Bushings - An Overview

Bushings are insulating components which carry a conductor through a metallic component s for instance, bushings are found in Transformers as they carry the conductor from inside the transformer out to the terminals.  Bushings are usually made of ceramics.

          Bushings are also found in circuit breakers, alternators, motors and capacitors.  Some indoor substations use bushings to carry the conductors outside through the roof.  Electric locomotives also use bushings to support the overhead traction equipment.

          A bushing is usually a hollow ceramic tube through which the conductor passes.  Bushings also provide rigid support to the conductors inside.

          Bushings are used in both low voltage and high voltage applications.  In low voltage applications, the ceramic casing alone is sufficient to provide insulation to the conductor.  These bushings are known as non-condenser bushings.

           However, in high voltage application (>52 kV) the bushings are filled with insulating media such as oil, resin impregnated paper, oil impregnated paper, etc to provide greater dielectric strength.  Sulfur hexafluoride gas is also used in some high voltage bushings.   These bushings are also known as condenser bushings, as they form a capacitor between the live conductor and the equipment body which is at ground  potential