Overvoltage spikes transmitted through distribution transformers due to MV spark-gap operation

Small distribution transformers are often protected with spark gaps. As the spark-gap ignites, an overvoltage is coupled to the secondary side due to the steep voltage change. This overvoltage can reach to the customer socket. In this paper, the breakdown of MV spark-gaps is first modeled under an impulse voltage superimposed on AC voltage. To study the overvoltage propagation to the low voltage side, an accurate and simplified high frequency transformer model is used. The model, MV spark-gap and LV network are combined in ATP/EMTP to study the overvoltage spike propagation. Finally, the low voltage surge arrester at the secondary terminals of the distribution transformer is investigated for overvoltage mitigation.