medium voltage station transformer

[redlinej]

Hi guys,
Recently i clamp the ground of our station transformer (11KV-400V,60HZ,2.5MW,type-onan) and see 7.8 amp flowing to ground.I would like to know the acceptable value and if someone can guide me to the regulation for this type of transformer and voltage range.I try look but mostly low voltage regulation keep popping up ,thanks you.

 

[prc]

The grounding current(tank earthing pad to earth) depends on several factors. I don't think any acceptable limit for this current. I had seen 700A flowing to ground in a medium sized rectifier transformer.

 

[waross]

If that connection comes open while you're playing with it, You're DEAD.
There was a picture posted in one of these fora several years ago of a dead thief who tried to steal a transformer grounding cable. It is common for the transformer case to become one plate of a capacitor, particularly with a delta primary. The current is not great but it is more than enough to cause instant death followed by a small persistent arc that may remove body parts. The dead thief in the previous thread had one hand burned off. There are other factors which may cause the current to be higher than the capacitive current alone.
Sorry to be so graphic but the hidden danger of a bare cable that is assumed to be at ground potential can not be over-emphasized.

Bill
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"Why not the best?"
Jimmy Carter