Analysis of pilot zero-sequence directional protection mal-function in double-circuit lines break-conductor fault and solutions

When asymmetric break-conductor faults occur in double-circuit transmission lines, the shift of load may produce large unbalance current in healthy line, leading to the malfunction of pilot zero-sequence directional protection with voltage compensation. This paper discusses the zero-sequence character of double-circuit lines in break-conductor fault, presents the malfunction mechanism of pilot zero-sequence directional protection with voltage compensation in healthy line after single-phase grounding fault tripping. The theoretical analysis was confirmed through simulation model. Moreover, preventive measures based on one-end single line or double lines electrical information was proposed.