Lightning Impulse surface flashover Voltage – Time (V-t) characteristics of spacers with conducting particle on its surface under compressed gases

The presence of spacers reduces the impulse strength in comparison with plain air gaps. The flashover ratios are found to vary between 0.9 to 0.4 for the pressure range 100 to 500 kPa. Even with a minute conducting spot, impulse breakdown strength were found to decrease substantially for the pressure range investigated. Surface discharges were observed to form carbonized tracks on the surface of insulator even with minute conducting spot on spacer surface. Spacer with wire particles has shown maximum reduction in breakdown strength as compared to either spherical or fine conducting spot of silver paint. Studies in non-uniform fields indicate that the breakdown voltage is influenced by gas pressure, location of particle and polarity of the impulse voltage. The relative dimensions of the…