A Countermeasure of Simultaneous Double Circuit Trip of 154 kV Transmission Line by Lightning Current

摘要

It has been reported that more than 60% of transmission line faults occurs due to lightning strokes. To protect transmission lines from lightning stroke, reduction of tower footing resistance, multiple ground wires and unbalanced insulation in double circuit lines, have been generally considered. In Korea Electric Power Corporation most of transmission lines are double circuit transmission lines. At summer peak load, there are many simultaneous double circuit trips in KEPCO. The general method is often not effective to prevent the simultaneous trip faults. And we have found out that to attach parallel line arrester in the insulator string of the one circuit is the best way to eliminate the double circuit trip. We installed 90 line arresters in a 154 kV double circuit line. The air gap of a line arrester is 630 mm whereas the arcing horn gap of insulators string of 154 kV transmission line is 1120 mm. By EMTP simulation, lightning discharge current follows through the line arrester in a few to 10s microseconds and extinguished. After a few years' operation, there is no double circuit trip in the line arrester installed section.