CN-121978468-A - Method and system for positioning single-phase grounding fault section of low-current grounding system

CN121978468ACN 121978468 ACN121978468 ACN 121978468ACN-121978468-A

Abstract

The invention belongs to the technical field of single-phase earth fault positioning of a power distribution network, and particularly discloses a single-phase earth fault section positioning method and system of a small-current grounding system; the method comprises the steps of determining whether to start detection of single-phase grounding fault zone positioning based on the sudden change of zero sequence voltage and zero sequence current at the outlet of a protected zone, calculating respective transient zero sequence power at each zone outlet of a small-current grounding system if the detection is started, determining an integration time window by utilizing a zero-crossing detection and continuity check mechanism, integrating the transient zero sequence power in the corresponding time window to obtain generalized transient zero sequence energy, judging whether a fault point is located upstream or downstream of a current measurement point based on the positive and negative of the generalized transient zero sequence energy at the outlet of the protected zone, and further judging whether the zone between the two measurement points is a fault zone. The invention 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 transition resistance and line variation.

Inventors

GAO HOULEI
WANG YAN

Assignees

山东大学

Dates

Publication Date: 20260505
Application Date: 20260407

Claims (10)

1. A method for locating a single-phase earth fault section of a low-current earth system, comprising: Determining whether to initiate detection of single-phase earth fault zone location based on the sudden change in zero sequence voltage and zero sequence current at the exit of the protected zone; If the detection is started, the outlets of all sections of the low-current grounding system respectively calculate the respective transient zero sequence power; determining an integration time window by utilizing a zero-crossing detection and continuity check mechanism, and integrating the transient zero-sequence power in the corresponding time window to obtain generalized transient zero-sequence energy; And judging whether the fault point is positioned at the upstream or downstream of the current measurement point based on the positive and negative of the generalized transient zero sequence energy at the outlet of the protected section, and if the fault point is positioned at the upstream of the current measurement point, comparing the positive and negative relations of generalized transient zero sequence energy values corresponding to the current measurement point and the upstream adjacent section measurement point, and judging whether the section between the two measurement points is the fault section.
2. The method for locating a single-phase earth fault section of a low-current earth system according to claim 1, wherein the determining whether to start the detection of the single-phase earth fault section location is based on the zero sequence voltage and the abrupt change of the zero sequence current at the exit of the protected section is specifically: calculating the difference value between the current zero sequence voltage and the sampling value of the zero sequence current and the sampling value corresponding to the previous cycle wave; If the absolute values of the zero sequence voltage differences corresponding to the n continuous sampling points exceed the preset setting threshold, and/or the absolute values of the zero sequence current differences corresponding to the n continuous sampling points exceed the preset setting threshold, the detection of single-phase grounding fault section positioning is judged to be started, and the fault starting point is recorded.
3. The method for locating a single-phase earth fault section of a low-current earth system according to claim 1, wherein the integration time window is determined by using a zero-crossing detection and continuity check mechanism, specifically: Based on a zero-crossing detection and continuity verification mechanism of transient zero-sequence power, if a zero-crossing moment is determined, the integration time window is a fault starting point to the zero-crossing moment, and if the zero-crossing moment cannot be determined, the integration time window is a fixed time window from the fault starting point.
4. A method for locating a single-phase earth fault section of a low-current grounding system according to claim 3, wherein the zero-crossing detection and continuity check mechanism based on transient zero-sequence power is specifically as follows: Judging whether the following conditions are satisfied: at the s-1 th sampling point, the zero sequence power of the section is negative, and at the next s sampling point, the zero sequence power of the section becomes non-negative; And, starting from the sampling point s, to The finished continuous delta n sampling points all meet the condition that the zero sequence power is greater than zero, wherein delta n is the length of a check window; and if so, the sampling point s is the zero crossing point of the transient zero-sequence power.
5. The method for locating a single-phase grounding fault section of a small-current grounding system according to claim 1, wherein the fault point is located upstream or downstream of a current measurement point based on positive and negative of generalized transient zero sequence energy at an outlet of the protected section, specifically comprises the following steps: If the generalized transient zero sequence energy at the exit of the protected section is a positive value, the fault point is judged to be positioned at the upstream of the current section exit measuring point, and if the generalized transient zero sequence energy at the exit of the protected section is a negative value, the fault point is judged to be positioned at the downstream of the current section exit measuring point.
6. The method for locating a single-phase grounding fault section of a low-current grounding system according to claim 1 or 5, wherein if the fault point is located upstream of a current measurement point, comparing positive and negative relations of generalized transient zero sequence energy values corresponding to the current measurement point and upstream adjacent section measurement points, and judging whether a section between two measurement points is a fault section, specifically: if the positive and negative polarities of the generalized transient zero sequence energy at the outlet measuring points of the two adjacent sections are opposite, judging that the section between the two measuring points is a fault section; If the generalized transient zero sequence energy at the outlet measuring points of two adjacent sections is positive, judging that the section between the two measuring points is a non-fault section.
7. The method for locating a single-phase grounding fault section of a low-current grounding system according to claim 1, wherein if the protected section is an endmost section, determining whether the last section is a fault section according to the positive and negative of generalized transient zero sequence energy at an exit measurement point of the protected section, wherein the specific determination logic is as follows: if the generalized transient zero sequence energy of the exit measuring point of the protected section is a negative value, judging that the protected section is a fault section; and if the generalized transient zero sequence energy of the exit measurement point of the protected section is a positive value, judging that the protected section is a non-fault section.
8. A low current grounding system single phase earth fault section localization system comprising: The fault detection module is used for determining whether to start the detection of the single-phase grounding fault section positioning or not based on the sudden change of the zero sequence voltage and the zero sequence current at the outlet of the protected section; The transient zero sequence power calculation module is used for calculating the respective transient zero sequence power of each section outlet of the low-current grounding system after starting detection; The transient zero-sequence energy calculation module is used for determining an integration time window by utilizing a zero-crossing detection and continuity check mechanism, and integrating the transient zero-sequence power in the corresponding time window to obtain generalized transient zero-sequence energy; The fault positioning module is used for judging whether the fault point is located on the upstream or downstream of the current measurement point based on the positive and negative of the generalized transient zero sequence energy at the outlet of the protected section, and if the fault point is located on the upstream of the current measurement point, comparing the positive and negative relations of the generalized transient zero sequence energy values corresponding to the current measurement point and the upstream adjacent section measurement point, and judging whether the section between the two measurement points is the fault section.
9. A terminal device comprising a processor for implementing instructions and a memory for storing a plurality of instructions, characterized in that the instructions are adapted to be loaded by the processor and to perform the method for locating a single phase earth fault section of a low current grounding system according to any one of claims 1-7.
10. A computer readable storage medium having stored therein a plurality of instructions adapted to be loaded by a processor of a terminal device and to perform the low current grounding system single phase earth fault section localization method of any one of claims 1-7.

