Small current grounding system single-phase grounding fault section positioning method and system

Abstract

The application belongs to the technical field of single-phase grounding fault positioning of distribution network, and particularly discloses a small-current grounding system single-phase grounding fault section positioning method and system; the method comprises the following steps: determining whether to start the detection of single-phase grounding fault section positioning based on the abrupt variables of zero sequence voltage and zero sequence current at the outlet of the protected section; if the detection is started, the outlet of each section of the small-current grounding system respectively calculates the transient zero sequence power of each section; the integral time window is determined by using the zero-crossing detection and continuity checking mechanism, the transient zero sequence power is integrated in the corresponding time window to obtain the generalized transient zero sequence energy; whether the fault point is located upstream or downstream of the current measurement point is judged based on the positive and negative of the generalized transient zero sequence energy at the outlet of the protected section, and whether the section between the two measurement points is the fault section is further judged. The application maximizes the polarity difference of the generalized transient zero sequence energy of the fault section and the non-fault section, and is not affected by the transition resistance and line change.

Description

Technical Field

[0001] This invention relates to the field of single-phase grounding fault location technology in power distribution networks, and in particular to a method and system for locating single-phase grounding fault sections in low-current grounding systems. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Low- and medium-voltage distribution networks widely use low-current grounding methods. While this method allows the system to operate with a fault for a period of time, prolonged fault persistence can lead to more serious accidents such as phase-to-phase short circuits, severely threatening the safe and stable operation of the power system. Therefore, rapid and accurate section location of single-phase grounding faults in low-current grounding systems is particularly important.

[0004] For locating single-phase grounding faults in low-current grounding systems, existing technologies mostly employ line selection and location methods based on transient current or zero-sequence current. However, these methods are easily affected by the compensation characteristics of the arc suppression coil and line changes.

[0005] Existing technologies also disclose methods for fault location using transient energy or power integration. These methods mostly employ empirical fixed time windows for integration calculations. However, transient zero-sequence power is dynamically affected by the fault initial phase angle, system parameters, and the degree of arc suppression coil compensation. Fixed time windows lack theoretical rigor, cannot adapt to different fault scenarios, and are prone to location failure due to integration exceeding limits. Although some methods introduce complex algorithms such as wavelet packet transform to filter frequency bands, their computational load is large and complex, making them difficult to implement in protection devices in engineering fields. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a method and system for locating single-phase grounding fault sections in low-current grounding systems. It utilizes a zero-crossing detection and continuity verification mechanism to adaptively determine the optimal time window for integrating transient zero-sequence power, maximizing the positive and negative differences in generalized transient zero-sequence energy between the faulty and non-faulty sections. The positive and negative polarities of local and adjacent transient zero-sequence energy are then used to locate the faulty section. The calculation process employs multiple electrical quantities at different locations, improving the reliability and sensitivity of the location method.

[0007] In some implementations, the following technical solutions are adopted:

[0008] A method for locating a single-phase grounding fault section in a low-current grounding system includes:

[0009] Based on the abrupt changes in zero-sequence voltage and zero-sequence current at the outlet of the protected section, determine whether to initiate detection for locating a single-phase grounding fault section.

[0010] If detection is initiated, the transient zero-sequence power of each section outlet of the low-current grounding system is calculated separately.

[0011] The integration time window is determined by using zero-crossing detection and continuity verification mechanisms, and the generalized transient zero-sequence energy is obtained by integrating the transient zero-sequence power within the corresponding time window.

[0012] Based on the sign of the generalized transient zero-sequence energy at the exit of the protected section, determine whether the fault point is upstream or downstream of the current measurement point. If the fault point is upstream of the current measurement point, compare the sign of the generalized transient zero-sequence energy values ​​corresponding to the current measurement point and the measurement points of the adjacent upstream section to determine whether the section between the two measurement points is the fault section.

[0013] As a further option, based on the abrupt changes in zero-sequence voltage and zero-sequence current at the outlet of the protected section, it is determined whether to initiate detection for locating single-phase grounding fault sections. Specifically:

[0014] Calculate the difference between the current zero-sequence voltage and zero-sequence current sample values ​​and the corresponding sample values ​​of the previous cycle;

[0015] If the absolute value of the zero-sequence voltage difference corresponding to n consecutive sampling points exceeds the preset setting threshold, and / or the absolute value of the zero-sequence current difference corresponding to n consecutive sampling points exceeds the preset setting threshold, then the detection of single-phase grounding fault section location is initiated, and the fault initiation point is recorded.

