Out of Phase voltages?
Out of Phase voltages?
(OP)
This question is mainly in regards to consequences. I have a station service throw-over scheme to put in service; and I'm wondering what happens if it's connected wrong. I'm talking phase A station service tx on the normal and accidentally using phase C station service tx on the emergency. What's the worst consequences assuming no sync check relay and no time delay?






RE: Out of Phase voltages?
RE: Out of Phase voltages?
RE: Out of Phase voltages?
RE: Out of Phase voltages?
RE: Out of Phase voltages?
If the transfer is open (first source disconnected before second source is connected) the currents will be less but still very damaging, especially if any motors are running. The out of phase transfer essentially tries to jerk the motors ahead or behind 120 electrical degrees instantaneously, possibly causing considerable mechanical damage to the motor, the couplings, the load and the foundations.
RE: Out of Phase voltages?
RE: Out of Phase voltages?
You MUST check phasing of regular and emergency sources!!!
First issue is explained above. It's SC on the bus in case of paralleling of two sources. Or stress on the motors in case of fast transfer.
Second issue, if your emergency in out-of-phase , your motors will run in reverse rotation.
Best Regards.
Slava
RE: Out of Phase voltages?
RE: Out of Phase voltages?
Now look at it this way cbradley, I am not aware of what kind of scheme you have at your distribution substation, but consider the following scenario:
If you look at a basic two transformer substation feeding two separate buses and a normally open bus tie CB between them. You will typically not find a synch check relay involved in the closing circuit of this bus tie breaker, at least from my experience and the utility I use to work for. Now, if you think of one station service transformer (normal) being fed from one bus and the other station service transformer (emergency) being fed from the other bus why would the secondary's of these transformers need a synch check relay if the HV primary bus tie breaker closing circuit does not?
My comments are only based on assumptions of the configuration of your distribution substation. There could be factors that I am not aware of that would could lead to unforeseen issues that would require a more thorough throw-over scheme.
RE: Out of Phase voltages?
And what with your customers????
After repair of cabels, second thing is phasing.
Sorry, I don't agree.
RE: Out of Phase voltages?
Not sure if I am following your concerns correctly. I think that ultimately it would require a better overview of this situation (schematics) to come to a clear understanding of this situation.
clos
RE: Out of Phase voltages?
RE: Out of Phase voltages?
RE: Out of Phase voltages?
Note that I said usually. Always exceptions.
The scenario clos proposed is actually a good argument against a closed transition. If transformer #1 trips taking out the primary station service initiating a closed transition to the other service, during the closed part of the transition both services will be overloaded as they try to pick up the bus 1 load. If current is high enough, or closure is long enough, both fuses will blow leaving no station service.
RE: Out of Phase voltages?
I'm not right, I re-read all posts again .
Sorry, my bad. Some blackout.
Clos , I don't understand you .
Best Regards.
Slava
RE: Out of Phase voltages?
In this case I agree with Slav and dpc and all that described a catastrophic failure
RE: Out of Phase voltages?
See more from ATS manfacturer, GE Zenith who provides "out of phase" transfer sensing.
RE: Out of Phase voltages?
RE: Out of Phase voltages?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Out of Phase voltages?
What if the phase rotation was correct and when closing the same phases were closed together however they were slightly out of phase due to different circuit paramaters on each network.
In other words, instead of closing in phases A to C (Big Bang!) we closed in both A phases (A to A) however these A phases were out of phase by some amount due to paramaters (Network Reactances) on their two respective networks. Would we still have a big bang?
RE: Out of Phase voltages?
RE: Out of Phase voltages?
The synchroscope was 30 degrees out. This was generators in the same plant and real power,not a reactive phase shift. Most times the installation would survive closing at 30 degrees of displacement. Once or twice a month, when the boys closed a little early and at a greater angle, a breaker would trip.
Once or twice a year they would come in a lot early and blow a coupling.
This was real power and the generator would have to make an abrupt angular shift to line the poles up with the rotating field. The equipment would survive closing at 30 degrees of displacement.
Your question is a little different. If the phase displacement is the result of reactive voltages, that implies that the lines are at differing power factors.
Closing on this would result in enough reactive current flowing through the breaker to give a weighted average to the power factor. Probably no big deal.
HOWEVER
If your 30 degree displacement is the result of an odd number of delta/wye conversions, it becomes more serious. Close in expect heavy currents possibly in excess of full load current. With a lot of miles of line expect a lot of energy to be lost heating transmission lines.
By the way, I agree completely with davidbeach. His system is many times larger than mine and not as forgiving as the small generators.
Bill
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