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A Method of Starting Criterion for UHV DC Line Protection

An ultra-high voltage DC, line protection technology, applied in the direction of measuring current/voltage, measuring devices, instruments, etc., can solve the reduction of the voltage change rate, the change rate of the directional traveling wave is affected by the transition resistance, the voltage variable and the ground mode wave faults issues of distance

Active Publication Date: 2011-12-14
KUNMING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, according to the relevant data of actual operation at home and abroad, the currently used DC line traveling wave protection (mainly provided by ABB and SIEMENS) is affected by the existence of smoothing reactors and DC filters at the end of the line, resulting in voltage changes rate reduction; voltage variables and ground mode waves are affected by fault distance; directional traveling wave change rate is affected by transition resistance, etc.
It is precisely because of the existence of these influencing factors that sometimes the existing DC protection device will refuse to operate.

Method used

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  • A Method of Starting Criterion for UHV DC Line Protection
  • A Method of Starting Criterion for UHV DC Line Protection
  • A Method of Starting Criterion for UHV DC Line Protection

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Experimental program
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Embodiment Construction

[0042] Simulation model such as figure 1 As shown, a positive ground fault occurs at a distance of 100km from the protection installation, the fault transition resistance is 0.1Ω, the time window length is 5ms, and the sampling frequency is 10kHz.

[0043] (1) After the DC line fails, the polar wave of the positive line is obtained according to the pole line voltage and the pole line current at the measuring end

[0044] (1)

[0045] In the formula, is the polar wave impedance, is the pole-to-line voltage, is the polar current, n=1, 2, 3…. N , N= 50 is the sampling sequence length;

[0046] (2) Use the db4 wavelet of the Daubechies wavelet system to perform one-dimensional wavelet decomposition on the polar wave voltage to obtain the modulus maximum value K m =625;

[0047] (3) According to the starting criterion K m =625> Kset , to enable the element to start.

[0048]

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Abstract

The invention discloses a criterion method for the protection startup of an extra-high voltage direct-current circuit according to a polar wave change rate. The method comprises the following steps of: when the direct-current circuit fails, determining a polar wave according to direct-current voltage and current measured at a protection installation position, wherein the sampling rate is 10 kHz and the time window is 5 ms; performing one-dimensional wavelet decomposition on the polar wave by using a db4 wavelet of a Daubechies wavelet system to obtain modulus maximums, and selecting a first modulus maximum serving as a voltage change rate startup criterion, wherein the electric quantity used by the criterion has high polar wave representation discrimination and is easy to judge; and performing one-dimensional wavelet decomposition on a fault signal by using the db4 wavelet of the Daubechies wavelet system, so that the influence of noise can be eliminated to a great extent. As proved by a large quantity of emulation results, the criterion method has a good effect.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a method for using the polar wave change rate as the starting criterion for UHV DC line protection. Background technique [0002] At present, how to improve the safety and reliability of DC line operation has become an urgent problem to be solved. Whether the DC line fault can be correctly judged is the key to DC line protection. At present, traveling wave protection is widely used in the world as the main protection of high-voltage DC line protection. Its fast single-ended protection is based on the sudden change of voltage traveling wave, the rate of change of voltage traveling wave and the gradient of current change as criteria. It has ultra-high-speed action characteristics, and is not affected by current transformer saturation, system oscillation and long-term distributed capacitance. However, according to the relevant data of actual operation...

Claims

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Application Information

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IPC IPC(8): G01R19/165
Inventor 束洪春田鑫萃张广斌孙士云刘可真张毅
Owner KUNMING UNIV OF SCI & TECH
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