Evaluation of K-Factor Based on Insulation Characteristics under Non-Standard Lightning Impulse Waveforms

The IEC, which defines the lightning impulse test methods for electric power equipment, is about to introduce the K-factor method for evaluating overshoot of lightning impulse waveforms. There is an urgent need to examine the K-factor method using such parameters as the types and sizes of insulating media and structures. This paper evaluates the K-factor method in the "High-Voltage Test Techniques" using the insulation characteristics of overshoot waveforms in non-standard lightning impulse waveforms. The insulation elements of oil-immersed transformers and gas-insulated switchgear (GIS) used in this study are oil gaps, turn-to-turn insulations, and gas gaps (field utilization factor eta = 0.45 and 0.60), all of which showed results close to the proposed K-factor curve.