Abstract: In recent years, wildfire accidents in transmission and distribution line corridors have occurred frequently, seriously threatening the stable operation of power grids and presenting a great challenge to fire safety. To study the characteristics of air gap leakage current under the full bridge connection condition of mountain fires on 10 kV distribution lines, discharge characteristic tests of a 12 cm wire-plate gap under different vegetation mountain fire conditions were carried out. The fault signal characteristics of distribution lines were analyzed. The peak characteristics of gap leakage current and gap equivalent impedance under different vegetation mountain fire conditions were experimentally studied. The influence of different capacitive currents on the peak characteristics of leakage current and gap equivalent impedance and on the phase between power frequency leakage current and fault phase voltage was compared. The results show that when the line-to-ground capacitive current increases from 1 A to 3 A, the peak value of leakage current of different vegetation flames decreases. The peak value of leakage current of straw strip flame is most affected by capacitive current, with a drop of 34.8%. Ash content is the main factor affecting gap breakdown under straw strip flame conditions. Under flame conditions, the impedance characteristic of straw flame in the wire-plate gap is inductive, and when cedar branches are in contact with power lines, the tree impedance shows pure resistance characteristics. The research results can provide technical references for warning mountain fires through line electrical signals.

Key words: distribution line, wild fire, capacitive current, electrical characteristics, accident early warning