The insulation properties of dielectric coating in gases

The power equipment such as gas insulated switchgear (GIS), gas circuit breaker and gas insulated line use SF₆ gas for insulation medium. However, SF₆ gas insulation system is required for a further downsizing of the equipment while keeping a high reliability for saving the cost or reducing SF₆ gas usage, one of potent green-house gases. This paper deals with the breakdown characteristics of epoxy dielectric coating with thin thickness (<; 1mm) in SF₆ gas and dry air. The experiments were performed with lightning impulse voltage using the test chamber applied some part of GIS. Both SF₆ gas and dry air were applied to the gas pressure at 0.3~0.5 MPa. The epoxy powders with different thickness were used as coating material on the inner shield. The effect of dielectric coating was evaluated by first breakdown voltage each coating thickness. In addition, we investigated the effect of dielectric coating by thermal stress.