Automatic Voltage Regulator Devices - Parallel Operation

[mikeangel]

Hi all!

I've actually having some issues related to the theme Automatic Voltage Regulator in Power Transformers. The scenario is: a Substation with only one Power Transformer that is equiped with an OLTC and an AVR. The client (national grid company) recently have decide to construct a new bay transformer and they we've ordered a new Power Transformer also equiped in a OLTC and a AVR. The problem, is that all the the new equipment is diferent from the older (power transformer, OLTC and AVR). The AVR is from a diferent supplier/brand and my question is: with two diferent AVR devices in case of parallel operation of the Power Transformers the Automatic Voltage Regulator relays will work properly and able to perform a correct control? Should not the customer have ordered an AVR relay as it existed?

Best regards

 

[bacon4life]

There are many different methods of paralleling AVRs. Both transformers need compatible equipment, but it does not necessarily need to be the same brand on both transformers. Beckwith has several good application notes on paralleling transformers at

http://www.beckwithelectric.com/support/app-notes.html

If the original transformer was not intended to ever be paralleled, it might not have all the components needed your preferred control scheme. You might need to add components to the old bank, add cabling to both banks, or accept a larger voltage variation from using reverse reactance.

 

[RRaghunath]

Generally speaking, while preparing purchase specs for 2nd transformer that is expected to run in parallel with already existing transformer, a clause would have been included as to the requirement, providing details of the existing transformer including OLTC and AVR in the spec.
If not done this way, there could be bigger problems if the step size and range of the OLTC is different as well as if the transformer %Z or primary and secondary voltage ratings are different.
If you have confirmed the more important parameters as above and it is only the AVR you are worried, it could be a simpler problem.
1) You can check with the manufacturer about its compatibility with the existing transformer AVR for 'soft' interconnection to achieve parallel operation.
2) If confirmed not compatible, there must be a way to draw-up a hard-wired scheme with the help of the vendor design engineer.

Rompicherla Raghunath