Partial discharge behaviour in laminated structures: effect of gaseous diffusion and penetration [turbine generators]

Studies to determine the transport mechanism of hydrogen gas in laminated dielectric materials of practical interest have been performed. Partial-discharge activity was investigated as a function of pressure reduction. The controlled variables were composition of the insulation system, ambient pressure, temperature, and molecular size of the penetrating gas. The egress times indicate that a temporary reduction in hydrogen pressure to more easily detect partial-discharge activity in a turbine generator is a feasible procedure. However, the short time lags found are in contrast to those predicted theoretically for solid slabs. They are also contrary to experience with homogeneous epoxy resins. Therefore it is probable that the predominant gas transport mechanism is effusion, due to minute cracks in the insulation, rather than molecular diffusion