Variance-based zero-sequence over-current inter-turn protection method for graded controllable reactors

Abstract

The invention discloses a variance-based zero-sequence over-current inter-turn protection method for graded controllable reactors. The method comprises the steps of (1) calculating a variance delta U0 between the zero-sequence voltage of the current cycle of a reactor head end and the zero-sequence voltage of the previous cycle thereof; (2) calculating the variance delta I0 between the zero-sequence current of the current cycle of a control winding side and the zero-sequence current of the previous cycle thereof; (3) on the condition that the variance delta I0 of the zero-sequence current is larger than a zero-sequence over-current threshold delta Iset and the variance delta U0 of the zero-sequence voltage is smaller than a zero-sequence voltage blocking threshold delta Uset, concluding the occurrence of an in-region grounding fault or an inter-turn fault and realizing the inter-turn protection. According to the technical scheme of the invention, on the basis of the zero-sequence current variance on the same control winding side, the amplitude of the line-side zero-sequence voltage variance is compared to judge the inter-turn fault of a reactor load on the control winding side of the reactor. In this way, during the occurrence of an inter-turn fault on the control winding side of a graded controllable high-voltage shunt reactor, the reactor is prevented from being affected by the influence of the incomplete-phase operation and other operating states based on the zero-sequence over-current protection means. Meanwhile, the method is simple and concise in criterion, sensitive in protection and high in reliability.

Description

technical field [0001] The invention belongs to the technical field of electric power system relay protection, and in particular relates to a zero-sequence overcurrent turn-to-turn protection method for variable amount of graded controllable reactors, which has a high degree of inter-turn short-circuit fault of load reactance on the control winding side of the graded controllable reactor protection sensitivity, reliability and adaptability. Background technique [0002] In high-voltage long-distance transmission lines, in order to suppress power frequency overvoltage and compensate line capacitive current, high-voltage shunt reactors are generally configured. Traditional fixed-capacity reactors, because the capacity cannot be adjusted, limit the application effect of the reactor. Therefore, in order to adapt to the adjustment of the reactor, the graded controllable reactor is used, which can better adapt to the operating state of the line. It plays a better optimization rol...

AI Technical Summary

Problems solved by technology

Due to the zero-sequence overcurrent protection with zero-sequence voltage blocking, the overcurrent setting is generally low and the sensitivity is high. However, when the line is not in full-phase operation, the zero-sequence voltage blocking fails, and the zero-sequence overcurrent protection is blocked. The control winding side Turn-to-turn fault of load reactor cannot be protected

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