Analysis of a relay operation for an intercircuit fault

During a winter snowstorm, a large amount of snow fell across a fairly small region in the Midwest of the United States. The temperatures and wind conditions were such that the snow accumulated vertically on transmission lines in the affected area, leading to large line sags in the transmission and subtransmission systems. Shortly after the snow accumulation ended, the temperatures warmed rapidly, causing the snow to melt. As large sections of snow fell off the underbuild subtransmission line, the subtransmission line came in contact with the transmission line above, creating an intercircuit fault. An intercircuit fault is a rare fault type in which phases from two circuits sharing the same right of way come in contact with each other. In this paper, we use gathered event reports to analyze an intercircuit fault that occurred multiple times between two separate voltage levels after the snowstorm. We also provide a detailed analysis of the mho element behavior for this fault and investigate the performance of different mho element polarizing techniques. The performance of the directional element and impedance-based fault location is examined. Furthermore, symmetrical components are used to verify the fault current and voltages for this intercircuit fault. Improvements to relay performance during intercircuit faults, including line current differential, are discussed.