Ageing mechanisms and diagnostics for high voltage bushings — An overview

High voltage bushings play a critical role in the operation of the transformer and when the bushing fails the results can be catastrophic causing considerably collateral damage and posing a risk to safety of personnel. A time-based-maintenance scheme based on manufacturer's manual has already been proved to be not sufficient to recognize rapid degradation of insulation in the high voltage bushing. The initiation of the electrical insulation ageing and breakdown process in high voltage bushings under service condition could not be detected easily and could lead to the sudden failure of the bushing.