[0016] As a further solution, the integration time window is determined using a zero-crossing detection and continuity check mechanism, specifically:

[0017] Based on the zero-crossing detection and continuity verification mechanism of transient zero-sequence power, if the zero-crossing time point is determined, the integral time window is from the fault start point to the zero-crossing time point; if the zero-crossing time point cannot be determined, the integral time window is a fixed time window starting from the fault start point.

[0018] As a further solution, a zero-crossing detection and continuity verification mechanism based on transient zero-sequence power is specifically proposed as follows:

[0019] Determine if the following conditions are met:

[0020] At the (s-1)th sampling point, the zero-sequence power of the segment is negative; at the next s-th sampling point, the zero-sequence power of the segment becomes non-negative.

[0021] Furthermore, starting from sampling point s, until... End of continuous Δ n All sampling points satisfy the condition that the zero-sequence power is greater than zero; among them, Δ n The length of the verification window;

[0022] If satisfied, then sampling point s is the zero-crossing point of the transient zero-sequence power.

[0023] As a further solution, the sign of the generalized transient zero-sequence energy at the exit of the protected section is used to determine whether the fault point is upstream or downstream of the current measurement point. Specifically:

[0024] If the generalized transient zero-sequence energy at the exit of the protected section is positive, the fault point is determined to be upstream of the current section exit measurement point; if the generalized transient zero-sequence energy at the exit of the protected section is negative, the fault point is determined to be downstream of the current section exit measurement point.

[0025] As a further solution, if the fault point is located upstream of the current measurement point, the positive and negative relationships of the generalized transient zero-sequence energy values ​​corresponding to the current measurement point and the upstream adjacent section measurement points are compared to determine whether the section between the two measurement points is a fault section. Specifically:

[0026] If the positive and negative polarities of the generalized transient zero-sequence energy at the outlet measurement points of two adjacent sections are opposite, then the section between the two measurement points is determined to be a fault section.

[0027] If the generalized transient zero-sequence energy at the exit measurement points of two adjacent sections is positive, then the section between the two measurement points is determined to be a non-fault section.

[0028] As a further solution, if the protected section is the last section, then the sign of the generalized transient zero-sequence energy at the measurement point at the exit of the protected section is used to determine whether the last section is a fault section; the specific judgment logic is as follows:

[0029] If the generalized transient zero-sequence energy at the exit measurement point of the protected section is negative, then the protected section is determined to be a fault section.

[0030] If the generalized transient zero-sequence energy at the exit measurement point of the protected section is positive, then the protected section is determined to be a non-fault section.

[0031] In other embodiments, the following technical solutions are adopted:

[0032] A single-phase grounding fault location system for a low-current grounding system, comprising:

[0033] The fault detection module is used to determine whether to initiate the detection of single-phase grounding fault section location based on the abrupt changes in zero-sequence voltage and zero-sequence current at the outlet of the protected section.

[0034] The transient zero-sequence power calculation module is used to calculate the transient zero-sequence power of each section outlet of the low-current grounding system after the start detection.

[0035] The transient zero-sequence energy calculation module is used to determine the integration time window using zero-crossing detection and continuity verification mechanisms, and to integrate the transient zero-sequence power within the corresponding time window to obtain the generalized transient zero-sequence energy.

[0036] The fault location module is used to determine whether the fault point is upstream or downstream of the current measurement point based on the sign of the generalized transient zero-sequence energy at the exit of the protected section. If the fault point is upstream of the current measurement point, the module compares the sign of the generalized transient zero-sequence energy values ​​corresponding to the current measurement point and the measurement points of the adjacent upstream section to determine whether the section between the two measurement points is the fault section.

[0037] In other embodiments, the following technical solutions are adopted:

[0038] A terminal device includes a processor and a memory, the processor being used to implement instructions; the memory being used to store multiple instructions, the instructions being adapted to be loaded by the processor and executed as described above for locating single-phase grounding fault sections in a low-current grounding system.

[0039] In other embodiments, the following technical solutions are adopted:

[0040] A computer-readable storage medium storing a plurality of instructions adapted for loading and execution by a processor of a terminal device of the above-described method for locating single-phase ground fault sections in a low-current grounding system.

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] This invention utilizes zero-crossing detection and continuity verification to adaptively determine the optimal integration window, cleverly avoiding interference from the transient zero-sequence power polarity reversal phenomenon. It unifies the section location criteria for neutral-point ungrounded systems and resonant grounded systems, maximizes the polarity difference of generalized transient zero-sequence energy between faulty and non-faulty sections, and is unaffected by transition resistance and line changes, resulting in high reliability.

