Unbalanced voltage

[Emiljani]

Hello !

I am an electrical engineer working in a cement factory.
We have a power plant installation of 3 x 8 MW.
I am facing a problem with the unbalanced voltage.
We are using PT's for measuring voltage (6 / 0.1 KV).
This PT have two secondary windings. First one is wye connection and there is the other one which is an open delta connection for measuring neutral to earth voltage.
This second one when we are running the biggest MV motors is going up to 9.5 V. I want to know how can i find the reasons of this unbalance and how can i fix that.

 

[waross]

Have you checked your motor for unbalanced resistances or impedances to ground?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[alehman]

Open delta can't be used to measure neutral voltage. How are you measuring 9.5V?

 

[waross]

Hi alehman;
See Marmite's post in:
Comparison of zig zag and open delta transformers
thread238-222776
Apparently IEC defines what we know as a broken delta as an open delta. This may be an IEC poster.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[alehman]

Ah, so. Maybe the OP can clarify.