1, 40kV and below pure porcelain insulating sleeving. This kind of casing has two kinds of structure, which are guide rod type and cable wearing type. The guide rod is used for the low voltage casing of the transformer, and the cable type is used for the 10~20kV high voltage outgoing line.
2, 40kV and the following large current casing. The casing has two kinds of structure, guide rod type and capacitive type. The guide rod type pure porcelain bushing is used for the low voltage winding outlet of the medium capacity generator transformer, and the capacitance bushing is used for the outlet winding of the low voltage winding of the large generator transformer.
3, 66kV and above oil paper capacitor bushing. The inner insulation of the casing is a capacitive core that is coiled alternately with the insulating paper and aluminum foil. The capacitor core and the porcelain sleeve are filled with insulating oil. The connection of the casing and the winding has two structures: guide rod type and cable wearing type. The oil paper capacitor core is alternately rolled over the conductive tube by 0.08~0.12mm thick cable paper and 0.01mm thick aluminum foil.
4, 66kV and above the adhesive paper capacitor bushing. The inner insulation of the casing is a capacitive core, which is made of adhesive paper and aluminum foil alternately. The capacitor core and the porcelain sleeve are filled with insulating oil, and the lower part of the sleeve does not require a porcelain sleeve. However, the tan delta of this casing is large, the adhesive paper is easy to crack and produces partial discharge, which has stopped production at present.
5, Resin cast capacitor bushing. The main insulation of this kind of casing is also a capacitive core made of insulating paper and aluminum foil alternately, and the epoxy resin is poured out to become a solid insulation casing. The casing can be used as an oil – gas casing, the upper part is embedded in the GIS pipe, and the SF6 gas is filled in between them; the lower is immersed in the transformer oil.