A working criterion method for line selection device for comparison of power frequency variation amplitude
A technology of power frequency variation and line selection device, applied in the direction of fault location, etc., can solve the problems of large interference influence and large judgment error, achieve high precision, ensure correct judgment, and improve the effect of anti-interference ability
Active Publication Date: 2015-12-02
SHANDONG ELECTRIC POWER ENG CONSULTING INST CORP
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Problems solved by technology
However, the traditional extraction method of zero-sequence current power frequency variation is greatly affected by interference, and the judgment error is large
[0005] In the journal-Sichuan Electric Power Technology, 2007, Volume 30, Issue 6, the paper [Research on the Single-phase Grounding Line Selection Method of the Neutral Point Ungrounded System], proposed a method to judge the fault line by the amplitude, but in the article The power frequency change is the traditional zero-sequence current power frequency change extraction method, so it is greatly affected by interference and the judgment error is large
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[0018] Example: assume that phase a of the output line L1 is single-phase grounded.
[0019] Before grounding occurs, the voltage transformer TV zero-sequence voltage U 0 is equal to zero, u set The setting of is prior knowledge. The current transformer TA of the three output lines L1, L2, L3 forms a zero-sequence current are theoretically equal to zero. Due to the interference in the power system and the error in the current transformer, the magnitude of the power frequency change is compared with the zero-sequence current calculated by the working criterion of the line selection device are not equal, and are not equal to zero, so the calculated zero-sequence current is the actual composite error.
[0020] After the ground fault occurs, the voltage transformer TV zero sequence voltage U 0 ≥U set , the power frequency variation amplitude comparison line selection device can judge that there is a ground fault at this time, but it cannot determine which output line...
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The invention relates to a working criterion method for a one-phase grounding power frequency variation amplitude comparison line selection device. According to the working criterion method, an interference influence is small, and precision and sensitivity are high. The method comprises the following steps: enabling zero-sequence currents of all electric transmission lines and a zero-sequence voltage at the bus position to be sent into the power frequency variation amplitude comparison line selection device; comparing the size of power frequency variation zero-sequence current amplitudes of all electric transmission lines through the power frequency variation amplitude comparison line selection device, wherein the electric transmission line with the largest amplitude is a faulty line; and taking sampling values of power frequency cyclic wave with the number of M of zero-sequence currents in the transmission lines for power frequency variation zero-sequence currents to calculate; when 3<M<20, taking k=0; and when U0>= Uset, taking k> (Mw+Dw), D>3.
Description
technical field [0001] The invention relates to the field of relay protection of electric power systems, in particular to a method for working criteria of a line selection device for comparing the magnitude of a single-phase grounding power frequency change in a neutral point ungrounded system and a neutral point resistance grounding system. Background technique [0002] When a single-phase ground short circuit occurs in a power system where the neutral point of the power transformer is not grounded, there is no short circuit circuit and no short circuit current will be generated. The relay protection of the power system does not need to trip, and the power system is allowed to continue to run for a period of time. But single-phase grounding is also harmful to the power system. Therefore, when a single-phase ground short circuit occurs in this kind of system, the relay protection must send out an alarm signal, and the operator on duty will make corresponding treatment, and f...
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IPC IPC(8): G01R31/08
Inventor 于青王东周建许卫东樊潇孙明冬郑春强张洪霞
Owner SHANDONG ELECTRIC POWER ENG CONSULTING INST CORP