Method for automatically switching power frequency protection fixed values

Abstract

The invention relates to a method for automatically switching power frequency protection fixed values. A power frequency component ID_fund of DC current in a DC circuit of a deicing device is utilized to form over power frequency protection; the power frequency protection adopts two high and low fixed values; initially the high fixed value is adopted; when a converter value of the deicing device is unlocked, and the sudden decrease of a power frequency component UD_fund of DC voltage in the DC circuit of the deicing device and the sudden increase of the ID_fund occur simultaneously, the high fixed value is adopted; the low fixed value is adopted when the sudden decrease of the UD_fund and the sudden increase of the ID_fund do not occur simultaneously; and a difference value of the high fixed value and the low fixed value is the value of the current inducted in a deicing circuit when parallel circuits work normally. The method can effectively judge whether the DC deicing circuit is normally inducted by other AC circuits distributed in parallel on the same tower to generate the power frequency components so as to automatically switch the two high and low fixed values of the power frequency protection, avoid false operation of the power frequency protection and not to reduce the sensitivity of the power frequency protection for a single circuit or an equivalent signal circuit.

Description

technical field [0001] The invention relates to a method for automatically switching power frequency protection fixed values ​​and a device using the method. Background technique [0002] Icing of transmission lines in winter seriously threatens the safe operation of the power system. The successful development of the DC ice melting device has played a huge role in improving the power grid's ability to resist ice disasters. The basic principle of the DC ice-melting device is to use a converter valve to convert the AC current into a DC current, inject it into the AC wire, and use the DC current to generate heat in the wire resistance to melt the ice. [0003] When the converter valve loses the pulse fault, it will cause a large power frequency component in the DC ice melting current. The existing method for detecting the pulse loss fault of the converter valve is to detect the power frequency component in the DC current, and protect the pulse loss fault of the converter val...

AI Technical Summary

Problems solved by technology

[0007] Insufficiency of the existing judgment method: When the DC ice melting device melts ice on one of the double-circuit or multi-circuit AC lines paralleled on the same pole, the parallel lines will also be induced in the ice-melting AC lines. Larger AC current, so it is not easy to distinguish the pulse loss of the converter valve in the ice melting device or the normal induction of the parallel line, which may easily cause the power frequency protection (also known as 50Hz protection in China) of the ice melting device to malfunction

However, when the ice-melting line is a single-circuit line or an equivalent single-circuit line, the increased current setting will reduce the sensitivity of power frequency protection

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