CN-122017455-A - High-resistance ground fault detection method and system based on zero sequence voltage period differential energy

CN122017455ACN 122017455 ACN122017455 ACN 122017455ACN-122017455-A

Abstract

The application relates to the technical field of power distribution network protection, and provides a high-resistance ground fault detection method based on zero sequence voltage period differential energy, which comprises the steps of collecting instantaneous values of three-phase voltages in real time, and calculating to obtain a continuous zero sequence voltage discrete time sequence according to the instantaneous values of the three-phase voltages; the method comprises the steps of carrying out periodic interception and alignment treatment on the zero sequence voltage discrete time sequence, calculating point-to-point difference values of adjacent periodic zero sequence voltage waveforms after alignment to generate a periodic differential sequence, carrying out squaring and accumulation operation on all the difference values in the periodic differential sequence, carrying out smooth filtering treatment to obtain a periodic differential energy value representing fault characteristics, continuously comparing the periodic differential energy value with a self-adaptively set dynamic threshold value, and generating a high-resistance ground fault judging signal and a corresponding control instruction when the periodic differential energy value continuously exceeds the dynamic threshold value for a preset duration. The method improves the reliability of high-resistance ground fault detection.

Inventors

ZHAO YONG
XING MINGTAO
YU ZHONGHUA
TANG QI
LIU ZHEN
YANG GANG
WANG HAN
CUI JIASHUO
LIANG QINGYUN
MA YUEHUA
ZENG XINSHUN

Assignees

国网河南省电力公司郑州供电公司

Dates

Publication Date: 20260512
Application Date: 20260210

Claims (8)

1. The high-resistance ground fault detection method based on zero sequence voltage period differential energy is characterized by comprising the following steps of: Collecting instantaneous values of the three-phase voltage in real time, and calculating to obtain a continuous zero sequence voltage discrete time sequence according to the instantaneous values of the three-phase voltage; Performing period interception and alignment treatment on the zero sequence voltage discrete time sequence, calculating point-by-point differences of aligned adjacent period zero sequence voltage waveforms, and generating a period differential sequence; performing square and accumulation operation on all differences in the periodic differential sequence, and performing smoothing filtering treatment to obtain periodic differential energy values representing fault characteristics; And continuously comparing the periodic differential energy value with a self-adaptive set dynamic threshold value, and generating a high-resistance ground fault judging signal and a corresponding control instruction when the periodic differential energy value continuously exceeds the dynamic threshold value for a preset duration.
2. The method for detecting the high-resistance ground fault based on the zero-sequence voltage cycle differential energy according to claim 1, wherein the real-time acquisition of the instantaneous value of the three-phase voltage and the calculation of the continuous zero-sequence voltage discrete time sequence according to the instantaneous value of the three-phase voltage comprise the following steps: Synchronously acquiring instantaneous signals of the three-phase voltage at a sampling frequency which is not lower than twice the number of corresponding sampling points of a fundamental frequency period of the system; Algebraic summation is carried out on the instantaneous values of the three-phase voltages at each sampling moment, and average operation is carried out to obtain instantaneous sampling values of the zero sequence voltages; And storing the calculated continuous zero sequence voltage instantaneous sampling values in a first-in first-out data buffer area in time sequence to form the zero sequence voltage discrete time sequence.
3. The method for detecting a high-impedance ground fault based on zero-sequence voltage periodic differential energy according to claim 1, wherein the performing the periodic interception and alignment processing on the zero-sequence voltage discrete time sequence, calculating the point-by-point difference value of the aligned adjacent periodic zero-sequence voltage waveforms, and generating a periodic differential sequence comprises: Intercepting the data of the latest complete power frequency period from the data buffer zone of the zero sequence voltage discrete time sequence as a current period sequence and intercepting the data of the immediately previous complete power frequency period as a reference period sequence; Performing cross-correlation operation on the current periodic sequence and the reference periodic sequence to determine a phase offset with highest waveform similarity, and performing cyclic shift alignment on the current periodic sequence according to the phase offset; and calculating the numerical value difference value of the aligned current periodic sequence and the reference periodic sequence at each corresponding sampling point, so as to generate the periodic differential sequence.
4. A method for detecting a high-impedance ground fault based on zero-sequence voltage cycle differential energy according to claim 3, wherein said cross-correlating the current cycle sequence with the reference cycle sequence to determine the phase offset that maximizes the similarity of the waveforms of the two, comprises: Calculating cross-correlation function values under different phase offsets based on the current periodic sequence and the reference periodic sequence; Determining a phase offset for maximizing the cross-correlation function value, and taking the phase offset as an optimal phase calibration parameter; and performing cyclic shift on the current periodic sequence based on the optimal phase calibration parameters, thereby completing accurate alignment of the zero sequence voltage waveforms of adjacent power frequency periods.
5. The method for detecting the high-resistance ground fault based on the zero-sequence voltage periodic differential energy according to claim 1, wherein the squaring and accumulating operation is performed on all differences in the periodic differential sequence, and the periodic differential energy value representing the fault characteristic is obtained through smoothing filtering processing, and the method comprises the following steps: performing a squaring operation on each difference element in the periodic differential sequence; Summing all the results after square operation, and multiplying the summed results by a sampling time interval to obtain an original differential energy value in a power frequency period; and processing the plurality of original differential energy values obtained by continuous calculation by adopting a moving average filtering method, and outputting the smoothed periodic differential energy values.
6. The method for detecting a high-resistance ground fault based on zero-sequence voltage periodic differential energy according to claim 1, wherein the continuously comparing the periodic differential energy value with an adaptively set dynamic threshold value, and generating a high-resistance ground fault determination signal and a corresponding control command when the periodic differential energy value continuously exceeds the dynamic threshold value for a preset period of time, comprises: Continuously recording the periodic differential energy values in a plurality of power frequency periods in a fault-free operation stage of the system, and calculating a statistical average value and a standard deviation of the periodic differential energy values; setting an initial dynamic threshold based on the statistical average and standard deviation; In a real-time detection stage, comparing each latest calculated periodic differential energy value with the current effective dynamic threshold value; and if the duration time of the periodic differential energy value continuously exceeding the dynamic threshold reaches or exceeds a preset power frequency period number, judging that a high-resistance ground fault occurs, and generating the high-resistance ground fault judging signal containing a fault alarm or protection tripping instruction.
7. The method for detecting the high-resistance ground fault based on the zero-sequence voltage cycle differential energy according to claim 6, wherein the setting of the initial dynamic threshold based on the statistical average and standard deviation comprises calculating an arithmetic average of the periodic differential energy values in a plurality of power frequency periods recorded in a system fault-free operation stage as a background energy reference; Calculating standard deviation of the periodic differential energy values in the power frequency periods to represent the fluctuation range of background energy; And calculating and setting the initial dynamic threshold according to a preset reliable coefficient based on the background energy reference and the standard deviation.
8. A high resistance ground fault detection system based on zero sequence voltage period differential energy, comprising: The acquisition module is used for acquiring the instantaneous value of the three-phase voltage in real time and calculating to obtain a continuous zero sequence voltage discrete time sequence according to the instantaneous value of the three-phase voltage; the first calculation module is used for carrying out period interception and alignment treatment on the zero sequence voltage discrete time sequence, calculating the point-by-point difference value of the aligned adjacent period zero sequence voltage waveform and generating a period difference sequence; The second calculation module is used for carrying out square and accumulation operation on all the differences in the periodic differential sequence, and obtaining periodic differential energy values representing fault characteristics through smoothing filter processing; And the comparison module is used for continuously comparing the periodic differential energy value with a self-adaptively set dynamic threshold value, and generating a high-resistance ground fault judgment signal and a corresponding control instruction when the periodic differential energy value continuously exceeds the dynamic threshold value for a preset duration.

