COMPACT SULFUR HEXAFLUORIDE-FILLED INSULATOR BUSHING WITH REDUCED GAS-FILLED VOLUME

摘要

A high voltage gas-filled insulation bushing has an outer porcelain weather casing (10) which has a central elongated conductor (13) extending therethrough. The interior of the porcelain weather jacket is filled with sulfur hexafluoride gas. The interior of the jacket is at least partly filled with a module (15, 16) which reduces the free gas volume and can be a module formed of a wound fibrous material or a rigid or resilient dielectric gas containing foam. Either reduces the volume of free sulfur hexafluoride gas under pressure within the porcelain weather jacket and thereby reduces the potential explosion hazard if the weather jacket should be broken. The foam body can be any polymeric material blown with any suitable gas including sulfur hexafluoride or Freon. The foam is disclosed as open cell and closed cell, and in one embodiment the outer surfaces of an open cell foam are sealed with a sealant to prevent escape of the dielectric gas. The module may contain capacitance grading layers (17-22) in order to grade the dielectric stress across the outer surface of the bushing, thereby permitting a reduced size bushing for the same electrical duty. The entire bushing volume, or the free space surrounding the module, can be filled with hollow spheres loaded with a dielectric gas, or can be filled with gas-loaded molecular sieves. Processes are disclosed for using microwave energy to foam the plastic and for the manufacture of the modules.