Air Condition in Oil Transformer Room

See IEC 60354.

Basically,the outlet exhaust temperature should never exceed 40 Degrees at full load,if the transformer is designed for 40 degrees ambient.

Ambient-temperature correction is given in 2.7.6.

Otherwise,de-rating of the transformer is required to prevent premature failure.

That's a pretty wimpy transformer, you mean 40C rise over ambient...

Of course,grasshopper!

That is how transformers are rated.

Lower rise is a higher efficiency transformer than a higher temperature rise.

One needs to bear in mind that:

• ventilation provides cooling, and
• air conditioning provides comfort.

Differential temperature provides heat transfer:cooling.

Air conditioning provides moisture reduction as well as cooling,and the circulation of the cooler air around and through the transformer enclosure provides a greater temperature differential,and more cooling of the transformer occurs.

Semantics aside,the exiting air from the enclosure should never exceed the temperature rating of the transformer,generally taken as 40 degrees.

Designs may vary,so follow the specs of the transformer.

Well, that's valuable advice for the Original Poster, who may well be able to adapt it to local circumstances.

With most insulation systems reduction in temperature significantly increases life expectancy.

In electrical drive rooms in the paper industry I have seen the rooms cooled with AC to 15 to 20C, and the electronic equipment and transformers have lasted over 30 years.

The advantage of the AC has also been a significant reduction in humidity, that otherwise runs over 90% saturation. Corrosion slows down significantly with cooler temperatures and the humidity on the dryer side.

Transformer Oil can function well right down to -10 degC (The pour point is still lower for Naphthenic oils) . The Air conditioned room temperature setting generally is about 25degC.

Hence, there shouldn't be any issue with transformer oil effectiveness.

I am guessing that the oil may not be mineral based but Silicone based (from fire safety point of view). This is better than mineral oil from pour point as well as from flash/fire point. Further, the oil cannot sustain fire without external source.

Oil filled transformers in larger sizes have de-hydrating breathers to keep the oil dry.

I do not think it is standard on small sizes.

Air conditioning removing humidity would help keep oil dry, assuming the transfo breaths the air in the room.

I would wonder what happens if the air conditioning fails - will everything overheat because there are no air entries & exits to open?

Losing the AC in the paper mill drive room usually occurs on the hottest day of the year (LOL). The room temp and AC unit is alarmed. There is a mad scramble to open doors and put up huge portable fans to get the heat out.

Then the witch hunt begins - when was the last maintenance done? Why did the PM not prevent it, etc.

Truth.

The short answer is that it is usually not economical to refrigerate a power transformer, but air conditioners are used all the time for associated close coupled equipment to provide dirt & dust isolation, and cooling for other electrical equipment.

Providing your air conditioner does not chill the air below the dew point in the room, including warm air leaks from outside, creating a conductive water layer, you will be fine. The air conditioner installation must not compromise the fire rating of the vault, or room the transformer is in, depending upon where you are, and fire prevention measures..

Dear all

Many thanks for your answers