An Adaptive Differential Protection Method

Abstract

The invention relates to an adaptive differential protection method, which comprises the steps that a line protection device performs sampling and filtering to voltage and current waveforms of a transformer; information such as current and voltage on the two sides of a line is exchanged through communication; current I<phi m> and I<phi n> (wherein phi=A, B and C which respectively stand for three phases of the power transmission line; m and n stand for the two sides of the line, similarly hereinafter), voltage U<phi m> and U<phi n>, zero-sequence current I<0m> and I<0n> and zero-sequence voltage U<0m> and U<0n> of the two sides of the line are obtained through calculation; proportional brake differential protection, composite differential protection and longitudinal differential protection are formed; the proportional brake differential protection, the composite differential protection and the longitudinal differential protection are combined to form the adaptive differential protection. The adaptive differential protection method provided by the invention has the characteristics of high sensitivity, wide application scope and no setting. The adaptive differential protection method has the advantages that the sensitivity to short-circuiting in the original differential protection can be improved, the action can be sensitively performed when the angle difference of the system equivalent impedance of the two sides of a fault point is great (such as under the situation that current phase reversion occurs in the power transmission line with serial compensation capacitors), the quick action can be realized during oscillation and the fixed value of the original differential protection is not increased.

Description

technical field [0001] The invention belongs to the field of power systems, and more specifically relates to a method for relay protection. Background technique [0002] In EHV transmission lines, optical fiber differential protection has been widely used as the main protection. [0003] The principle of optical fiber differential protection is advanced, and the typical differential criterion is the proportional braking differential protection based on "phasor sum" and "phasor difference". (For example, the current reverse phase occurs in the transmission line containing series compensation capacitors), or when an internal fault occurs during oscillation, the current angle difference on both sides of the line is an obtuse angle or even a flat angle, which will affect the typical proportional braking differential protection criterion sensitivity. [0004] How to better improve the performance of differential protection needs to be studied. Contents of the invention [00...

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Problems solved by technology

[0005] In order to solve the problem that the typical proportional brake differential protection based on "phasor sum" and "phasor difference" may refuse to operate due to the angle difference of the current on both sides of the line being an obtuse angle or even a flat angle when there is an internal fault in the transmission line. The invention discloses an adaptive differential protection method

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