Omicron CP TD1 - 7 Capacitance and DF Measurement on High-Voltage Bushings; Introduction; Types of Bushings

Capacitance and DF Measurement on High-Voltage Bushings
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7 Capacitance and DF Measurement on
High-Voltage Bushings
7.1 Introduction
High-voltage bushings are essential parts of power transformers, circuit
breakers and of other power apparatus. More than 10% of all transformer
failures are caused by defective bushings [4.2]. Although the price for a bushing
is low compared to the costs of a complete transformer, a bushing failure can
damage a transformer completely. A regular capacitance and DF measurement
is highly recommended.
7.2 Types of Bushings
Figure 7-1 Principle of bushings
Wall,tank
Main insulation:
• Solid
Ceramic, cast insulation,
synthetic resin bonded paper,
resin impregnated paper,
composite
• Liquid: oil
•Gas
Ambient:
•Air
indoor
outdoor
•Oil
•Gas
Conductor
Flange