Partial discharge and aging of AC cable systems under repetitive voltage transient supply

Transients and repetitive transients affect cable insulation life in a way, which is not easily predictable at the design stage. Therefore, cable system life can be shorter than that expected especially when loads controlled by power electronics are fed, or when HVDC systems are integrated in AC networks. This paper has the purpose to provide a statistical approach to estimate the life of a cable insulation system when repetitive transients, of know probability distribution, are expected to affect insulation during operation. It is shown, using the Miner law and a stochastic approach, that life at a given reliability percentage can be shortened even significantly, depending on transient overvoltage and repetition rate. Condition monitoring, however, remains the main tool to keep track of cable health condition during operation life.