[0043] When performing segment location, this invention uses a downstream-to-upstream approach to achieve information exchange, and only requires information from downstream measurement points with negative generalized transient zero-sequence energy. Compared with centralized methods using a single master station or distributed peer-to-peer communication based on measurement points along the entire line, this method has lower communication pressure and faster location speed. At the same time, the fault segment location process does not require data synchronization, which reduces technical requirements.

[0044] Other features and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0045] Figure 1This is a flowchart of the method for locating a single-phase grounding fault section in a low-current grounding system according to an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the zero-sequence equivalent network for a single-phase grounding fault in a typical multi-outgoing-line low-current grounding system.

[0047] Figure 3 A simplified topology diagram for a typical low-current grounding system;

[0048] Figure 4 for Figure 3 A schematic diagram of the system topology when F2 fails;

[0049] Figure 5 This is a transient zero-sequence power diagram of a neutral-point ungrounded system when a fault occurs at position F1.

[0050] Figure 6 This is a transient zero-sequence power diagram of a neutral-point ungrounded system when a fault occurs at position F2.

[0051] Figure 7 The transient zero-sequence power diagram is shown for a neutral-point ungrounded system when a fault occurs at position F3.

[0052] Figure 8 This is a transient zero-sequence power diagram of a neutral-point grounded system via an arc-suppression coil when a fault occurs at position F1.

[0053] Figure 9 This is a transient zero-sequence power diagram of a neutral-point grounded system via an arc-suppression coil when a fault occurs at position F2.

[0054] Figure 10 This is a transient zero-sequence power diagram for a neutral-point grounded system via an arc-suppression coil when a fault occurs at position F3. Detailed Implementation

[0055] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0056] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0057] Example 1

[0058] In one or more embodiments, a method for locating single-phase grounding fault sections in a low-current grounding system is disclosed, combined with... Figure 1 Specifically, it includes the following steps:

[0059] S101: Based on the abrupt changes in zero-sequence voltage and zero-sequence current at the outlet of the protected section, determine whether to initiate detection for locating a single-phase ground fault section.

[0060] In this embodiment, the difference between the current zero-sequence voltage and zero-sequence current sample values ​​and the corresponding sample values ​​of the previous cycle is calculated. If the absolute value of the zero-sequence voltage difference corresponding to n consecutive sampling points exceeds the preset setting threshold, and / or the absolute value of the zero-sequence current difference corresponding to n consecutive sampling points exceeds the preset setting threshold, then the detection of single-phase ground fault section location is determined to be started, and the fault start point is recorded.

[0061] Specifically, the zero-sequence voltage and zero-sequence current sampling values ​​at both ends of the protected section are obtained through zero-sequence voltage transformers and zero-sequence current transformers, respectively. A protection device (i.e., a measurement point) is installed at the outlet of each section. This device can acquire the zero-sequence voltage and zero-sequence current sampling values ​​at the installation location; and determine whether to activate the single-phase grounding fault location detection based on the abrupt changes in the zero-sequence voltage and zero-sequence current.

[0062] As a specific implementation method, the method for detecting sudden changes in zero-sequence voltage or zero-sequence current is as follows:

[0063] (1) Real-time monitoring of the output sample values ​​of the zero-sequence voltage transformer and the zero-sequence current transformer;

[0064] (2) Calculate the difference between the current zero-sequence voltage and zero-sequence current and the sampled value of the previous cycle. The calculation formula is as follows:

[0065] , ;

[0066] in, , These are the sampled values ​​of the zero-sequence voltage and zero-sequence current for the current cycle, respectively. , These are the sampled values ​​of the zero-sequence voltage and zero-sequence current of the previous adjacent cycle, respectively.

[0067] If the difference between five consecutive zero-sequence voltage or zero-sequence current sampling values ​​exceeds the preset setting threshold, it is determined that the single-phase ground fault section location is activated, and the activation point is recorded. This can improve the accuracy of fault judgment and enhance the method's ability to withstand transition resistance.

[0068] Optionally, the setting threshold value, when selected in practice, takes into account both reliability and the ability to withstand transition resistance, and can be set to 0.1. C~0.2 C Adjust within the range, C This refers to the rated voltage or rated current on the secondary side of the transformer.

[0069] This embodiment employs a composite start-up criterion combining zero-sequence voltage mutation and zero-sequence current mutation. When the zero-sequence voltage change is insignificant or its amplitude is low, this method utilizes the high sensitivity of the zero-sequence current to the transient components of the fault for auxiliary judgment. This effectively overcomes the technical challenge of slow zero-sequence voltage establishment or insufficient amplitude failing to meet the single voltage start-up threshold during high-resistance grounding faults, leading to the fault selection device failing to operate or experiencing delayed response. This significantly improves the system's ability to capture weak fault signals.

