IS THERE A MULTIPLE MVA RATING FOR TRANSFOMER WITH OIL DIRECTED WATER FORCED COOLING (ODWF)? 2

[subash148]

Hello,

I am familiar with Transformer MVA rating being increased based on the type of cooling. For instance, Transformer with ONAF type cooling, will have two MVA ratings. One rating for the oil natural cooling by convection and other higher rating with air forced type cooling using fans.

Does any body familar with Oil Driven Water Forced (ODWF) type cooling? Does transformers with this type (ODWF)of cooling also has multiple rating?

Regards,
Subash

 

[cranky108]

Maybe, but so few of use have seen one of those. The manufacturer nameplate is the best place to look.

 

[prc]

ODWF transformers do not have any multiple ratings.Of course there will be stipulations that even with the loss of pump or loss of cooling water,hot spot temperature shall not exceed 120C within 30 minutes etc.

 

[mgtrp]

This type of transformer cooling method is very common at hydro power stations in New Zealand.

There is no "oil natural" rating with ODWF transformers because the oil pump and cooling water should always be running while the transformer is in service.

 

[crshears]

Hello Subash,

These types of transformers are very commonly used in hydro-electric power generating stations world wide.

The last part of mgtrp's post above is correct - - the only modifier would be in very cold weather; see my anecdote in the thread at

http://www.eng-tips.com/viewthread.cfm?qid=358868

Hope this helps, although it might not, since there may after all never be any "very cold weather" where you are...

CR

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

 

[prc]

Today watere cooled power transformers are used not only at hydro-electric power stations, but also at the following locations
1) At aluminum smelters, arc furnace steel mills etc. Here OFAF coolers will not be effective due to heay dust deposit on cooler tubes.
2) At urban areas, for underground substations.
Even at hydro power stations if space is available OFAF coolers are used to reduce maintenance issues. But for underground power stations there is no other alternative.