Phasing a Tie Circuit Breaker

[SecondGen]

Keep in mind, that day the accident will happen is not tomorrow, is today if we don't take care of each other.

Well said. Safety should always be #1 priority. Everyone goes home at the end of the day.

[joaogemal]

At the end, that is what we fight for.
Thank you

[Mmfz85]

See the picture.

But, if the question was like:
You read 480 Volts on phase A and B, and Zero Volts on phase C then, the solution will be:
Roll A and B on one side of the breaker.

Attachment 31

The way you should phase at the tie cubicle is this. With appropriate meter go to A phase on both sources. You should read 0. While keeping one lead on A phase take the other lead to B Then C phase to the other source. While going to B and C phase you should read line - line voltage. The reason you read 0 is because of the phasor direction or vectors. The are both at 0 degrees.

[joaogemal]

The way you should phase at the tie cubicle is this. With appropriate meter go to A phase on both sources. You should read 0. While keeping one lead on A phase take the other lead to B Then C phase to the other source. While going to B and C phase you should read line - line voltage. The reason you read 0 is because of the phasor direction or vectors. The are both at 0 degrees.

Not really. In this situation specific is about rotation. remember that this case is not for paralleling two different sources. They are the same vectors, just coming from different places.

And, just to compliment, not only the appropriated meter, but also, and more important, PPE, live work permit and all NFPA 70E requirements for LIVE Work authorization.

[Mmfz85]

Not really. In this situation specific is about rotation. remember that this case is not for paralleling two different sources. They are the same vectors, just coming from different places.

And, just to compliment, not only the appropriated meter, but also, and more important, PPE, live work permit and all NFPA 70E requirements for LIVE Work authorization.

The angle and magnitude on either source of the same phase should be at the same degree upon the vector. That's why you read 0. Just explains why you read zero. And thanks for the safety tip.

[Mmfz85]

The angle and magnitude on either source of the same phase should be at the same degree upon the vector. That's why you read 0. Just explains why you read zero. And thanks for the safety tip.

Also you are parrelling if the tie closes. That's why you need to make sure both sources are the same vextor

[SecondGen]

Found this really good article from NETA World that covers this topic in depth. Here are some highlights related to this thread:

The only way to verify that two similar voltage systems are in phase is to determine that zero volts (or nearly zero) exists between the same phases of the two systems. A rotation (or phase sequence) meter is insufficient and unnecessary for verifying phasing. A rotation meter is useful only to check that motors will rotate in the correct direction after reconnecting leads or other parts of the power circuit.

A phase-angle meter or an oscilloscope is useful to determine if the voltages of one circuit leads or lags the voltages of another circuit, but they are not necessary. The minimum equipment required for verifying phasing is either a voltmeter or phasing sticks as necessary for the system voltage.

To understand the phasing process, it is necessary to know the voltage and phase-angle relationships that exist between the same phases of two systems (see table 1). It is assumed that the phase-to-phase voltages of the two systems are identical.



SITUATION # 2: Transformer or Tie Switch Leads Connected in Wrong Sequence
Phase-to-phase voltage is measured between the same phases of each system. The systems both have the same rotation but are 120º out of phase as indicated by the phase to-phase voltage. To correct, move the leads on one system at the transformer primary, secondary, or at the switch such that what was A is B, what was B is C, and what was C is A. If the systems are still 120º out of phase, repeat the process one more time. The use of a phase-angle meter would indicate which way to shift the leads, but that is not actually necessary.


Full article is attached. It covers some other common phasing scenarios found in the field for those who wish to read further into this subject.

[Mmfz85]

Thank you for this. As it explains what I was expressing in great detail.