Abstract
When one loop line of the multi-circuit transmission lines on the same tower is in states of non-full-phase operation or asymmetric line-breaking faults, the zero-sequence direction of functioning loop lines is likely to maloperation due to zero-sequence voltage compensation. The multi-circuit transmission lines on the same tower with different voltage classes will induce the same zero-sequence voltage distribution trend as the fault line due to the mutual inductance between loop lines, and thus may conduct improper operation as well. This paper analyses the causes of maloperation of zero-sequence directional protection caused by non-full phase operation or line-breaking fault of multi-circuit lines on the same tower, and puts forward a method to prevent maloperation by extracting line status from station domain information. In the case of multi-circuit lines on the same tower with same voltage class, the crossing point of zero-sequence voltage of the line can be calculated and the zero-sequence voltage can be compensated in reverse to prevent maloperation. In the case of multi-circuit lines on the same tower with different voltage class, fault characteristics can be identified according to substation information and the zero-sequence direction protection can be automatically blocked. RTDS is used to simulate and verify the electrical characteristics, malfunction process and the effectiveness of prevention methods of multi-circuit lines on the same tower when a non-full-phase operation or abnormal line breakage occurs.
Published Version
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