , the second difference is , and the expression of the transformation ratio is as shown in formula (24).

[0150] In a possible implementation, in step S104, according to the transformation ratios of the detection points in multiple sections, the section where an electric shock fault occurs in the low-voltage distribution network is located among the multiple sections. The specific implementation method includes:

[0151] S1041. For each section among the multiple sections, calculate the average value of the transformation ratios of multiple detection points in the section.

[0152] It can be understood that each section contains multiple detection points, and the determination method of the transformation ratio of each detection point is similar to the specific implementation method of step S103 in the Figure 5 embodiment, and will not be elaborated here.

[0153] According to the transformation ratios of multiple detection points in each section, calculate the average value, which is the transformation ratio of this section.

[0154] S1042. Determine the section with the largest average transformation ratio as the section where an electric shock fault occurs in the low-voltage distribution network.

[0155] Determine the section where an electric shock fault occurs according to the transformation ratio of each section. Specifically, when an electric shock fault occurs, the coefficient of the electric shock current in the section corresponding to the fault point is the largest, that is, the magnitude of the mutation amount is the largest, and the current flowing through other sections decreases successively due to the shunt of the repeated grounding points. Therefore, the magnitude of the mutation amount of each section can be analyzed to determine the location of the electric shock fault, so as to perform fault location.

[0156] It can be understood that the low-voltage distribution system can also determine that no electric shock fault has occurred in the low-voltage distribution system when the transformation ratios of multiple detection points corresponding to each section in multiple sections are all less than or equal to the transformation ratio threshold.

[0157] Specifically, when the harmonic order n of the harmonic amplitude is different, the transformation ratio threshold is different. For each section, if the transformation ratios of multiple detection points are all less than the transformation ratio threshold, it indicates that there is no electric shock fault current in the change amount of the residual current, that is, no electric shock fault has occurred in the low-voltage distribution network.

[0158] Figure 7 It is a schematic structural diagram of an electric shock fault location device provided by the present application. As Figure 7 shown, the electric shock fault location device 10 in this embodiment is used to implement the operations corresponding to the low-voltage distribution system in any of the above method embodiments. The electric shock fault location device 10 provided in this embodiment is used to detect whether an electric shock fault occurs in the low-voltage distribution network and locate the fault; the low-voltage distribution network includes multiple sections, and each section contains multiple detection points; the electric shock fault location device 10 includes:

[0159] An acquisition module 11, configured to acquire the residual current and the repeated grounding point current of multiple detection points within a first measurement period for each section;

[0160] An extraction module 12 is configured to extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current for each detection point.

[0161] A determination module 13 is configured to determine the transformation ratio of the detection point according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within the second measurement period, and the fourth harmonic amplitude corresponding to the repeated grounding point current within the second measurement period; the second measurement period is the previous measurement period of the first measurement period.

[0162] The determination module 13 is further configured to determine that an electric shock fault has occurred in the low-voltage distribution network when the transformation ratio of at least one detection point in multiple sections is greater than the transformation ratio threshold.

[0163] A positioning module 14 is configured to locate the section where the electric shock fault occurs in the low-voltage distribution network according to the transformation ratios of the detection points in multiple sections.

[0164] In a possible implementation manner, the determination module 13 is specifically configured to calculate a first difference between the first harmonic amplitude and the third harmonic amplitude, and a second difference between the second harmonic amplitude and the fourth harmonic amplitude, and determine the ratio of the absolute value of the first difference to the absolute value of the second difference as the transformation ratio of the detection point.

[0165] In a possible implementation manner, the positioning module 14 is specifically configured to calculate the average transformation ratio of multiple detection points in each section for each of the multiple sections.

[0166] Determine the section with the largest average transformation ratio as the section where the electric shock fault occurs in the low-voltage distribution network.

[0167] In a possible implementation manner, the extraction module 12 is specifically configured to extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current for each detection point when the residual current is greater than the first current threshold and the repeated grounding point current is greater than the second current threshold.

[0168] In a possible implementation manner, the extraction module 12 is specifically configured to perform an S transform on the residual current and the repeated grounding point current respectively for each detection point to obtain the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current.

[0169] In a possible implementation manner, the determination module 13 is further configured to determine that no electric shock fault has occurred in the low-voltage distribution system when the transformation ratios of multiple detection points corresponding to each section in multiple sections are all less than or equal to the transformation ratio threshold.

[0170] The electric shock fault positioning device 10 provided in this embodiment can execute the method provided in the above method embodiment, and its implementation principle and technical effects are similar, which will not be elaborated here in this embodiment.

[0171] Figure 8 A structural schematic diagram of an electronic device provided for this application. As Figure 8 shown, the electronic device 20 provided in this embodiment includes: a memory 21 and at least one processor 22. Optionally, the device 20 further includes a communication component 23. Among them, the memory 21, the processor 22, and the communication component 23 are connected through a bus 24.

[0172] In a specific implementation process, at least one processor 22 executes computer execution instructions stored in the memory 21, so that at least one processor 22 executes the above method.

[0173] For the specific implementation process of the processor 22, reference can be made to the above method embodiment. The implementation principle and technical effect are similar, and will not be elaborated here in this embodiment.

[0174] In the above embodiment, it should be understood that the processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The steps of the method disclosed in combination with the invention can be directly embodied as being executed by a hardware processor, or executed by a combination of hardware and software modules in the processor.

[0175] The memory may include a high-speed memory (Random Access Memory, RAM), and may also include a non-volatile memory (Non-volatile Memory, NVM), such as at least one disk memory.

[0176] The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For the convenience of representation, the bus in the drawings of this application is not limited to only one bus or one type of bus.

