Effect of Altitude on Lightning Impulse Flashover Voltage of SiR Insulating Material

The Lightning Impulse Flashover Voltage (LIFOV) of outdoor insulators reduces with an increase in altitude which is associated with streamer phenomenon. Among various atmospheric factors such as pressure, temperature and humidity, streamer phenomena are mostly influenced by pressure. In order to carry out the fundamental study, LIFOV of a flat SiR sample is measured at sea level. This measured LIFOV of the test sample at sea level is checked with the Finite Element Method (FEM) based approach using streamer breakdown criteria. LIFOV of the test sample is measured for different altitudes by considering the respective pressures. The atmospheric factors are related to atmospheric electrical conductivity and permittivity and effectively used for the computational studies at high altitudes. Based on the streamer breakdown criteria, LIFOV of the test sample at different altitudes are predicted and verified with measured LIFOV.