Description

High-resistance ground fault detection method and system based on zero sequence voltage period differential energy Technical Field The application relates to the technical field of power distribution network protection, in particular to a high-resistance ground fault detection method and system based on zero sequence voltage period differential energy. Background In the operation of a power distribution network with an ineffective grounding neutral point, single-phase grounding faults are the fault type with the highest occurrence rate, the reliable detection of the single-phase grounding faults is important to guaranteeing the power supply safety and continuity, and the identification of high-resistance grounding faults with weak fault currents and unobvious characteristics is a technical difficulty of long-term attention. The existing detection method mainly depends on steady state quantity analysis of amplitude, phase or harmonic components of zero-sequence voltage or zero-sequence current, however, the change of an electrical signal generated by a high-resistance grounding fault is extremely weak and is easily submerged by normal load fluctuation, three-phase imbalance and measurement noise of a system, so that the technical problems of insufficient sensitivity and difficult setting of the traditional protection device are caused, and reliable identification of the high-resistance grounding fault of the low-current grounding system is difficult to realize. Disclosure of Invention In view of the above, the present invention provides a method and a system for detecting a high-resistance ground fault based on zero-sequence voltage period differential energy, so as to solve the problems set forth in the above background art. In a first aspect, the application provides a high-resistance ground fault detection method based on zero sequence voltage period differential energy, which comprises the following steps: Collecting instantaneous values of the three-phase voltage in real time, and calculating to obtain a continuous zero sequence voltage discrete time sequence according to the instantaneous values of the three-phase voltage; Performing period interception and alignment treatment on the zero sequence voltage discrete time sequence, calculating point-by-point differences of aligned adjacent period zero sequence voltage waveforms, and generating a period differential sequence; performing square and accumulation operation on all differences in the periodic differential sequence, and performing smoothing filtering treatment to obtain periodic differential energy values representing fault characteristics; And continuously comparing the periodic differential energy value with a self-adaptive set dynamic threshold value, and generating a high-resistance ground fault judging signal and a corresponding control instruction when the periodic differential energy value continuously exceeds the dynamic threshold value for a preset duration. In a second aspect, the present application provides a high-resistance ground fault detection system based on zero sequence voltage period differential energy, including: The acquisition module is used for acquiring the instantaneous value of the three-phase voltage in real time and calculating to obtain a continuous zero sequence voltage discrete time sequence according to the instantaneous value of the three-phase voltage; the first calculation module is used for carrying out period interception and alignment treatment on the zero sequence voltage discrete time sequence, calculating the point-by-point difference value of the aligned adjacent period zero sequence voltage waveform and generating a period difference sequence; The second calculation module is used for carrying out square and accumulation operation on all the differences in the periodic differential sequence, and obtaining periodic differential energy values representing fault characteristics through smoothing filter processing; And the comparison module is used for continuously comparing the periodic differential energy value with a self-adaptively set dynamic threshold value, and generating a high-resistance ground fault judgment signal and a corresponding control instruction when the periodic differential energy value continuously exceeds the dynamic threshold value for a preset duration. The application provides a high-resistance ground fault detection method and a system based on zero sequence voltage period differential energy. The method comprises the steps of calculating point-by-point difference values of adjacent periodic zero sequence voltage waveforms and converting the point-by-point difference values into energy values, amplifying tiny distortion characteristics which are caused by high-resistance ground faults and are shown as inconsistent in adjacent periodic waveforms, enabling weak fault characteristics to be displayed, enabling a judgment standard to be attached to an actual background noise level of