Foil inserts are located at fixed radial intervals, which aids in distributing and stabilising the electric field across the bushing insulation. The condenser core consists of coaxial layers of electrical grade Kraft paper and conducting foil inserts of varying lengths. In order to cope with the high electric field stresses generated at high voltage, condenser bushings are formed from an inner capacitance-graded insulated core, which is sandwiched between the central current carrying tube and external insulator. Compared to bulk type bushings, condenser bushings are relatively complex in their construction. Due to dielectric strength limitations, the use of bulk type bushings is restricted to system voltages of 72 kV and below.Īt higher system voltages, condenser bushings are used. Whilst the traditional porcelain insulator offers mechanical sturdiness and a long service life, the application of silicon rubber is becoming increasingly popular due to its lower cost, ease of handling, and its surface hydrophobicity (which reduces the risk of pollution related flashovers). The surrounding insulator may be manufactured from porcelain or composite resin silicon rubber. The below video is an extract from our Electrical Bushings Course Online Video Course.Ī bulk type bushing consists of a central conducting rod usually manufactured from copper or aluminium, which is encased by an insulator. Power Transformer Bushings Highlighted Classification and ConstructionĮlectrical bushings can be broadly divided into two major categories depending upon how they are built and assembled:Įnjoying this article? Then be sure to check out our Introduction to Electrical Bushings Video Course! The course has a quiz, handbook, and you will receive a certificate when you finish the course. Enjoy! They perform this function by providing an insulating barrier between the live conductor and the metallic (conducting) body of the electrical apparatus (which is at ground potential). These seemingly simple devices perform the critical function of carrying current at high voltage through equipment enclosures.
Electrical bushings are essential components for a wide range of electrical equipment such as power transformers, shunt reactors, circuit breakers, and capacitors.
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