[0070] S102: If detection is initiated, the transient zero-sequence power of each section outlet of the low-current grounding system shall be calculated.

[0071] In this embodiment, the exit positioning device of each section first sets the cutoff frequency of the zero-sequence voltage and zero-sequence current after the starting point to be... f Low-pass filtering is applied, and then their respective transient zero-sequence powers are calculated. p 0,i .

[0072] Cutoff frequency f The calculation method is as follows:

[0073] ;

[0074] in, f s This is the frequency at which the line first experiences series resonance. According to the theory of uniform transmission lines, below this frequency, the distributed parameters of the line can be equivalent to capacitive lumped parameters. l i For line length, L 0、 C 0 represents the zero-sequence inductance and zero-sequence capacitance per unit length of the line, respectively.

[0075] Transient zero-sequence power p 0,i The calculation method is as follows:

[0076] ;

[0077] in, , Sections i Zero-sequence voltage and zero-sequence current collected at the measurement point at the outlet and filtered by low-pass filter.

[0078] S103: The integration time window is determined by using zero-crossing detection and continuity verification mechanism, and the transient zero-sequence power is integrated within the corresponding time window to obtain the generalized transient zero-sequence energy.

[0079] In this embodiment, when a single-phase ground fault occurs, the transient zero-sequence power distribution and variation characteristics of the ungrounded neutral system and the system grounded through the arc suppression coil are different.

[0080] exist Figure 2 In the typical low-current grounding system single-phase ground fault capacitive lumped parameter zero-sequence equivalent network shown, for both ungrounded neutral systems and systems grounded via arc suppression coils, the transient zero-sequence power downstream of the fault point can be uniformly expressed as:

[0081] ;

[0082] For a neutral-point ungrounded system, the upstream section of the fault point and the transient zero-sequence power upstream of the fault section can be expressed as:

[0083] ;

[0084] For a neutral point grounded system via an arc suppression coil, the upstream section of the fault point and the transient zero-sequence power upstream of the fault section can be expressed as:

[0085] ;

[0086] in, Let i be the transient zero-sequence power at the output of segment i. , These are the zero-sequence voltage and zero-sequence current collected at the measurement point at the exit of section i, respectively. C i This is the sum of the equivalent capacitance to ground of the downstream segment i from the fault point to the end of the line. C f,i This is the sum of the equivalent ground capacitances upstream of the faulty section and behind section i upstream of the fault point. i L This is for inductor compensation current.

[0087] For both ungrounded neutral systems and systems grounded via arc suppression coils, the transient zero-sequence power downstream of the fault point exhibits non-negative characteristics. For ungrounded neutral systems, the transient zero-sequence power upstream of the fault point and upstream of the fault section exhibits non-positive characteristics. Due to the influence of the inductor compensation current, for systems grounded via arc suppression coils, the sign of the transient zero-sequence power upstream of the fault point and upstream of the fault section is uncertain. However, at the moment of fault occurrence, due to the inertial limitation of the energy established by the arc suppression coil's magnetic field, the inductor compensation current is much smaller than the rapidly rising zero-sequence capacitance current. At this time, the transient zero-sequence power in this segment exhibits non-positive characteristics, similar to the transient characteristics of ungrounded neutral systems, which allows for unified segment location. As the transient process progresses and the compensation current gradually builds up, the transient zero-sequence power undergoes a polarity reversal process from negative to positive.

[0088] In this embodiment, the generalized transient zero-sequence energy is defined as the integral of the transient zero-sequence power over time, specifically expressed as:

[0089] ;

[0090] The polarity of the transient zero-sequence power at a single moment may reverse due to fluctuations in the zero-sequence waveform, thus rendering the single-point criterion invalid. In this embodiment, the transient zero-sequence power is integrated to obtain the generalized transient zero-sequence energy. The positive and negative signs of the generalized transient zero-sequence energy are used for segment positioning, which can avoid the failure of the polarity criterion of the transient zero-sequence power at a single moment caused by fluctuations in the zero-sequence waveform, and greatly improve the accuracy.

[0091] For a neutral-point ungrounded system, i.e., a system grounded through an arc suppression coil, downstream of the fault point, the transient zero-sequence power at the outlet of the corresponding section theoretically exhibits a strictly non-negative or non-positive characteristic, so the integration time window can be arbitrarily selected.

