Field Measurement of Switching Surges on Unterminated 345-Kv Transmisson Lines

Field measurements are presented for switching surge line-to-ground voltages at both bus and receiving ends of unterminated 345-kv transmission lines of intermediate length, when energizing and re-energizing. Varied and representative configurations were studied. Effects of source configuration and breaker-pole closing sequence and prestriking are demonstrated. An estimate of overvoltage probability is attempted as well as a rationalized description of waveforms. Comparison tests on 138-kv lines were conducted, and data presented therefrom.