Transformer core bushing

[basilasq1]

Hi everyone,

While working with a 36/25kV 25MVA power transformer, I came across something labelled as a 'core bushing terminal'. Is this a grounding connector for the transformer core? I've never came across this before.

Can someone please clarify its purpose?

Thanks

 

[ScottyUK]

It is likely to be a bushing which normally has an earth link fitted to connect the bushing to the tank. Its purpose is to allow testing of the insulation between the core and the tank.

 

[VTer]

On larger transformer I usually specify the core ground to be brought out of the transformer tank through the bushing and bonded to the tank on the outside. It allows me to remove the ground bond and check for additional inadvertent grounds.

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla

 

[prc]

Normally there will be three small bushings ( 2 or 6 kV) in a terminal box over the tank- one connected to core,second to core clamping structure and the third to tank .In service all will be shorted together. But after removing links one can check IR between core to earth,coreclamp to earth and core to coreclamp. Usually a minimum IR of 1 Megohm is expected in service. Any shorting can be an abnormality that may lead to circulating currents and overheating.