The response characteristics of 10 kV typical distribution transformers under high-altitude electromagnetic pulse

High-altitude electromagnetic pulses (HEMP) have the potential to inflict substantial harm on the distribution system through coupling with overhead lines. This study investigates HEMP-induced conduction effects on 10 kV distribution transformers through theoretical analysis and test validation. Transmission line theory was employed to analyze the coupling environment of overhead lines under HEMP. To evaluate transformer response characteristics to these conducted disturbances, a comprehensive test system was established, comprising both simulation models and physical test platforms. The response characteristics of the transformers and the distribution pattern of winding voltages were finally determined. The results show that the 10 kV distribution transformer exhibits a damage threshold at 267.5 kV. There is significant non-uniform voltage distribution across the transformer winding with Up_max = 164.3 kV and ΔUp_max = 78.8 kV. Both maximum values occur at the first turn position, indicating this region as the most probable initiation site for insulation breakdown due to concentrated dielectric stress.