Transformer Core and Clamp Grouded

[Heinz69]

As far as I know, the bottom part of the transformer clamp is not grounded. However, the upper transformer clamp is grounded at one point. Basically, the transformer core and clamp are grounded at one point, although there is an insulation material between them.

What's the implication if the bottom clamp touching the core? Let's say due to insulation failure between clamp and core?

Why is only the upper part of the clamp grounded?

 

[prc]

Normally upper core clamp is connected to lower clamp through the metal tie-plate on the core front.Depending on the rating of transformer circulating currents may flow with double earthing.

 

[stevenal]

This is known as a core ground fault. It will cause arcing at the touch point that will show up in gas in oil analysis. I've seen resistors put in the core ground lead to prevent the circulating current and arcing. The core top is a more convenient location to ground if maintenance is needed.