Isolated/solidly grounded neutral ground foult phasor diagrams
Isolated/solidly grounded neutral ground foult phasor diagrams
(OP)
Hello,
Let's say we have transformer. Primary(delta or star) is connected to medium voltage, neutral is isolated. Secondary(star) connected to low voltage, neutral is solidly grounded.
What primary and secondary phasor diagrams would look like in case of 1 phase ground fault in medium voltage network?
Let's say we have transformer. Primary(delta or star) is connected to medium voltage, neutral is isolated. Secondary(star) connected to low voltage, neutral is solidly grounded.
What primary and secondary phasor diagrams would look like in case of 1 phase ground fault in medium voltage network?






RE: Isolated/solidly grounded neutral ground foult phasor diagrams
Primary: if capacitance balanced before, it will change from rotating around center of phasor triangle to rotating around one of the apexes/corners of the phasor triangle.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
In case of fault one phase voltage remains unchanged and other two phase voltage becomes equal to line voltages.
What I don't get it why no change in secondary if primary voltages have chaneged?
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
Normal operation phase voltages:
VAB=V
VAC=V
VBC=V
A phase grounded:
VAB=V/sqrt3
VAC=V/sqrt3
VBC=V
Correct me if i'm wrong.
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
The voltage that the transformer primary sees doesn't change.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
What primary and secondary phasor diagrams would look like in case of 1 phase ground fault in medium voltage network?"
From this, we get:
1. The MV side is isolated (neutral is isolated).
2. Transformer primary is connected to medium voltage.
3. 1 phase ground fault in medium voltage network.
Since there will not be any extra currents flowing in the MV network (isolated neutral and there was nothing said about capacitance, so we do not know what influence it may have), there will not be any changes in the medium voltage that the transformer primary is connected to.
There will be a change in L-GND voltages, yes. But that does not influence L-L or L-N voltages.
Sorry, I cannot be any clearer than that.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
If that were the case, the line would be shorted and the breaker would trip when there is "1 phase ground fault in medium voltage".
Don't you agree?
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
An assumption based on my perception of the usage of the terms.
For some more information on the effect or lack of effect of one line to ground connection on an otherwise ungrounded system, search this site for "Corner Grounded Delta".
Bill
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"Why not the best?"
Jimmy Carter
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
Some questions are best left unanswered. Like this one. There is nothing to question - and still, there is a discussion.
Good tip on "effect or lack of effect of one line to ground connection on an otherwise ungrounded system", Bill. Especially that "lack of effect" phrasing. That is what I said from the beginning.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Isolated/solidly grounded neutral ground foult phasor diagrams
This wouldn't happen for an ungrounded wye primary or delta as stated above.
RE: Isolated/solidly grounded neutral ground foult phasor diagrams