Main transformer and high voltage side cable zero-sequence differential protection polarity test circuit and method

Abstract

The invention discloses a main transformer and high voltage side cable zero-sequence differential protection polarity test circuit and method. According to the test circuit, a maintenance power supply is connected when a main transformer and a high voltage side bus are in the stop state, a single-phase voltage regulator is regulated and current is outputted to the appropriate value so that a current loop composed of the maintenance power supply-single-phase voltage regulator TT-isolation transformer TI-ammeter-main transformer high voltage side Y-shaped three-phase windings-main transformer high voltage side cable-main transformer high voltage side line knife Q9-GIS circuit breaker Q0-primary female knife Q1 (or secondary female knife Q2)-primary female grounding knife QG1 (or secondary female grounding knife)-grounding network-ground is formed. The current flows through the primary side of the first zero-sequence current mutual inductor ZCT1 and the second zero-sequence current mutual inductor ZCT2 of a zero-sequence differential protection device 87GMC so that simulation of zero-sequence current of the primary system in case of external grounding fault can be realized, and the polarity of the main transformer and the high voltage side cable zero-sequence differential protection device can be tested and inspected by the loop current.

Description

technical field [0001] The invention relates to a polarity test circuit and a test method for a main transformer and a high-voltage side cable zero-sequence differential protection polarity test circuit, and is suitable for the situation where the installation distance of ZCTs on both sides of the main transformer and the high-voltage side cable zero-sequence differential protection is relatively long. Background technique [0002] Main transformer and high-voltage side cable zero-sequence differential protection device 87GMC is used as the main protection when the main transformer high-voltage side Y-shaped winding and high-voltage side cables are grounded. With the characteristics of high ground fault sensitivity and fast action speed, the protection operates in 0 seconds when the unit stops completely, that is, trips the GIS circuit breaker on the high voltage side of the main transformer, the low voltage side switch of the plant general transformer, the magnetic field swi...

AI Technical Summary

Problems solved by technology

The polarity test of the zero-sequence differential protection device is a troublesome problem, because when the generator G-main transformer MTR unit is in normal operation, there is only positive sequence current in the primary circuit of the protected equipment (main transformer and high-voltage side cable). , there is no zero-sequence current, so the load current cannot be used to verify the correctness of the polarity of the zero-sequence differential protection device

However, if the polarity test of the zero-sequence differential protection device of the main transformer and the high-voltage side cable is not carried out, accidents of tripping due to the wrong polarity of the zero-sequence differential protection device will often occur when the external system has a ground fault, resulting in economic loss

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