Transformer bushings are porcelain and contain dielectric oil similar to mineral oil. It may be classified in to condenser and non-condenser type. The condenser type bushing consists of oil impregnated paper insulation or resin bonded paper insulation with interspersed conducting layers. This type of bushing is usually made up of equal capacitance layers between the center conductor and ground flange. These capacitance layers provide equal voltage steps, which is a uniform voltage gradient. The non-condenser type bushing consists of solid core, alternate layers of solid and liquid insulation, homogeneous insulating materials or gas filled insulation. Bushings may be further classified as having capacitance taps or power factor taps.
Transformer Evacuation System is utilized for drying out of insulation and insulating materials contained in power transformers of various sizes. This is provided with suitable condensing system for condensing water vapour & moisture and arrangement for tapping evacuated water from time to time.