Large Dry Type transformer nameplate information about tap settings questions.

[bdn2004]

See the attached photo of a large dry type 12470 - 4160Y/2400V transformer.

Questions:

1. What does type HT mean?
2. The tap settings...why is that the low voltage - 4160V, doesn't change with the various tap settings?
3. The diagram doesn't show a connection to the ground. Is this common? I've not seen this installation, is it typically at this voltage D-Y, not grounded?

Thanks, for any discussion....

 

[stevenal]

1. A GE designation
2. These are rated voltages, and the rating on the low side doesn't change with high side tap selection.
3. User choice.

 

[bdn2004]

So what you are saying is...get the right actual voltage on the high side taps and you'll get 4160V out. This study we're looking at says the voltage is 4250V on the secondary side. We're trying to get the more accurate with the actual field installation. The question is..is this an error or were the taps set up on purpose to cause a higher secondary voltage to allow for voltage drop?

 

[ScottyUK]

Put the stated voltage onto the HV terminals and you'll get 4160V out at rated load conditions - it will rise a bit off-load.

 

[stevenal]

Yes, 4250 looks pretty close to what you would see if the primary was 12470 and the taps set to 3-7.

Scotty,

I believe this may be an ANSI/IEC difference. In my (ANSI) experience using the nameplate voltages will get you close to the ratio determined with a ratio test performed without load.

 

[bdn2004]

Thanks for the follow up. That 4250v looks like metered data to me...if you were doing this power study would you change it or is the nominal voltage the value to use?

 

[stevenal]

I would use actual metered data when available.