Low and High Voltage Distribution Along a Cap and Pin Insulator String Subjected to AC and Impulse Voltages

Abstract

It is well known that under working ac voltage, the voltage distribution along a cap and pin insulator string is very uneven due to the presence of stray capacitances from the caps to the line conductor and especially to the earthed supporting tower. The ends of the string, particularly that near the line end, are subjected to voltages well above average and this leads to possible interference with radio and television signals especially under wet or polluted conditions, and results in considerable energy loss due to flowing corona currents. The standard way of alleviating this is to fit grading rings at both ends which considerably evens out the voltage distribution so that each cap and pin can be stressed to a higher voltage.