Fault Analysis of The Distance Protection Overreach Caused by The Power Transmission Lines Ring Closing with A Wrong Phase Sequence

摘要

A power transmission lines ring closing with a wrong phase sequence occurred in a regional power grid, which led to an overreach of the line distance protection. Through theoretical analysis, it is found that when the lines ring closing is operated with a wrong phase sequence, the protection shows the similar electrical characteristics as the phase-to-phase short circuit, and there is an equivalent phase-to-phase fault point in the system, which is the midpoint of all equivalent impedances between the power supply on both sides. As a result, the equivalent measured impedance may fall into the action range of the distance protection somewhere, which will lead to the exceeding of distance protection. The actual fault data also confirm the analysis conclusion.