A study of the behaviour of a uniaxially orientated polyethylene tape/dodecylbenzene oil insulating system subjected to electrical and thermal stresses

For high-voltage power cables the relatively high dielectric loss of paper is a disadvantage that increases in importance with increasing rated cable voltage and it becomes unacceptable at 400 kV. A uniaxially oriented polyethylene (UOPE) has been under development by Brookhaven National Laboratory (BNL) in co-operation with Battelle Columbus Laboratories since 1973 and BNL has recently constructed a 50 m length of 230 kV oil-impregnated polyethylene insulated cable with this tape (BNL (1)). The UOPE tape has a draw ratio of 5:1 and an embossed pattern on its surface to aid oil flow into butt gaps in a cable structure. A series of tests were conducted into the effect of electric stress and temperature on the tape, in particular the effect of partial discharges and the behaviour of air bubbles trapped between the tapes. The experiments were performed on layers of tape with butt gaps between adjacent tapes so that the insulation structure was similar to the insulation in a power cable