[0092] For the upstream section of the fault point and the upstream section of the fault section in the neutral point grounded by the arc suppression coil, due to the compensation effect of the arc suppression coil, the transient zero-sequence power undergoes a polarity reversal process from negative to positive. To ensure that the generalized transient zero-sequence energy integrated within the time window of this type of section is strictly negative, the time of fault occurrence is taken as the starting point of integration. The zero-crossing point where the transient zero-sequence power changes from negative to positive is located using a zero-crossing detection and continuity verification mechanism as the end point of integration, ensuring that the generalized transient zero-sequence energy integrated in the upstream section of the fault point in the arc suppression coil grounding system is strictly negative; specifically:

[0093] ;

[0094] Wherein, sampling point s is the polarity reversal point of the generalized transient zero-sequence power; Δn is the length of the verification window, which is usually taken as half a cycle of the signal at the low-pass filter cutoff frequency.

[0095] The above formula means:

[0096] If the following conditions are met:

[0097] At the (s-1)th sampling point, the zero-sequence power of the segment is negative; at the next s-th sampling point, the zero-sequence power of the segment becomes non-negative.

[0098] Furthermore, starting from sampling point s, until... For the last Δn consecutive sampling points, the zero-sequence power is greater than zero; where Δ n The length of the verification window;

[0099] This indicates that the sampling point s is determined to be the zero-crossing point of the transient zero-sequence power through the zero-crossing detection and continuity verification mechanism.

[0100] Therefore, for each section of both the neutral-point ungrounded system and the arc-suppression coil grounded system, starting from the abrupt change initiation point, if the zero-crossing moment of the transient zero-sequence energy can be determined through zero-crossing detection and continuity verification mechanisms, then the integration time window is from the initiation point to the zero-crossing moment. Integrating within this time window ensures that the generalized transient zero-sequence energy of the faulted section of the arc-suppression coil grounded system is strictly negative, maximizing the positive-negative difference between it and the non-faulted section. If not, the integration time window is determined to be a fixed time window (e.g., 10ms) starting from the initiation moment, and the generalized transient zero-sequence energy at the exit of each section is obtained by integrating within the corresponding time window.

[0101] This embodiment uses only low-pass filtering to process the sampled data. While ensuring the simplification of the line structure, it can also reduce high-frequency interference during the calculation of transient zero-sequence power derivative. By using zero-crossing detection and continuity verification, the optimal integration window can be adaptively determined, cleverly avoiding the interference of transient zero-sequence power polarity reversal phenomenon. It unifies the section location criteria of neutral point ungrounded system and resonant grounded system, maximizes the polarity difference of generalized transient zero-sequence energy between fault section and non-fault section, and is not affected by transition resistance and line changes, thus having high reliability.

[0102] S104: Based on the sign of the generalized transient zero-sequence energy at the exit of the protected section, determine whether the fault point is upstream or downstream of the current measurement point. If the fault point is upstream of the current measurement point, compare the sign of the generalized transient zero-sequence energy values ​​corresponding to the current measurement point and the upstream adjacent section measurement point to determine whether the section between the two measurement points is the fault section.

[0103] When a single-phase grounding fault occurs in a low-current grounding system, the generalized transient zero-sequence energy of the downstream section of the fault point is positive; the generalized transient zero-sequence energy of the upstream section of the fault point and the upstream section of the fault section is negative.

[0104] As a specific example, combined with Figure 4 The following is a simplified topology diagram of a low-current grounding system when F2 fails; Section I is the upstream section of the fault point, Section II is the fault section, and Section III is the downstream section of the fault point; the generalized transient zero-sequence energy at K11 and K12 is negative, and the generalized transient zero-sequence energy at K13 is positive.

[0105] Therefore, if the generalized transient zero-sequence energy at the exit of the protected section is positive, the fault point is determined to be upstream of the current section exit measurement point; if the generalized transient zero-sequence energy at the exit of the protected section is negative, the fault point is determined to be downstream of the current section exit measurement point.

[0106] When the fault point is located upstream of the current segment's exit measurement point, the generalized transient zero-sequence energy value (positive value) of the currently protected segment is sent to the upstream adjacent segment measurement point; the positive and negative differences in the generalized transient zero-sequence energy at the current segment's exit measurement point and the upstream segment's exit measurement point are compared to determine whether the segment between the two measurement points is a fault segment. The specific judgment logic is as follows:

[0107] If the product of the generalized transient zero-sequence energy of the outlet measuring points of adjacent sections is negative, that is, the positive and negative polarities are opposite, then the section between the two measuring points can be determined as the fault section, and an alarm or trip signal will be given according to the location result, and the fault location is completed.

