Fault diagnosis method and related device for capacitor cut-out system

Abstract

This application discloses a fault diagnosis method and related devices for capacitors cut out of the system. Since the voltage waveform amplitude of the three-phase terminals of the capacitor is basically kept in a stable state, and it is always kept three-phase with the neutral point potential when no fault occurs. Relatively symmetrical relationship, so when the capacitor is switched off and exits the system, judge whether the capacitor is faulty according to the voltage at the three-phase load terminal of the capacitor; if the capacitor is faulty, remove the high-frequency harmonic component and the DC component of the three-phase load terminal voltage correction , calculate the correction amount of the three-phase load terminal voltage according to the average value of its envelope curve, and set the phase with the largest correction amount as the fault phase; then judge the current direction of the determined fault phase capacitance; finally, according to the current of the fault capacitor bridge arm The direction determines the specific fault bridge arm capacitance, so that when the internal fuse protection and bridge differential current protection cannot operate normally, it can diagnose whether the capacitor is in a fault state, and diagnose the specific fault location of the capacitor.

Description

technical field [0001] The present application relates to the technical field of capacitor fault diagnosis, and in particular to a fault diagnosis method and a related device for a capacitor cut-out system. Background technique [0002] The state of capacitors in substations plays a key role in the operation of the grid system. Traditional shunt capacitors generally adopt internal fuse protection as the main protection and bridge current differential protection as backup protection, but there are major defects. [0003] When the capacitive element breaks down, the internal fuse is blown by overcurrent, thereby isolating the faulty capacitive element. When the breakdown of parallel capacitive elements reaches a certain number, the internal fuse cannot normally isolate the fault, resulting in a short circuit accident in the entire string. Furthermore, when the capacitor fails, the current flowing through the bridge difference current transformer is relatively large, which may...

AI Technical Summary

Problems solved by technology

Traditional shunt capacitors generally use internal fuse protection as the main protection and bridge current differential protection as the backup protection, but there are major defects

[0003] When the capacitive element breaks down, the internal fuse is blown by overcurrent to isolate the faulty capacitive element. When the breakdown of parallel capacitive elements reaches a certain number, the internal fuse cannot normally isolate the fault, resulting in a short circuit accident in the entire string

Furthermore, when the capacitor fails, the current flowing through the bridge difference current transformer is relatively large, which may easily cause damage to the transformer, and it is impossible to judge the occurrence of the fault normally, and the probability of malfunction and refusal is relatively high

Even if the capacitor in normal working state exits the system through the opening of the circuit breaker, an overvoltage will be generated on the first open phase to threaten the insulation of the capacitor. When the circuit breaker is closed, the inrush current and overvoltage will cause more serious insulation damage to the capacitor.

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