The Influence of Water on the Electric Strength of an Ethylene-Propylene Insulation

Needle tests on samples of ethylene propylene copolymer based insulation after water absorption have confirmed that the short term life at voltage is extended by the presence of water. Also it is shown that water is desorbed more rapidly than absorbed and this is accompanied by a reduction in electric strength. This result implies that tests on cables after water immersion should involve a short drying period to ensure that any deterioration is detected.