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Negative sequence reactance direction judging method

A negative-sequence reactance and direction determination technology, applied to electrical components, emergency protection circuit devices, etc., can solve problems such as small negative-sequence voltage, wrong direction determination, and unsatisfactory sensitivity

Inactive Publication Date: 2009-10-21
DONGFANG ELECTRONICS
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  • Summary
  • Abstract
  • Description
  • Claims
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Problems solved by technology

The disadvantage of this method is that for some asymmetrical faults in some systems, the negative sequence voltage may be small, and the sensitivity cannot meet the requirements, resulting in wrong direction judgment

Method used

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Embodiment Construction

[0018] The present invention will be described in further detail below in conjunction with the accompanying drawings.

[0019] refer to figure 1 , there is a protective device on the m side. The protection device of the line has the function of data processing, which can sample the three-phase voltage and current of this side, and control the actuator of this side. The protection device samples the three-phase voltage and current on the local side, calculates the negative sequence reactance, and then performs direction discrimination.

[0020] figure 2 , image 3 They are the negative-sequence network diagrams when forward and reverse asymmetrical faults occur, respectively. An asymmetrical fault occurs at point F on the line powered by both sides of the power supply. In the figure, z sm ,z sn are the negative-sequence source impedances on both sides of the line, Z L2 is the negative sequence line impedance, is the negative sequence potential at point F, is the neg...

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Abstract

The invention discloses a negative sequence reactance direction judging method for judging fault direction when asymmetrical faults occur in systems, comprising the following steps: a protective device is installed at a side of a protected line section, and the negative sequence reactance is obtained by calculating negative sequence voltage phasor *2 and negative sequence current phasor *2 at the side, and calculating the negative sequence impedance *2 / *2, and then getting the imaginary part thereof, X2=Im(*2 / *2); and the directions of asymmetrical faults are distinguished according to the size relationship between the negative sequence reactance and fixed value. The directional element has high flexibility without setting voltage threshold; and the direction still can be accurately judged even if the sensed negative sequence voltage has small amplitude.

Description

(1) Technical field [0001] The invention relates to the field of relay protection of electric power systems, in particular to a fault direction determination method. More specifically, it is a method for judging the direction of the fault when the AC transmission line of the power system fails. (two), background technology [0002] In order to ensure selectivity, directional elements are configured in line protection. Negative sequence directional elements are widely used, and are used to distinguish the fault direction when asymmetrical faults occur in the system. The current negative-sequence directional element generally detects the angle between the negative-sequence voltage and the negative-sequence current. If the angle is within a certain range, it is judged as forward or reverse. The disadvantage of this method is that for some asymmetric faults in some systems, the negative sequence voltage may be very small, and the sensitivity cannot meet the requirements, result...

Claims

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Application Information

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IPC IPC(8): H02H7/26
Inventor 刘凯李蔚王雪梅孙建波王玲
Owner DONGFANG ELECTRONICS
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