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Outdoor Transformer location

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dontexplode

Electrical
Jan 15, 2014
9
I am specifying/installing (4) 3MVA transformers that are to be located outside in the US in a hot/tropical climate (HI). It needs to be as close to the building as allowable and each other. I am looking for a guideline/standard on placing outdoor transformers. The NEC only mentions providing adequate ventillation for transformers.
I found this in IEEE C57.12.01 - 4.1.2 Temperature

The temperature of the cooling air (ambient temperature) shall not exceed 40 ºC, and the average
temperature of the cooling air for any 24-hour period shall not exceed 30 ºC.
The minimum ambient temperature shall not be lower than –30 ºC.

Does anybody know of any other standards or guidelines for installing these?
The team wants to place them right by the building and next to each other and need some help figuring this out.

Thanks.
 
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Check with the local authorities (utility, wiring inspector, fire dept., etc.) They may have some specific requirements in addition to the NEC & NESC safety requirements. Also check with the property's insurance carrier, as they my have issue with so much oil filled equipment next to the building in the event of a transformer fire or building fire.
 
If the transformer if filled with mineral oil see: NFPA 850 ch.5[5.2.4].
 
Points to consider:

Four transformers placed line-of sight and fairly close to each other: should one of the centre units fail explosively it could well take out the transformers on either side of it as well...

Unless the entire facility is taken out of service and off potential at once for simultaneous maintenance on all transformers, adequate clearance will have to be provided to comply with the limits of approach to energized equipment such that work can be safely performed on one bank at a time. This will additionally provide adequate room for air to circulate around the units' cooling facilities.

Because of the foregoing it might be wise to place a rigid non-conductive flameproof barrier between each unit and its neighbour. Such a barrier can also provide worker safety by virtually eliminating any risk of electrical contact with live components while maintenace is being performed.

As noted above, it may become necessary to increase the fire resistance rating of the building's wall adjacent to the transformers.
 
I am in the southern hemisphere. We avoid north facing transformer bays as this will put the transformer in the sun for most of the day. I think your ones should not face south. We sperate with "Blast walls." Thick concrete walls casr with re-inforceing. Each transformer bay has a well capacity to hold all the oil within the transformer plus 10%. In the old days we used to fill the bays with granite chips. There is a space factor calcualtion for this if it is used. If the oil escapes and catches fire, the chips allow a wicking action to prevent an all out flame. Older units have slatted wooden doors but these rooms tend to make them run hot so we use gates with diamond mesh fence. The poles and gates have to be earthed. Installation rails are sometimes fitted for larger units when they cannot be dropped into position by crane and have to be pushed in. We have wheels fitted and have jacking pads for final positioning. We have a requirement to Prohibition notices and warnings along with resusitation instructions and instructions on what to do in case of a fire. We have an earthing bar at the rear where all the earths are connected. There is a link that connects the earth to the earth mat conductors. The link is removed when the earth mat is required to be tested. I am trying to motivate to get the lighting put onto motion sensors as if they come on with light sensors, the insect infestation is a problem and where there are insects there are spiders and rats. Then the snakes come to eat the rats. Not technical but I hope this assists.
 
As mentioned by 7anoter4, the main issues will be covered by the applicable fire codes. The clearance to the building will depend on the wall construction and other issues such as overhanging rooflines, etc.

Once you get the spacing from the building, then you will want to allow similar apacing between each unit. This will also depend on the type of transformer. Are these pad-mounted or substation type? If substation type - just self-cooled, or with fans?

Assuming these are oil-filled, if reliability is of high concern, some type of fire barrier between the units may be desirable - it won't be an NEC requirement. The insurance underwriters often have their own requirements and guidelines that can be more restrictive than the NEC.

I don't think the -30 C will be a problem in HI.
 
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