Design and research of GIS bushing with 72.5kV environmental protection gas insulationper Title

Aiming at the 72.5 kV metal-enclosed combination electrical appliance (GIS) in which the bushing is prone to local discharge and discharge along the surface, a bushing optimization design method is proposed. Firstly, the dry air insulated GIS bushing model in the paper follows the SF6 gas insulated bushing model and carries out electric field simulation calculations on it, and the simulation results show that the electric field distribution is not uniform at the high-voltage end of the shielding cover and the outer surface of the epoxy resin and there is a high electric field in the local area, which is 20.03 kV/mm and 7.94 kV/mm, respectively, and it can not satisfy the dry air insulation. Secondly, two structural optimization schemes are proposed for the existence of high electric field: optimizing the structure of bushing high-voltage end shielding cover; proposing to add grounded shielding net inside the bushing, and analyzing the influence of the shielding net length in the range of 30-80mm on the electric field distribution of the bushing. The two optimization schemes reduce the electric field of the high-voltage end shield and the outer surface of epoxy resin to 10.60kV/mm and 4.84kV/mm respectively, and the maximum field strength of the epoxy resin casting body is lower than that of the epoxy resin with a maximum endurance strength of 30kV/mm.Finally, the optimized bushing is subjected to the frequency withstand voltage test, partial discharge test and the lightning impact investigative test, and the results of which show that the bushing meets the design requirements. The test results show that the bushing meets the design requirements.t.