A bank of 3 single phase step up transformers

[ExanD]

Hello everyone
Does anybody have experience of single phase step up transformers ?

These are some questions I have.

Can anybody answer ?

1. Is there an OLTC system inside every single pole step up transformer ?
2. If there is, how do we realize simultaneous stepping on 3 OLTC together ?
3. I am assuming there are 3 x packages for own protection sensors
(Buchhlotz, pressure sensors, hydran controller etc), am I right?
4. Are there 3 control cabinets ?
5. The windings are made of electrolytic copper?
6. Impedance voltage would be in the same usual levels as a 3-ph transformer for 220kV Uk = 10 - 14 % ?
7. How do we realize conection type (Ii0 for 3ph group Ynd)
8. Is there a photo of a similar transformer?

 

[slavag]

It's not so important, step up or step down transformers.

OLTC is operated according to Master - Follower logic, standard functionality, one phase transformer is Master, two others are Follower.

Of course every transformer is included Local transformer panel and usually one common marshaling kiosk where all identical signals ( PRD, Buchholtz, etc ) are connected in parallel ( as option ).

Three IO CT's are connected in parallel.

 

[ScottyUK]

Some designs have a common driveshaft passing through the fire walls between transformers so the OLTCs move as a gang and are driven by one mechanism.

 

[magoo2]

We've used single phase step-up and step-down transformers. The largest is 500 kVA. Most of these are used in a three phase bank to change the voltage from 34.5 kV to 12.5 kV or 13.2 kV. None of these have on-load tap changers.

If you do a search on single-phase voltage regulators, you'll see how they control voltage. They are basically single-phase autotransformers with a tap changer mechanism. They are also of very low impedance, with 0.5% or so being typical.

At 220 kV, I'm sure you are dealing with much larger ratings in the MVA range.

I'm not sure what the significance of the copper windings has to do with anything.