Bulk Type Bushings
A bulk type bushing consists of a central conducting rod usually manufactured from copper or aluminium, which is encased by an insulator. The surrounding insulator may be manufactured from porcelain or composite resin silicon rubber.
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). Due to dielectric strength limitations, the use of bulk type bushings is restricted to system voltages of 72 kV and below.
See our main electrical bushings article for further information.
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How Electrical Bushings Work
The below video is an extract from our Mechanical and Electrical Engineering Explained Online Video Course.
Enjoying 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!
Additional Resources
https://en.wikipedia.org/wiki/Bushing_(electrical)
http://www.electricalunits.com/bushing-of-transformer
https://testguy.net/content/257-high-voltage-bushing-maintenance-techniques