Adaptive zero sequence current quick-break protection method

Abstract

The invention discloses an adaptive zero sequence current quick-break protection method, which comprises the following steps of (1) calculating positive sequence reactance XC1, negative sequence reactance XC2 and zero sequence reactance XC0 of a to-be-measured line in real time through microcomputer protection; (2) calculating real-time grounding short-circuit current I0 at a tail end of the lineaccording to the positive sequence reactance XC1, the negative sequence reactance XC2 and the zero sequence reactance XC0 calculated in the step (1) and storing the short-circuit current I0 into a memory RAM; and (3) judging whether line fault current IM measured through microcomputer protection is greater than the real-time grounding short-circuit current I0, stored in real time, at the tail endof the line in the RAM or not, if the judgment result is ''yes'', making a protection device act, or else, returning to the step (1). According to the adaptive zero sequence current quick-break protection method, a fault can be instantaneously removed through the protection device when a short circuit appears in the line, so that the sensitivity of protection is effectively improved.

Description

technical field [0001] The invention relates to the technical field of power supply protection, in particular to an adaptive zero-sequence current quick-break protection method. Background technique [0002] The setting value of the traditional zero-sequence current quick-break protection is calculated according to the setting value of avoiding the single-phase grounding short-circuit current at the exit of the adjacent line. Therefore, the setting value obtained by multiplying the calculated short-circuit current by the setting coefficient Krel cannot Realizing the 0s quick-break protection of 100% of the total length of the line, in the minimum operation mode, will further shorten the protection range of section I, and in some cases may also cause the protection to fail, making the protection range zero. [0003] figure 1 A schematic diagram of the power system, assuming figure 1 The minimum positive sequence reactance X under the operation mode of medium power system C...

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Problems solved by technology

[0016] (1) The setting value is calculated according to the traditional method. Since the setting value is too large, the zero-sequence section I current quick-break protection cannot realize the 0s quick-break protection of 100% of the total length of the line in the maximum operation mode;

[0017] (2) In the minimum operation mode, the protection range of section I will be further shortened due to the increase of the setting value, and in some cases, the protection may be invalidated, making the protection range zero;

However, the zero-sequence current protection is greatly affected by the transformation of the power system operation mode, so the sensitivity is reduced, especially on short-distance lines and complex ring networks, because the protection range of the fast-moving section is too small, or even has no protection range, resulting in zero-sequence current protection. The performance of each section of the current protection is seriously deteriorated, which makes the protection action time very long and the sensitivity is very low

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