A Reduction in the Lightning Induced Overvoltage Amplitude for an Energized MV Power Line with Attached Line Equipment

The Basic Insulation Level (BIL) design of long Medium Voltage (MV) lines was generally based on the nearby lightning performance estimated by models and measurements using floating lines. This resulted in a BIL overdesign that caused more equipment failures due to direct lightning strikes to the line. A methodology whereby the measured polarity of the Lightning Generated Current (LGC) could distinguish between nearby and direct lightning strikes to a long operational line was used to determine the nearby lightning performance of the line. The measurements of this research were compared to the IEEE Std 1410–2010 estimations for a floating line and revealed that the nearby lightning performance of an operational line was much better than for a floating line. This was due to much lower Lightning Induced Overvoltage (LIOV) amplitudes on the operational line compared to a floating line.