Contents 1 Introduction
WILDFIRES near high voltage (HV) transmission lines (TLs) and HV transformer fires are two kinds of HV fires that endanger the safety of power supplies. Wildfires near HV TLs reduce the insulation performance of the TLs and cause them to trip [1], [2]. HV transformer fires burn down the transformers and lead to large area power outages [3]. In recent years, with the construction of China's ultra-HV power grid, HV fires occur frequently. For example, in the spring of 2013, the ultra-HV alternating current ChangNan I TL run by the State Grid Corporation of China (SGCC) shut down three times due to wildfires near TLs. In 2018, the SGCC suffered several fire accidents involving ultra-HV transformers. The streams of water and foam extinguishing agents used in traditional firefighting systems have strong electric conductivity and are unsuitable for suppressing HV electric fires. Suppressing HV electric fires is difficult, due to the fact that it not only requires high fire extinguishing efficiency, but also a high insulation property of the extinguishant [3].
