Assessment of the backflashover occurrence rate on HV transmission line towers

Abstract

SUMMARY An assessment of the backflashover occurrence rate on the high voltage (HV) transmission line towers is presented in this paper. It is based on a mathematical model that accounts for the transmission line geometry, keraunic level, statistical distribution of lightning current parameters, and correlation between statistical variables defining the lightning current waveshape. Furthermore, assessment of the backflashover occurrence rate on these towers accounts for the tower footing impulse resistance, lightning impulse insulation strength of the insulator strings and surge impedance of the tower itself. Proposed theoretical analysis is backed by the most recent propositions of parameters that define statistical distributions of lightning current parameters and then applied to the typical HV transmission line example. This analysis might be useful when scrutinizing the several first transmission line towers incoming to the HV substations. Hence, here presented analysis could be subsequently applied for the design of the HV substation overvoltage protection. Finally, a sensitivity analysis is provided, in regards to the parameters of the log-normal distributions defining lightning current amplitude and steepness, as well as in regards to the tower footing impulse resistance. Copyright © 2011 John Wiley & Sons, Ltd.