The Impact of System Voltage on the Ageing of All-Dielectric Self-Supporting Cables on Overhead Lines

The non-metallic optical cables strung between high voltage towers, independent of the phase conductors, are known as all-dielectric self-supporting (ADSS) cables. These cables have been widely deployed for 20 years, and have been found to provide optically reliable systems. One key limitation, however, is that the proximity of the phase conductors results in capacitively coupled currents the cables' surface. This current can be large enough (of the order of mA) so that damage can result from dry- band arcing. Traditionally the threat of damage to a cable has been defined by the system voltage. In this paper models, practical experiments and service experience are used to show that this approach is not appropriate and that it is current which truly defines the threat. In some circumstances the environment can lead to significantly higher currents than the system voltage might suggest, and so shorter life than otherwise expected may result.