Long-term stability of oil impregnated polypropylene laminated paper insulation under high electrical stress

UHV cables such as 750 KV and 1000 KV cables will be designed at high electrical working stresses because the insulation thickness is restricted by dimensional limitations due to manufacturing, transportation and installation conditions. Therefore the insulation material for UHV cables must have high electrical strength, low dielectric loss and stable dielectric properties under high electrical stress. Polypropylene laminated paper has high electrical strength and low dielectric loss but to insure the stability of dielectric properties under high electrical stress was the remaining problem. This paper describes the results of a long-term stability test of oil impregnated polypropylene laminated paper insulation under high electrical stress. The results showed that high electrical stress of up to 40 KV/mm did not damage the properties of this material and indicated that it is a promissing insulation material for UHV cable.