The gassing properties of low-viscosity cable oils

Although the gassing of electrical oils under stress has been studied for many years and discussed by a number of authors (1-4, 6-8, 10,11), there appears to be no general agreement as to test methods nor even as to the influence of some of the major test variables. Recent work of Basseches and co-workers indicates that various free-radical reagents will greatly reduce the gassing of paraffinic oils when tested at sub-atmospheric pressures (1,2). Although no gas is evolved in their test at atmospheric pressure, these additives are known to lengthen the life of oil-impregnated capacitors (9). The question therefore arises as to whether the free radical reagents have any beneficial effect in cable oils. In the work reported here, we have investigated this and related questions regarding the mechanism of gas evolution from oils.