High voltage DC power line - has polarity of cables periodically reversed to change voltage stress and prevent insulation breakdown

摘要

The DC power cable transmits power at high voltage and is intended for use in deep water or underground. Breakdown in the dielectric or insulator due to local voltage stress and heating effects are minimised. The parallel insulated lines making up the cable conductors are connected to switches at each end of the cable. Switching, which occurs at periods between one and one hundred hours, is arranged such that each line experiences a change of voltage stress while maintaining the overall level of transmitted power. An auxiliary AC or DC level is injected into each line at the moment its potential moves through zero.