Anti-maloperation Study of Zero-sequence Directional Protection for Three Circuits on the Same Tower

Based on the limitation of zero-sequence voltage compensation of traditional zero-sequence directional protection principle, an improved anti-maloperation protection strategy is proposed. First of all, by analyzing the characteristics of zero-sequence component, zero-sequence protection principle and maloperation reason of three circuits on the same tower, it is found that zero-sequence voltage over-compensation will change the polarity of zero-sequence voltage and lead to protection maloperation. Considering that the negative-sequence components are not affected by the mutual inductance between lines, a method of introducing negative-sequence components and reducing compensation impedance is proposed, which can reduce the possibility of over-compensating greatly. Based on this, the improved zero-sequence directional protection anti-maloperation logic is constructed. When a longitudinal fault occurs on the line, this method can achieve the purpose of preventing maloperation accurately. Finally, the effectiveness and feasibility of the proposed method are verified by numerical simulation.