The maloperation of common variable ratio differential protection caused by the main transformer zero sequence CT disconnection

Huadian Technology ›› 2018, Vol. 40 ›› Issue (6): 26-27.

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The maloperation of common variable ratio differential protection caused by the main transformer zero sequence CT disconnection

Huaneng Tongchuan Zhaojin Power Plant, Tongchuan 727100, China

Published:2018-06-25

Abstract

Abstract:

It analyzes an accident due to the disconnected point of zerosequence CT circuit of a main transformer on the power plant side. When a singlephase ground fault occurs outside the grid side zone, it leads to a utility variable ratio differential protection. It reveals that if there is disconnected point in a zerosequence CT secondary side, the induced secondary high voltage may affect the adjacent AC sampling loop. Analyzing the typical wave characters of this accident, specific preventive measures are put forward as references for the unknown accident.

Key words:

transformer ;RCS985, maloperation of protection, zerosequence CT open circuit, outofzone fault, variable slope ratio differential

ZHANG Xuefeng.

The maloperation of common variable ratio differential protection caused by the main transformer zero sequence CT disconnection

[J]. Huadian Technology, 2018, 40(6): 26-27.

The maloperation of common variable ratio differential protection caused by the main transformer zero sequence CT disconnection

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