Phasing a Tie Circuit Breaker

[madMAX]

Do you roll the high side or the low side or both and what phases do you roll? Or do you roll phases on both low side or high side of each transformer?

Roll A and B on one side of the breaker.

[joaogemal]

Do you roll the high side or the low side or both and what phases do you roll? Or do you roll phases on both low side or high side of each transformer?

The question didn't give much information although we can assume this is about a switchgear and, a new installation.
What this mean? It is a double-ended Switchgear and probably all the bus work is done, the transformers came in disconnected and were connected to the line side of the main breaker, In this case my best option is doing on the secondary side of the transformer.

As you can see more information is necessary to make a decision and Yes, it can be done on the primary side of the transformer. One of them, of course.

The answer is that, swap two phases, in one of the sides, which means change rotation of one side. In truth, there's a considerable suppositions for this question itself.

One side has phase sequence ABC and the other side ACB

[wild turkey]

What is the correct answer

[stuebes]

The question has an impossible scenario for two three phase 480V sources. The measurments would have to be 0V, 0V, 0V; or 0V, 480V, 480V; or 480V, 480V, 480V.

For proper phasing with a 0V, 480V, 480V scenario, simply change the two 480V phases from only one source.

Anyone doing closed transition phasing the first time should have an experienced set of eyes for guidance. No room for error here.

[Larry5443]

The question has an impossible scenario for two three phase 480V sources. The measurments would have to be 0V, 0V, 0V; or 0V, 480V, 480V; or 480V, 480V, 480V.

For proper phasing with a 0V, 480V, 480V scenario, simply change the two 480V phases from only one source.

Anyone doing closed transition phasing the first time should have an experienced set of eyes for guidance. No room for error here.

The answer is one of the transformers is bad ,second we no what we are doing so watch the negative comments .

[Larry5443]

The answer is one of the transformers is bad ,second we no what we are doing so watch the negative comments .

All phases read 120 volts across each other on a 480 volt system ,the secondary are hard bus on both sides.What is the best solution for this situation .I will let you know how we fixed it later..

[SecondGen]

The answer is one of the transformers is bad ,second we no what we are doing so watch the negative comments .

I am confused because "one of the transformers is bad" was not an option in the original question:

When phasing a tie breaker and you have 0 volts on A phase and 0 volts on B phase and 480 volts on C phase what is the right way to phase this .Do you roll the high side or the low side or both and what phases do you roll .Or do you roll phases on both low side or high side of each transformer.

[SecondGen]

Has anyone seen this question on the NETA exam? This question would get me because NETA looks for best answer, and if my two best options came down to roll the primary of one transformer and roll the secondary of one transformer I would have to say roll the primary of one transformer, because the transformer will have to be shut down anyway and it would be much easier to switch two leads inside of a primary switch than who knows how many on the secondary side of the switchgear.

If the option said roll either, that would be different story. So I would be curious to know exactly how this question is worded.

The question didn't give much information although we can assume this is about a switchgear and, a new installation.
What this mean? It is a double-ended Switchgear and probably all the bus work is done, the transformers came in disconnected and were connected to the line side of the main breaker, In this case my best option is doing on the secondary side of the transformer.

As you can see more information is necessary to make a decision and Yes, it can be done on the primary side of the transformer. One of them, of course.

The answer is that, swap two phases, in one of the sides, which means change rotation of one side. In truth, there's a considerable suppositions for this question itself.

One side has phase sequence ABC and the other side ACB

[joaogemal]

The answer for the problem, in a scenario of: 0 Volts, 480 Volts, 480 Volts is.....
- roll the two phases with the 480 Volts reading -
To make a decision where are we going to roll the two phases (?)
Yes, you have lots of options with different scenarios. That is the beauty of making decisions.

[joaogemal]

The answer is one of the transformers is bad ,second we no what we are doing so watch the negative comments .

With due respect I didn't see any negative comment. As a matter of fact and as a good professional, any safety advise should be always welcome. I like to work around people that don't loose any opportunity to remind us about safety.
Keep in mind, that day the accident will happen is not tomorrow, is today if we don't take care of each other. Team work.

And yes, the question wasn't very well formulated, there was no "transformer is bad" in the answers. Unless, of course, the intent was to misled your audience.