Effects of Lightning Impulses on the Dielectric Properties of Hdpe

Impulse over-voltages are very common phenomena in electric power systems. Switching impulses are created by switching surges or local faults while lightning impulses are due to lightning strikes to overhead lines. Both impulses can travel as waves in the system, damaging insulation components and equipment. This paper shows that there may well be a reduction in electric field strength of the insulation of a power cable that experiences a lot of lightning impulse overvoltages. The paper also provides insight into the dominant ageing processes through the analysis of dielectric spectroscopy measurement data.