Small current grounding system single-phase ground fault line selection method based on fisher information

Abstract

The invention discloses a small current grounding system single-phase ground fault line selection method based on fisher information. The method includes: S1, a discrete wavelet coefficient is divided into a series of time windows; S2, data points in each time window are packaged into a state; S3, a probability density function pi based on possibility of observing a system state is established in each time window; S4, the fisher information is calculated from the probability density function for each time window; and S5, a line with the minimum fisher information value is selected to be a fault line. By means of the method, under different grounding methods, fault lines and non-fault lines can be distinguished effectively, effects of voltage initial phase angles, ground resistance and fault location are avoided, and fault moments can be located accurately. Under the adverse conditions of short data, small amplitudes and disturbance existence and the like, feature information hidden in a signal sequence can be effectively extracted, simultaneously a complex degree of each signal sequence can be expressed quantitatively, and an effective means for analyzing a non-stable signal sequence is provided.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a method for line selection for single-phase grounding faults in small current grounding systems based on Fisher information. Background technique [0002] Most of the neutral points of my country's medium and low voltage distribution network systems use indirect grounding, that is, small current grounding, and most of the faults are single-phase grounding faults. When a single-phase ground fault occurs, if the fault line is not cut off within the specified time, the fault will expand to two or more points to ground short circuit, thereby forming a phase-to-phase short circuit and even causing system overvoltage, which will damage the equipment and destroy the safe operation of the system. Therefore, it is necessary to Find the fault line and fault point as soon as possible and remove them; and fault line selection is an important prerequisite for a...

AI Technical Summary

Problems solved by technology

The advantage of this type of method is that it uses the characteristic that wavelet analysis is very sensitive to singularity, which makes this type of line selection method more sensitive; the disadvantage is that the result of line selection is easily affected by interference signals

[0006] The above methods are all based on various parameters of current zero-sequence components (current amplitude, phase, power, etc.) to give the results of line selection. However, when a single-phase ground fault occurs, the fault signal is generally very weak and the fault characteristics It is not obvious, which makes it difficult to obtain satisfactory results by conventional methods that only use information such as the magnitude and phase of the current

What is more critical is that after a small current grounding fault occurs, within 1 to 2 hours of faulty operation, the fault signal is not static. Some period signals reflect the fault characteristics and are suitable for line selection, and some period signal interference is not conducive to line selection. This also makes the actual application effect of the fault line selection method based on modern signal processing technology in recent years remains to be seen.

Therefore, the problem of reliable identification of faulty lines with single-phase ground faults in low-current grounding systems has not been satisfactorily resolved.

Images