open delta connection 1

[pichu1970]

hi
we have open delta connection for earth fault (drawings attach )
there is a way to no in which phase i have the ground fault before i check with megger?
i mean after i disconnect to 2 transformer and i have just the bus bar

 

[sushilksk]

I think it should be "KNOW" in place of "NO", and the answer is "NO".

 

[waross]

Yes there is.
See here:
thread248-477214

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

 

[RRaghunath]

Broken delta voltage measurement principle is used to detect earth faults in unearthed or high resistance earthed systems. In such a case, the protection gives alarm and the operator is supposed to plan checking which feeder is faulty by switching-off the outgoing feeders from the busbar, one by one.
There is no way to find from the relay itself the faulty feeder.

 

[waross]

Electricians have been identifying the grounded phase for about 100 years by checking which PT has zero Volts.
Been there, done that.
About 50+ years ago, I worked in an old plant with ungrounded delta power and ungrounded single phase control circuits.
Looking at a voltage across the broken delta tells you that there is a ground fault.
Then looking at the voltages across the individual PTs tells you which phase is grounded.
I am assuming that the budget does not allow the purchase of the good quality relay suggested by David.
Many of us have worked under that constraint as well.

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

 

[cranky108]

If the budget does not allow the purchase of a good quality relay, then one should ask, what is this business here to do, and what are there real values?

Yes I understand small business can't afford everything, but I have also seen utility companies that question the purchase of a secondary relay, because they want to keep rates low.
I am a little sensitive to budgets comments, and wonder about the real concerns behind them.

 

[itsmoked]

and what are [!]their[/!] real values?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Going back to the original question:

there is a way to no in which phase i have the ground fault before I check with megger?

From a trouble shooting perspective, rather than the design of a new system, the grounded phase may not be determined from the simple relay across the open delta.
The grounded phase may be identified before the power is disconnected by a simple voltage test across each individual broken delta transformer secondary.
If this is an existing installation it is unlikely that management will agree to the purchase of an expensive relay.
Installing three ground detector lights is something that is cheap and easy, often with spare parts on hand, and that may be done "under the radar" without management being aware of the details.

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

 

[cranky108]

If you have another phase reference, you can tell which phase is grounded from the broken delta. That is the phase that is on the open delta will be 180 degrees from the faulted phase.