The generator voltage sequence is Vab, Vbc, Vca and their vector sum equals zero. But in your calculation Vac instead of Vca used. So perhaps reverse connection in one phase may also be a reason...
Voltage Unbalance Reason
- Thread starter mrmuneeb
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One solution to the part of the riddle is the generator is ungrounded and so phase to neutral voltage may be anything, around 590V in the OP case. Another is if the actual voltage readings of the OP are taken, I think their vector sum may not be zero and so there may be a break in windings or one phase winding may be reverse connected and that is my stand.
ggunn
PE (Electrical), NABCEP certified
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- Austin, TX, USA
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No. Phase and neutral voltage to ground readings are meaningless.
ATSman
ATSman
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- San Francisco Bay Area
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- Electrical Engineer/ Electrical Testing & Controls
The reason you can't make any sense of it is because the readings are meaningless on an ungrounded wye as others have stated over and over! :roll:
you will get a reading thru capacative couple, because he DID get reading
regardless, ph-n will not be 3x ph-ph
kingpb
Senior Member
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- SE USA as far as you can go
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- Engineer, Registered
The OP has left the discussion; so in other words it's all speculation after post #5.
we know a few things
only occuring on 1 bus
VLL = 150-300 (2 @ 150, 1 @ 300), VLN = 600, VLN ~ 2-4 x VLL
we know what the ph ang must be to result in these magnitudes
it is not cool for an op to make a post asking a question about an issue (especially an implausible one like this) and not providing feedback
only occuring on 1 bus
VLL = 150-300 (2 @ 150, 1 @ 300), VLN = 600, VLN ~ 2-4 x VLL
we know what the ph ang must be to result in these magnitudes
it is not cool for an op to make a post asking a question about an issue (especially an implausible one like this) and not providing feedback
JFletcher
Senior Member
- Location
- Williamsburg, VA
That's been my main gripe with people posting questions on this form since its inception. People post the weirdest things, everyone brainstorms possible problems and solutions, and the o p rarely gets back to post what the problem was and how or if it was solved. C'est la vie...
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
mrmuneeb
Member
- Location
- Saudi Arabia
greetings to all,
the system remains normal and is running normal since 7 years, this happens always whenever there is some ground fault in the distribution, as soon as ground fault is removed by the client, these high voltages vanishes,
further more, this problem appears on generators which are in OFF condition, we found these high voltages on the primary side of transformer, (generators feeding primary side at 480V(delta), we are taking bus voltage sensing for generators also from there i.e. primary side)
for now we have to start the required engines, sync them together & then we switch on the main Ring unit that is feeding the client. we are the only source of power for that system,
whatever the engine we are running, keeps running good, as soon as it trips due to any safety sensor, boom......there goes the engine controller having high voltages appearing at the bus input burning it out.
we have grounded neutral as of now but from low voltage side only....
i was off grid on that project since last week, just returned yesterday and i really am amazed for such a huge discussion on my problem, really very grateful, i hope you all could help me out with that.
thanks again folks,......do ask if you need further clarification....
the system remains normal and is running normal since 7 years, this happens always whenever there is some ground fault in the distribution, as soon as ground fault is removed by the client, these high voltages vanishes,
further more, this problem appears on generators which are in OFF condition, we found these high voltages on the primary side of transformer, (generators feeding primary side at 480V(delta), we are taking bus voltage sensing for generators also from there i.e. primary side)
for now we have to start the required engines, sync them together & then we switch on the main Ring unit that is feeding the client. we are the only source of power for that system,
whatever the engine we are running, keeps running good, as soon as it trips due to any safety sensor, boom......there goes the engine controller having high voltages appearing at the bus input burning it out.
we have grounded neutral as of now but from low voltage side only....
i was off grid on that project since last week, just returned yesterday and i really am amazed for such a huge discussion on my problem, really very grateful, i hope you all could help me out with that.
thanks again folks,......do ask if you need further clarification....
mrmuneeb
Member
- Location
- Saudi Arabia
please see the pictures on one of the controller,
mrmuneeb
Member
- Location
- Saudi Arabia
Sir,
i really am grateful for the discussion, i was off grid as i went on that project for inspection, all i did there is grounding of all the low voltage side neutrals,
i grounded one medium voltage neutral also(solidly) but as soon as i switched on that transformer, all system went black out with the below alarm on the main ring unit that is feeding power to the client;
I>> BE , Blue & Earth(Short Circuit)
Red (I): 78 Amps (Normal)
Yellow(I): 60 Amps (Normal)
Blue(I): 894 Amps (Fault)
Neutral/Earth(I): 882 Amps (Fault)
Tripping Time : 0.02 Sec.
There is a ground fault in Blue phase and when you grounded the neutral also, you created a short circuit. Trace the ground in MV B phase and rectify.
With primary low voltage side grounded, your high voltage problem is solved. You may consider installing ground fault detector on the MV side if you want to keep it ungrounded for higher reliability.
mrmuneeb
Member
- Location
- Saudi Arabia
mrmuneeb
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