[0108] If the product of the generalized transient zero-sequence energy at the outlet measuring points of adjacent sections is positive, that is, the generalized transient zero-sequence energy value at the outlet measuring point of the upstream section is also positive, then the section between the two measuring points is determined to be a non-fault section (downstream of the fault point), and the location procedure is reset.

[0109] When the fault point is located downstream of the current segment exit measurement point, there is no need to compare the difference in generalized transient zero-sequence energy between the current measurement point and the upstream adjacent measurement point (because they are both negative values). The current segment exit measurement point also does not need to send its energy value upstream and does not participate in segment positioning, thereby reducing communication.

[0110] Furthermore, if the protected section is the last section of the line and cannot receive generalized transient zero-sequence energy from downstream sections, then the sign of the generalized transient zero-sequence energy at the exit measuring point of this section can be used to directly determine whether the last section is a faulty section. The specific judgment logic is as follows:

[0111] If the generalized transient zero-sequence energy at the outlet measuring point of this section is negative, the last section can be determined to be a faulty section, and an alarm or trip signal will be given according to the positioning result, and the fault positioning is completed; otherwise, it is determined to be a healthy section, and the positioning procedure will reset.

[0112] This embodiment utilizes the transient zero-sequence current characteristics in the early stage of a ground fault to unify the location criteria for neutral-point ungrounded systems and resonant grounded systems. It also maximizes the positive and negative differences of the generalized transient zero-sequence energy value through an adaptive integration strategy, effectively improving the reliability and sensitivity of single-phase ground fault location.

[0113] In this embodiment, a typical low-current grounding system model is built using PSCAD / EMTDC simulation software, and the proposed method for locating single-phase grounding fault sections in a low-current grounding system based on generalized transient zero-sequence energy is simulated and verified.

[0114] (1) Model establishment:

[0115] Typical low-current grounding system model as follows Figure 3As shown, the simulation includes three outgoing lines (L1, L2, L3). Line L1 is designated as the faulty line under test, with a total length of 10km. It is divided into three sections to allow for setting fault points at different locations. K11, K12, and K13 are the measurement points at the exit of each section, respectively. Lines L2 and L3 are non-faulty lines, each 10km in length. All lines use a cable model with the following zero-sequence parameters: R0 = 1.81Ω / km, L0 = 1.207mH / km, C0 = 0.267μF / km, and the arc suppression coil has an overcompensation of 8% and an inductance of 0.532H. The initial series resonant frequency of the lines is 2116Hz. In the simulation, all acquired zero-sequence voltage and current signals were low-pass filtered with a cutoff frequency of 211.6Hz.

[0116] (2) Simulation analysis:

[0117] To verify the feasibility of the single-phase grounding fault section location method for a small-current grounding system based on generalized transient zero-sequence energy proposed in this embodiment, single-phase grounding fault experiments were conducted at three fault points: F1, F2, and F3. The calculation results of the generalized transient zero-sequence energy at the outlet of each section are recorded in Tables 1, 2, and 3. Table 1 compares the generalized transient zero-sequence energy of each section when a single-phase grounding fault occurs at different fault locations with a transition resistance of 1000Ω. Table 2 compares the generalized transient zero-sequence energy of each section when a single-phase grounding fault occurs in section 1 with different transition resistances. Table 3 compares the generalized transient zero-sequence energy of each section under different initial phase angles when a single-phase grounding fault occurs in section 2 with a transition resistance of 1000Ω.

[0118] Meanwhile, the transient zero-sequence power of a neutral-point ungrounded system and a system grounded via an arc suppression coil when a single-phase ground fault with a transition resistance of 1000Ω occurs at different fault locations is displayed respectively. Figure 5-7 and Figure 8-10 middle.

[0119] Table 1. Impact of different fault locations on the method

[0120]

[0121] Table 2. Effect of different transition resistances on the method

[0122]

[0123] Table 3. Influence of different initial phase angles of faults on the method

[0124]

[0125] Depend on Figure 5-6It is known that when a single-phase ground fault with a transition resistance of 1000Ω occurs at different locations in a neutral ungrounded system, no polarity reversal occurs in the upstream section of the fault point and the upstream section of the fault. The zero-crossing detection and continuity verification mechanism proposed in this embodiment cannot determine the transient zero-sequence power polarity reversal point, and a fixed time window (10ms) from the start time is used for integration.

