Adaptive discrimination method for zero sequence protection direction of distribution line

Abstract

The invention relates to the technical field of circuit protection, and more specifically relates to an adaptive discrimination method for the zero-sequence protection direction of a distribution line. The adaptive discrimination method comprises the steps of inputting a CT polarity automatic detection function when the distribution line is put into operation with load, comparing the phase difference between phase current Ip and phase voltage Up of a three-phase CT, carrying out comparison with a manually set load current direction, judging the polarity of the CT, automatically reversing the polarity of the three-phase CT if the polarity of the CT is reversed, quitting the CT polarity automatic detection function and the load current direction after the line is put into operation; comparing the phase difference between self-generating zero-sequence voltage 3U0 and self-generating zero-sequence current 3I0 when a grounding fault occurs in the line, and discriminating the zero-sequence protection direction according to the phase difference. The adaptive discrimination method can avoid a problem of low zero-sequence current measurement accuracy caused by a too small secondary value ofthe self-generating zero-sequence current. The zero-sequence protection direction discrimination adopts the self-generating zero-sequence current and self-generating zero-sequence voltage, and the three-phase CT has already verifies the polarity when being loaded, thereby effectively avoiding the risk of failure to operate due to the reversed polarity connection of the zero-sequence CT.

Description

technical field [0001] The invention relates to the technical field of circuit protection, in particular to a method for self-adaptive discrimination of the zero-sequence protection direction of distribution lines. Background technique [0002] The neutral point grounding mode of 10kV~66kV power distribution system is closely related to power supply reliability, overvoltage and insulation coordination, relay protection, etc. It is an important condition to ensure the safe, reliable and stable operation of people, equipment and power systems. At present, the neutral point grounding methods are widely used in the power distribution system as follows: (1) the neutral point is not grounded; (2) the neutral point is grounded through the arc suppression coil; (3) the neutral point is grounded through the small Resistance grounding method; (4) The neutral point is grounded in parallel with a small resistance through the arc suppression coil; (5) The grounding method of the fault ph...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art, provide an adaptive discrimination method for the zero-sequence protection direction of distribution lines, and solve the risk of refusal to operate due to reverse polarity of the external zero-sequence CT of the distribution line

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