Phase-GND(N) Voltage fault (Urgent)
Phase-GND(N) Voltage fault (Urgent)
(OP)
We've got connection as following in our substation.
6/0.4kV Transformer (N is grounded) -----------BUS BAR(U/V/W/N)-------------LV Switchgear
And our system's Neutral is grounded.
In SWGR A side, all voltage measurement is OK.
But we have some problem on voltage measured from SWGR B Side.
L1 - L2 : 400V
L2 - L3 : 400V
L3 - L1 : 400V
N - L1 : 230V
N - L2 : 230V
N - L3 : 230V
GND - N : 230V
GND - L1 : 400V
GND - L2 : 0V
GND - L3 : 400V
GND(SWGR A) - GND(SWGR B) : 0V
We're in very urgent situation since P.T (that is supposed to be supply with 230V) is now supplied by 400V. (GND - L1&L3 : 400V)
If we have any damage on P.T, then our system will shutdown.
Can you give any possible reasons and what we have to try to solve this?
For now I can't understand this voltages measured.
6/0.4kV Transformer (N is grounded) -----------BUS BAR(U/V/W/N)-------------LV Switchgear
And our system's Neutral is grounded.
In SWGR A side, all voltage measurement is OK.
But we have some problem on voltage measured from SWGR B Side.
L1 - L2 : 400V
L2 - L3 : 400V
L3 - L1 : 400V
N - L1 : 230V
N - L2 : 230V
N - L3 : 230V
GND - N : 230V
GND - L1 : 400V
GND - L2 : 0V
GND - L3 : 400V
GND(SWGR A) - GND(SWGR B) : 0V
We're in very urgent situation since P.T (that is supposed to be supply with 230V) is now supplied by 400V. (GND - L1&L3 : 400V)
If we have any damage on P.T, then our system will shutdown.
Can you give any possible reasons and what we have to try to solve this?
For now I can't understand this voltages measured.






RE: Phase-GND(N) Voltage fault (Urgent)
RE: Phase-GND(N) Voltage fault (Urgent)
RE: Phase-GND(N) Voltage fault (Urgent)
I think you have created a fault on an ungrounded system but there is nothing but ground capacitance to supply ground current, which will be very little.
RE: Phase-GND(N) Voltage fault (Urgent)
RE: Phase-GND(N) Voltage fault (Urgent)
RE: Phase-GND(N) Voltage fault (Urgent)
You also think that N is not grounded, and L2 is grounded. So there is current flowing to ground from L2. Am I understanding right?
<davidbeach>
I think I need to look in to GND fault protection. But simply followings came to my mind.
1. If L2 is grounded, L2 and GND are connected and there should be big current flowing so overcurrent protection relay should operate.
Can you explain me why this doesn't happen?
We just checked Netural in transformer and it has 230V to GND(TR enclosure that is connected to
isolated grounding rodmain GND grid which isdifferent fromsame as above GND(GND of SWGR enclosure))- (Sorry for my confuse. Only Neutral in transformer is connected to isolated GND Rod.)And now we're considering to make Neutral connected to GND again(if N is not grounded for sure, We'll check this first).
RE: Phase-GND(N) Voltage fault (Urgent)
RE: Phase-GND(N) Voltage fault (Urgent)
Can you please tell me your idea?
RE: Phase-GND(N) Voltage fault (Urgent)
I suspect that you had a ground fault which blew off your system ground jumper.
Alternately
The system grounding jumper is damaged, corroded or disconnected.
Be very careful.
Someone could DIE from touching some metal part that is normally at ground potential.
If I am wrong, then nobody dies. That's good.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Phase-GND(N) Voltage fault (Urgent)
As things stand, if you connect N to GND, you will cause a short circuit because GND is connected to L2.
RE: Phase-GND(N) Voltage fault (Urgent)
RE: Phase-GND(N) Voltage fault (Urgent)
At one of the load connected to the SWGR A, L2 was connected to enclosure.
After removing this, all came back to normal. And unlike my assuming, we found Neutral line is grounded.
But still unclear since GND(SWGR A) was connected to L2, but GND(SWGR A) - GND (SWGR B) was measured 0V even though all enclosure GND are connected to main GND grid.
Anyway I'm so glad that the problem is solved.
RE: Phase-GND(N) Voltage fault (Urgent)
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Phase-GND(N) Voltage fault (Urgent)