[0126] Depend on Figure 8-10 It can be seen that when a single-phase ground fault with a transition resistance of 1000Ω occurs at different locations in a neutral point grounded system via an arc suppression coil, the zero-crossing detection and continuity verification mechanism proposed in this embodiment can correctly lock the upstream section of the fault point and the transient zero-sequence power polarity reversal point upstream of the fault section, and adaptively determine the time window for integration.

[0127] As can be seen from the data in Tables 1 to 3, the method proposed in this embodiment can correctly determine the fault location under different fault locations, transition resistances, and initial phase angles of the fault.

[0128] Example 2

[0129] In one or more embodiments, a single-phase grounding fault location system for a low-current grounding system is disclosed, comprising:

[0130] The fault detection module is used to determine whether to initiate the detection of single-phase grounding fault section location based on the abrupt changes in zero-sequence voltage and zero-sequence current at the outlet of the protected section.

[0131] The transient zero-sequence power calculation module is used to calculate the transient zero-sequence power of each section outlet of the low-current grounding system after the start detection.

[0132] The transient zero-sequence energy calculation module is used to determine the integration time window using zero-crossing detection and continuity verification mechanisms, and to integrate the transient zero-sequence power within the corresponding time window to obtain the generalized transient zero-sequence energy.

[0133] The fault location module is used to determine whether the fault point is upstream or downstream of the current measurement point based on the sign of the generalized transient zero-sequence energy at the exit of the protected section. If the fault point is upstream of the current measurement point, the module compares the sign of the generalized transient zero-sequence energy values ​​corresponding to the current measurement point and the measurement points of the adjacent upstream section to determine whether the section between the two measurement points is the fault section.

[0134] It should be noted that the specific implementation methods of the above modules are exactly the same as those in Example 1, and will not be described in detail again.

[0135] Example 3

[0136] In one or more embodiments, a terminal device is disclosed, comprising a processor and a memory, wherein the processor is used to implement instructions; and the memory is used to store multiple instructions adapted to be loaded by the processor and executed as described in Embodiment 1 for locating single-phase grounding fault sections in a low-current grounding system.

[0137] It should be understood that in this embodiment, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc.

[0138] Memory may include read-only memory and random access memory, and provides instructions and data to the processor. A portion of memory may also include non-volatile random access memory. For example, memory may also store information about the device type.

[0139] In the implementation process, each step of the above method can be completed by the integrated logic circuits in the processor hardware or by software instructions.

[0140] Example 4

[0141] In one or more embodiments, a computer-readable storage medium is disclosed, wherein a plurality of instructions are stored, the instructions being adapted to be loaded by a processor of a terminal device and executed by the single-phase grounding fault location method for a low-current grounding system described in Embodiment 1.

[0142] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for locating a single-phase grounding fault section in a low-current grounding system, characterized in that, include: Based on the abrupt changes in zero-sequence voltage and zero-sequence current at the outlet of the protected section, determine whether to initiate detection for locating a single-phase grounding fault section. If detection is initiated, the transient zero-sequence power of each section outlet of the low-current grounding system is calculated separately. An integration time window is determined using a zero-crossing detection and continuity verification mechanism. Within this time window, the transient zero-sequence power is integrated to obtain the generalized transient zero-sequence energy. Specifically, determining the integration time window using the zero-crossing detection and continuity verification mechanism involves: Based on the zero-crossing detection and continuity verification mechanism of transient zero-sequence power, if the zero-crossing time point is determined, the integration time window is from the fault start point to the zero-crossing time point; if the zero-crossing time point cannot be determined, the integration time window is a fixed time window starting from the fault start point. The zero-crossing detection and continuity verification mechanism based on transient zero-sequence power is as follows: Determine if the following conditions are met: At the (s-1)th sampling point, the zero-sequence power of the segment is negative; at the next s-th sampling point, the zero-sequence power of the segment becomes non-negative. Furthermore, starting from sampling point s, until... End of continuous Δ n All sampling points satisfy the condition that the zero-sequence power is greater than zero; among them, Δ n The length of the verification window; If satisfied, then sampling point s is the zero-crossing point of the transient zero-sequence power; Based on the sign of the generalized transient zero-sequence energy at the exit of the protected section, determine whether the fault point is upstream or downstream of the current measurement point. If the fault point is upstream of the current measurement point, compare the sign of the generalized transient zero-sequence energy values ​​corresponding to the current measurement point and the measurement points of the adjacent upstream section to determine whether the section between the two measurement points is the fault section.