[0177] This application also provides a computer program product, including a computer program, which implements the above method when executed by a processor.

[0178] The present application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above method.

[0179] The above-readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, a magnetic disk, or an optical disk. The readable storage medium can be any available medium accessible by a general-purpose or special-purpose computer.

[0180] An exemplary readable storage medium is coupled to the processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can be located in an application-specific integrated circuit (ASIC). Of course, the processor and the readable storage medium can also exist as discrete components in a device.

[0181] The division of units is merely a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection between each other can be an indirect coupling or communication connection through some interfaces, devices, or units, and can be in electrical, mechanical, or other forms.

[0182] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0183] In addition, in each embodiment of the present invention, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit.

[0184] If a function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of various embodiments of the present invention. The aforementioned storage medium includes: USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs, etc., all kinds of media that can store program codes.

[0185] Those of ordinary skill in the art can understand that all or part of the steps of implementing the above method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When this program is executed, it executes the steps including the above method embodiments; and the aforementioned storage medium includes: ROMs, RAMs, magnetic disks, or optical discs, etc., all kinds of media that can store program codes.

[0186] Finally, it should be noted that: After considering the specification and practicing the invention disclosed herein, those skilled in the art will easily think of other implementation manners of the present invention. The present invention is intended to cover any variations, uses, or adaptations of the present invention, which follow the general principles of the present invention and include the common general knowledge or conventional technical means in the technical field not disclosed in the present invention. It is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A method for locating an electric shock fault, characterized in that, Applied to a low-voltage power distribution system, the low-voltage power distribution system is used to detect whether an electric shock fault occurs in the low-voltage power distribution network and locate the fault; the low-voltage power distribution network includes multiple sections, and each section contains multiple detection points; the method includes: For each section, obtain the residual current and the repetitive grounding point current of multiple detection points within the first measurement period; For each detection point, extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repetitive grounding point current; Determine the transformation ratio of the detection point according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within the second measurement period, and the fourth harmonic amplitude corresponding to the repetitive grounding point current within the second measurement period; the second measurement period is the previous measurement period of the first measurement period; When the transformation ratio of at least one of the detection points in the multiple sections is greater than the transformation ratio threshold, determine that an electric shock fault has occurred in the low-voltage power distribution network, and locate the section where the electric shock fault occurs in the low-voltage power distribution network according to the transformation ratio of the detection points in the multiple sections.

2. The method according to claim 1, characterized in that, Determine the transformation ratio of the detection point according to the first harmonic amplitude, the second harmonic amplitude, the third harmonic amplitude corresponding to the residual current within the second measurement period, and the fourth harmonic amplitude corresponding to the repetitive grounding point current within the second measurement period, including: Calculate the first difference between the first harmonic amplitude and the third harmonic amplitude, and the second difference between the second harmonic amplitude and the fourth harmonic amplitude, and determine the ratio of the absolute value of the first difference to the absolute value of the second difference as the transformation ratio of the detection point.

3. The method according to claim 1, wherein Locate the section where the electric shock fault occurs in the low-voltage power distribution network according to the transformation ratio of the detection points in the multiple sections, including: For each section in the multiple sections, calculate the average transformation ratio of the multiple detection points in the section; Determine the section with the largest average transformation ratio as the section where the electric shock fault occurs in the low-voltage power distribution network.

4. The method according to claim 1, wherein For each detection point, extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repetitive grounding point current, including: For each detection point, when the residual current is greater than the first current threshold and the repetitive grounding point current is greater than the second current threshold, extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repetitive grounding point current.

5. The method according to claim 1, wherein For each detection point, extract the first harmonic amplitude of the residual current and the second harmonic amplitude of the repetitive grounding point current, including: For each detection point, perform an S transform on the residual current and the repetitive grounding point current respectively to obtain the first harmonic amplitude of the residual current and the second harmonic amplitude of the repetitive grounding point current.

6. The method according to any one of claims 1-5, characterized in that, The method further includes: When the transformation ratios of the multiple detection points corresponding to each section in the multiple sections are all less than or equal to the transformation ratio threshold, determine that no electric shock fault has occurred in the low-voltage power distribution system.

7. An electric shock fault location device, characterized in that, Applied to a low-voltage power distribution system, the low-voltage power distribution system is used to detect whether an electric shock fault occurs in the low-voltage power distribution network and locate the fault; the low-voltage power distribution network includes multiple sections, and each section contains multiple detection points; the device includes: An acquisition module, configured to acquire, for each section, the residual current and the repeated grounding point current of multiple detection points within a first measurement period; An extraction module, configured to extract, for each detection point, the first harmonic amplitude of the residual current and the second harmonic amplitude of the repeated grounding point current; A determination module, configured to determine a transformation ratio of the detection point according to the first harmonic amplitude, the second harmonic amplitude, a third harmonic amplitude corresponding to the residual current within a second measurement period, and a fourth harmonic amplitude corresponding to the repeated grounding point current within the second measurement period; the second measurement period is the previous measurement period of the first measurement period; The determination module is further configured to determine that an electric shock fault occurs in the low-voltage distribution network when the transformation ratio of at least one of the detection points in the multiple sections is greater than a transformation ratio threshold; A positioning module, configured to locate, among the multiple sections, a section where the electric shock fault occurs in the low-voltage distribution network according to the transformation ratios of the detection points in the multiple sections.

8. An electronic device, characterized in that, Comprising: A memory and a processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory, so that the processor executes the method according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, Computer-executable instructions are stored in the computer-readable storage medium, and when the computer-executable instructions are executed by a processor, they are used to implement the method according to any one of claims 1-6.

10. A computer program product, characterized in that, Comprising a computer program, which when executed by a processor implements the method according to any one of claims 1-6.

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