Method for fault line selection of electric distribution network by using S transformation energy relative entropy

Abstract

The invention relates to a self-adaptive method for single-phase grounding fault line selection of an electric distribution network by using S transformation energy relative entropy. The method comprises the following steps: when the zero-sequence voltage instantaneous value of a bus is out of limit, starting a fault line selection device immediately; performing S transformation on zero-sequence current in 1 / 4 cycle after the fault of each line, and calculating transient energy under each frequency of the zero-sequence current of each line by using a complex matrix obtained by the S transformation; and calculating the S transformation energy relative entropy under each frequency of each line and solving the comprehensive S transformation energy relative entropy of each line by using the super-strong recognition capability of the relative entropy to slight differences between signals, and self-adaptively selecting out the fault line by comparing the size of the comprehensive S transformation energy relative entropy of each line under all frequencies. Theoretical analyses and a large number of emulations show that the method effectively avoids the influence caused by a CT saturation discontinuous angle on the line selection, and is applicable to the cable-wire mixed line, pure cable lines and pure aerial lines.

Description

Technical field: [0001] The invention relates to a fault line selection method of a power distribution network by using S transformation energy relative entropy, which belongs to the technical field of electric power system relay protection. Background technique: [0002] When a single-phase ground fault occurs in the resonant grounding system, the line voltage is still symmetrical and the fault current is small, and it can continue to run for 1 to 2 hours, which is conducive to improving the reliability of power supply. However, the non-fault relative ground voltage rises, and long-term operation will easily cause the fault to expand into two or more short circuits; arc grounding will also cause overvoltage in the entire system, endangering the insulation of the equipment and the safe operation of the system, so the fault must be determined in time Line, troubleshoot as soon as possible. However, the grounding phenomenon of the resonant grounding system is very complicated...

AI Technical Summary

Problems solved by technology

The line selection method based on steady-state quantities is easily affected by transition resistance and unstable arc, has low sensitivity, and is prone to misjudgment; the signal injection method uses the method of injecting external signals into the system for line selection, but there are obvious shortcomings: ① When the ground is high-impedance, the injected signal is weak and difficult to detect; ②When the arc is grounded, the harmonic content is rich, and the injected signal is easily disturbed

③The applicable voltage level is low (usually 10kV), and the workload of operation and maintenance is relatively large

When a single-phase grounding occurs in a resonant grounding system, the discharge of the faulty phase capacitor and the charging of the non-faulty phase capacitor will generate a transient current whose amplitude is several to dozens of times larger than the steady state value. The line selection method based on the transient quantity has high sensitivity and The influence of the arc suppressing coil is small, but the effect of line selection of the existing methods is mostly unsatisfactory, mainly because the protection desire of line selection is not large, and the accuracy and reliability are low

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