2. The method for locating a single-phase grounding fault section in a low-current grounding system as described in claim 1, characterized in that, Based on the abrupt changes in zero-sequence voltage and zero-sequence current at the outlet of the protected section, it is determined whether to initiate single-phase grounding fault location detection, specifically as follows: Calculate the difference between the current zero-sequence voltage and zero-sequence current sample values ​​and the corresponding sample values ​​of the previous cycle; If the absolute value of the zero-sequence voltage difference corresponding to n consecutive sampling points exceeds the preset setting threshold, and / or the absolute value of the zero-sequence current difference corresponding to n consecutive sampling points exceeds the preset setting threshold, then the detection of single-phase grounding fault section location is initiated, and the fault initiation point is recorded.

3. The method for locating a single-phase grounding fault section in a low-current grounding system as described in claim 1, characterized in that, The sign of the generalized transient zero-sequence energy at the exit of the protected section determines whether the fault point is upstream or downstream of the current measurement point. Specifically: If the generalized transient zero-sequence energy at the exit of the protected section is positive, the fault point is determined to be upstream of the current section exit measurement point; if the generalized transient zero-sequence energy at the exit of the protected section is negative, the fault point is determined to be downstream of the current section exit measurement point.

4. A method for locating a single-phase grounding fault section in a low-current grounding system as described in claim 1 or 3, characterized in that, If the fault point is located upstream of the current measurement point, compare the positive and negative relationships of the generalized transient zero-sequence energy values ​​corresponding to the current measurement point and the measurement points in the adjacent upstream section to determine whether the section between the two measurement points is a fault section. Specifically: If the positive and negative polarities of the generalized transient zero-sequence energy at the outlet measurement points of two adjacent sections are opposite, then the section between the two measurement points is determined to be a fault section. If the generalized transient zero-sequence energy at the exit measurement points of two adjacent sections is positive, then the section between the two measurement points is determined to be a non-fault section.

5. The method for locating a single-phase grounding fault section in a low-current grounding system as described in claim 1, characterized in that, If the protected section is the last section, then the sign of the generalized transient zero-sequence energy at the measurement point at the exit of the protected section is used to determine whether the last section is a fault section; the specific judgment logic is as follows: If the generalized transient zero-sequence energy at the exit measurement point of the protected section is negative, then the protected section is determined to be a fault section. If the generalized transient zero-sequence energy at the exit measurement point of the protected section is positive, then the protected section is determined to be a non-fault section.

6. A single-phase grounding fault location system for a low-current grounding system, characterized in that, include: The fault detection module is used to determine whether to initiate the detection of single-phase grounding fault section location based on the abrupt changes in zero-sequence voltage and zero-sequence current at the outlet of the protected section. The transient zero-sequence power calculation module is used to calculate the transient zero-sequence power of each section outlet of the low-current grounding system after the start detection. The transient zero-sequence energy calculation module is used to determine the integration time window using a zero-crossing detection and continuity verification mechanism, and to integrate the transient zero-sequence power within the corresponding time window to obtain the generalized transient zero-sequence energy; the determination of the integration time window using the zero-crossing detection and continuity verification mechanism specifically involves: Based on the zero-crossing detection and continuity verification mechanism of transient zero-sequence power, if the zero-crossing time point is determined, the integration time window is from the fault start point to the zero-crossing time point; if the zero-crossing time point cannot be determined, the integration time window is a fixed time window starting from the fault start point. The zero-crossing detection and continuity verification mechanism based on transient zero-sequence power is as follows: Determine if the following conditions are met: At the (s-1)th sampling point, the zero-sequence power of the segment is negative; at the next s-th sampling point, the zero-sequence power of the segment becomes non-negative. Furthermore, starting from sampling point s, until... End of continuous Δ n All sampling points satisfy the condition that the zero-sequence power is greater than zero; among them, Δ n The length of the verification window; If satisfied, then sampling point s is the zero-crossing point of the transient zero-sequence power; The fault location module is used to determine whether the fault point is upstream or downstream of the current measurement point based on the sign of the generalized transient zero-sequence energy at the exit of the protected section. If the fault point is upstream of the current measurement point, the module compares the sign of the generalized transient zero-sequence energy values ​​corresponding to the current measurement point and the measurement points of the adjacent upstream section to determine whether the section between the two measurement points is the fault section.

7. A terminal device comprising a processor and a memory, the processor for implementing instructions; the memory for storing multiple instructions, characterized in that, The instructions are adapted to be loaded by a processor and executed as described in any one of claims 1-5, the method for locating single-phase grounding fault sections in a low-current grounding system.

8. A computer-readable storage medium storing a plurality of instructions, characterized in that, The instructions are adapted to be loaded by the processor of the terminal device and executed as described in any one of claims 1-5, the method for locating single-phase grounding fault sections in a low-current grounding system.

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