Description

Method and system for positioning single-phase grounding fault section of low-current grounding system Technical Field The invention relates to the technical field of single-phase earth fault positioning of distribution networks, in particular to a method and a system for positioning a single-phase earth fault section of a low-current grounding system. Background The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art. The low-current grounding mode is widely adopted in the medium-low voltage distribution network, and the system can operate for a period of time with faults in the grounding mode, but the faults exist for a long time, so that serious accidents such as interphase short circuit and the like can be caused, and the safe and stable operation of the power system is seriously threatened. Therefore, it is important to quickly and accurately locate the single-phase earth fault of the low-current earth system. Aiming at the positioning of single-phase earth faults of a low-current grounding system, the prior art mostly adopts a line selection positioning method based on transient current or zero sequence current, but the method is easily influenced by the compensation characteristic of an arc suppression coil and line change. The prior art also discloses methods for fault location by using transient energy or power integration, which mostly adopt empirical fixed time windows for integral calculation, however, transient zero sequence power is dynamically influenced by a fault initial phase angle, system parameters and a compensation degree of an arc suppression coil, the fixed time windows are in a theoretical lack of rigor, cannot adapt to different fault scenes, and are extremely easy to cause location failure due to the fact that the integration crosses the boundary. Although some methods introduce complex algorithms such as wavelet packet transformation and the like to screen frequency bands, the method has large calculation amount and high complexity and is not easy to realize in a protection device of an engineering site. Disclosure of Invention In order to solve the problems, the invention provides a single-phase grounding fault section positioning method and a single-phase grounding fault section positioning system for a small-current grounding system, which integrate transient zero sequence power by utilizing a zero-crossing detection and continuity checking mechanism to adaptively determine an optimal time window, maximize positive and negative differences of generalized transient zero sequence energy of a fault section and a non-fault section, position the fault section by utilizing positive and negative polarities of local and adjacent transient zero sequence energy, and use a plurality of electric quantities at different positions in a calculation process, thereby improving the reliability and the sensitivity of the positioning method. In some embodiments, the following technical scheme is adopted: a small current grounding system single-phase grounding fault section positioning method comprises the following steps: Determining whether to initiate detection of single-phase earth fault zone location based on the sudden change in zero sequence voltage and zero sequence current at the exit of the protected zone; If the detection is started, the outlets of all sections of the low-current grounding system respectively calculate the respective transient zero sequence power; determining an integration time window by utilizing a zero-crossing detection and continuity check mechanism, and integrating the transient zero-sequence power in the corresponding time window to obtain generalized transient zero-sequence energy; And judging whether the fault point is positioned at the upstream or downstream of the current measurement point based on the positive and negative of the generalized transient zero sequence energy at the outlet of the protected section, and if the fault point is positioned at the upstream of the current measurement point, comparing the positive and negative relations of generalized transient zero sequence energy values corresponding to the current measurement point and the upstream adjacent section measurement point, and judging whether the section between the two measurement points is the fault section. As a further scheme, based on the sudden change of the zero sequence voltage and the zero sequence current at the outlet of the protected section, whether to start the detection of the single-phase grounding fault section positioning is determined, specifically: calculating the difference value between the current zero sequence voltage and the sampling value of the zero sequence current and the sampling value corresponding to the previous cycle wave; If the absolute values of the zero sequence voltage differences corresponding to the n continuous sampling points exceed the preset setting thres