Influence of the typical vegetation ashes/particles on discharge characteristics of conductor-plane air gap

The frequent forest fires become a serious threat to the performance of transmission lines’ external insulation, and large quantities of smoke (carbon black) and flying ashes are produced during the combustion of vegetation, reducing the dielectric strength of the air gap drastically. In order to study the effect of the typical vegetation ashes on the discharge characteristics of conductor-plane air gap, experimental studies were carried out with vegetation fire simulation test platform in this study, and typical vegetation ashes of thatch, straw and fir branch were collected. The simulation model was built to analyse the influence mechanism of multiple particles on the breakdown characteristics. It shows that the existence of particles make the electric field distribution between conductor and plane non-uniform, the maximum electric field strength near the elongated particle is 10.2 times as much as the background electric field, and the maximum electric field strength of the gap increases by about 55.7%, when the length of the elongated particle changing from 15 to 25 mm; the particle with larger relative dielectric constant and smaller distance from the simulation conductor, has the greater electric field distortion degree