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Tracing the 3-phases of a 3-phase generator

Tracing the 3-phases of a 3-phase generator

Tracing the 3-phases of a 3-phase generator


I have a 3-phase generator connected to a power grid. The power grid supplies electrical power to many one phase systems. I know that the load should be distributed equally on the three phases of the generator. The guy that made the grid installation did not label the power lines, and now i'm stuck with an unbalanced load on the 3-phases.

Is there a way or a device that allow me to trace/detect each line in the power grid connected to which phase of the generator's 3-phases?

i can't cut of power on the grid ,so cutting off power on one phase and tracing it is not an option.

Thank you.

RE: Tracing the 3-phases of a 3-phase generator

If the load is close to the generator main bus, you can take a temporary tapping from the load and measure the voltage at the generator end. If it is 0 V same phase. If it is showing a voltage then it is one of the other phase.

RE: Tracing the 3-phases of a 3-phase generator

There are phasing sets available that allow you to compare a phase at one location against a reference phase at a remote location. Set up your reference at the generator and you can determine what phase you have at hand anywhere else in the system.

RE: Tracing the 3-phases of a 3-phase generator

Maybe you should hire an electrician.
Even if you know which phase is connected to which phase, so what.
An unbalance is a load issue, not a generator connection issue.
Use a common device known as a clamp-on Ammeter sometimes called an Amprobe.
Measure the current on the incoming feeder to each breaker panel and move loads from phase to phase until the panel is balanced. repeat at each panel.
If you must know which phase is which you can build a "Thumper".
Use any load from about 5 Amps to about 10 Amps.
Connect it to one phase or in parallel with a load. Use a timer or a helper to connect it for 5 seconds and disconnect it for 5 seconds. Repeat the 5 second on, 5 second off cycle. Use an Amprobe unstream to locate the phase conductor with the current changing up and down.
Hire an electrician.

"Why not the best?"
Jimmy Carter

RE: Tracing the 3-phases of a 3-phase generator

If you are on Generator side,then it is must for you to have synchro check before connection to Grid otherwise not only phase sequence but angle between Grid and Generator will pose problem.

RE: Tracing the 3-phases of a 3-phase generator

@krisys the load is very far from the generator there is up to 3 KM distance

@davidbeach yes this kind of device that i'm looking for do you know the name of such device?

@waross you are absolutely right. However, in order to balance the load i wanna know each load connected to which phase so I can exchange loads between phases. The idea of moving loads until is balanced does not work in my case because there is KM distances between loads. Using the "Thumper" technique could work thank you!.

@amtprot i don't haven a problem with phase sequence. i just want to know wich phase is which to balance the load.

Thank you!

RE: Tracing the 3-phases of a 3-phase generator

Is this an isolated system or is it grid-connected?

If isolated, is there only one generator? If so, what will you do if it trips?

What is the distribution voltage?

Is the load served via overhead conductor or buried cable?

If by overhead conductor, in my utility we would solve this by standing with our back to the source, then choosing a phase denoting means like top/centre/bottom, or left/centre/right, or north/centre/south, or east/centre/west, whatever. Then we would traverse the entire line from source to every load, sketching a schematic on paper and measuring and recording individual phase currents at the source and at every tap....you should have the idea by now.

One phase detector of which I am aware is the Avistar...

The "thumper" approach could be employed for buried cables where the individual phases are unmarked; presumably these terminate in a daisy-chain of metalclad switchgear, or pad-mount transformers, or something like that...and if that is the case, it would have been helpful to have said so right up front.

Remember: more information yields better answers.


"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Tracing the 3-phases of a 3-phase generator

It is an isolated system

There is two generators one work as a backup

Distribution voltage is 220V

the load is served via overhead cables.

The system grid is already installed and there is no schematics.

RE: Tracing the 3-phases of a 3-phase generator

I would "train" a helper to close and open a switch every 2 seconds and switch about a 5 Amp or 10 Amp load on and off.
You will be able to identify this phase at the generator and then label it. For a one time job, keep the cost and complexity down.

"Why not the best?"
Jimmy Carter

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