Transformer Location

[power2020]

Our project is inovoved with lot of ONAN type transformers (11kv/400V). All of our transformers are going to be placed in a row with fire barrier/brick wall, with concrete covered roof, with front side two double gates with mess fences.
The issue is whether these transformers can be indoor mounted with complete covered roof (and with proper oil catchment area).
Can the transformer roof be with Structural roof for ONAN type?
Does any standard say about ONAN transformer roof details? whether it is required or not required as a sfatey point of view? what does NFPA say?

Any info.. greatly appreiciated.

Thanks..

 

[Marmite]

The basic answer is yes, the transformers can be enclosed. They will probably last longer and need less maintenance if protected from the elements. You don't mention the ratings of the units. The issue is whether the enclosure has enough ventilation to remove the heat generated by the transformer. The method of cooling the transformer has no bearing on the structure of the roof per se. Transformers upto say 2MVA are routinely enclosed. Larger transformers may be enclosed but with the radiators mounted externally with oil pipes passing through the wall. I presume yours are in the former category being 11kV/400V, and are cable connected, not open bushing. Providing you can get the transformers in and out from the front, you can build a structural roof.
Regards
Marmite

 

[power2020]

Thanks Marmite,
our transformers are 3MVA and 1.6MVA range and all are ONAN type.
The trnaformer room height is around 4meters, with structural roof.

 

[tinfoil]

Its not how big the space is, its whether or not you are ensuring that the transformer(s) can stay cool enough while running.

ALL transformers, regardless of size, produce heat, with the amount of waste heat increasing with the load it is carrying.

You must ensure enough ventilation to remove this heat, or risk damaging your transformer.

A thermostatically controlled forced-air vent system MAY be enough, if you are not in a hot climate where this may prove inadequate.

(A 99% efficient 3MVA xmfr is going to produce ~30kW of heat at full load. This is about the same as 20 baseboard heaters in your home!)

 

[AusLee]

You should consult a mechanical engineer and provide him with the following data:

1. heat dissipation of each type of trafo.
2. how many trafos are likely to be operating at the same time.
3. what is the required internal temperature.

He will use the ASHRAE tables to find the average maximum temparature in the zone of installation and calculate how much air circulation is needed (cfm or m^3/hr).

Since it is hardly likely that any AC will be provided, the mechanical engineer might request more louvered openings in the walls.

You should also communicate the data to the structural engineer, as excessive heat might evaporate the water from the concrete used in the construction of the separations walls, and hence an appropriate concrete mix must be used, etc.

 

[power2020]

Thanks Guys,
unfortunately, i dont have a mechanical engineer to calculate this requirement.
However, each of my tranformer is enclosed in 6mx5.2m area with height of 4m meters and it is enclosed 3 sides only ane side is with full opening / double gates.


Do we require a forced ventilation (FOR 3MVA, 0NAN, 11/3.3KV). or any natural venitaltion window are sufficient?

Thanks tinfoil for your info,

 

[power2020]

What are the advantages of a transformer like 3MvA located in structural roof of 4 meters height. since this transfomrers, ONAN type, anyway rated for outdoor duty, how does the roof will help?

Thanks