Transformer DY11 phasing LV to HV 1

[DaDaDaDave]

Can anyone suggest a reliable way or anyway of ringing through a 6.6kV to 430v DY11 1000kVA Tx.
I want to identify the HV phase colours eg. which phase on the HV cable goes to A,B or C on the HV side of the Tx but don't want to have to melt down the HV box and cannot lift the Tx lid because of contaminated oil.
Does anyone know a device or method of connecting something to the HV cable and then from testing the LV side finding out what i want to know.

 

[jghrist]

Do a polarity test using the available HV cable ends. If the cables are connected to the HV bushings as assumed, then the polarity test will verify correct phase relationships. If not, try a different cable connection assumption.

 

[isquaredr]

Do you have an alternative known transformer which could be used to phase out the unknown transformer?
If there is no interconnection available why do you need to know? is rotation not sufficient.

 

[DaDaDaDave]

Isquaredr

There is a LV connection that i need this Tx to parallel with so you see i need to be sure that core 1 on the HV cable goes to A and the TX, core 2 on the HV cable goes to B and that Core 3 goes to C on the Tx this is what i would expect.

There would be a phasing method i could use after with the LV interconection but it would be nice if there was a method of finding out so i knew before that i was going to be right

 

[stevenal]

See

http://www.basler.com/downloads/3phXfmrs.pdf

Figure 11. Energizing H1 to H2 will enegize X1 to X0. That will likewise energize X2 and X3 to X0, but at half the voltage of X1 to X0.

 

[Marmite]

What contamination in the oil is preventing you lifting the lid? Botulism?
I can understand you wanting to know the phasing before you do the jointing, hence it might not be practicable to do as isquaredr suggests. You could join one of the HV phases to one of the LV phases and inject 430V 3 phase on the PRIMARY 6.6KV WINDING. Measure the voltages developed between the secondary 430V terminals and the primary terminals and draw a vector diagram. Don't attempt any testing like this unless you are fully conversant with what you are doing and have taken the necessary safety precautions to avoid danger.
Regards
Marmite

 

[DaDaDaDave]

Hello Marmite

The oil has PCBs in it (carsonagenic!)

Could you explain further ? Could a DC injection set be used do you think

 

[waross]

Energize primary "A" to "B" with a safe voltage. The corresponding secondary phase to neutral winding will show the appropriate secondary voltage. The other two secondary phases to neutral will show 50% of the appropriate voltage.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[burnt2x]

As marmite said! Apply 430V to either two "high side" terminals. You'll get a low voltage on the LV side approx. = 28V. The other LV terminals will read half of this or so. Be sure to discharge the terminals prior and after your tests, secure your test area, install warnings, etc.. In short, be safe.

 

[defreitas]

Exactly as burnt2x said, a simple Tuns ratio test on your TRX should solve your problem.

What we do at work is apply 1kVac on to the primary and measure the voltage on the secondary.

On a Dyn11 trx you find that applying 1kV between AB phases (HV side) you will get 37.61V only between "a" phase and neutral (LV side) and lower voltages between neutral and b &/or c.

If the same voltage is applied between BC phases, the same value (37.61V) is going to be found only between "b" phase and neutral (LV side).

Also applying the same voltage between CA phases (HV side) you will find 37.61V only between "c" phase and neutral (LV side).

Any other voltage that you find between the phases when doing the test will prove which phase is which...

Try using this excel sheet (in case you want to apply a different voltage for the test and let us know if that helps.

Good luck.

Dan de Freitas
Field Services