Lightning Impulse Ageing of Hdpe

This work is concerned with the hypothesis that lightning impulses can lead to accelerated ageing of extruded polymeric cables. The behaviour of an insulation material when suffering lightning impulses is different from that for DC or power frequency over-voltages. Shaped HDPE material samples have been manufactured using a mould tool. The samples then may be electrically aged using one of the Tony Davies High Voltage Laboratory's impulse generators. A realtime software based monitoring tool has been designed to control the impulse wave-shape and process the measurement data. Sets of identical lightning impulses were applied to samples and this was then followed by ramped AC breakdown tests. The obtained results were analyzed using the Weibull distribution method to identify the difference in lifetime. These results will inform the further development of models describing the multifactor ageing mechanisms that inservice cables experience.