A method for setting the value of zero sequence inverse time overcurrent protection of extra-high voltage AC line

Abstract

A method for setting the zero-sequence inverse-time overcurrent protection for ultra-high voltage AC lines includes: determining the zero-sequence inverse-time current setting while ensuring sensitivity during high-resistance grounding faults; determining the zero-sequence inverse-time time setting based on the high-resistance grounding fault clearing time requirements and the fault current change action time gradient requirements; calculating the minimum withstand zero-sequence current for the grounding distance protection (section III) of each line in the entire network, taking the maximum value of the minimum withstand zero-sequence current for all lines in the network, and determining the minimum turning current of the zero-sequence inverse-time protection; determining the coordination time setting based on the set zero-sequence inverse-time current setting, the zero-sequence inverse-time time setting, and the minimum turning current; and determining the minimum time setting of the zero-sequence inverse-time overcurrent protection based on the three-phase inconsistency protection action time, reclosing time, the final stage action time of the grounding distance protection, and the coordination time setting. This design not only simplifies the setting method but also improves its reliability.

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