Prospect of voltage uprating of a conservatively designed EHV transmission line

Abstract

Voltage uprating of existing overhead lines provide a useful method to tackle increasing power demands under present circumstances, where there is growing opposition to the construction of new power transmission installations. In the past, voltage uprating techniques have been applied to lines formerly intended to operate up to 275kV, but there is an incentive to examine the prospect of uprating lines of even higher voltages which have been designed conservatively with deterministic procedures. This paper explores the prospect of voltage uprating of an existing 500kV double-circuit overhead transmission line in Pakistan. The study includes statistical evaluation of line insulation under switching overvoltages, lightning and pollution together with assessment of corona effects and low frequency electric and magnetic fields. It has been shown that voltage uprating of the studied line to 735kV is achievable whilst satisfying performance criteria.