Electroluminescence and space charge distribution in XLPE subjected to ac fields at various frequencies

Crosslinked Polyethylene (XLPE) has been extensively used as an insulating material in underground distribution and transmission class high voltage cables. During service, diagnostic techniques are often employed to determine the operating condition of the insulation. Some techniques use frequencies much lower than the power frequency because the required high voltage power supplies are much smaller and it is assumed that very low frequencies cause less damage to the insulation. In this paper it is shown that at low frequencies more space charge per cycle remains in the insulation. Electroluminescence (EL) and the newly developed Phase-Resolved-Pulsed-EIectro-Acoustic (PR-PEA) techniques are used to determine charge injection and space charge distribution in XLPE subjected to frequencies between 1 Hz and 50 Hz.