Switchgear and Transformer Clearances/Location

[sonic02]

Hi All,

First question:

We have a new 500kVA, 13.8kV/600V dry-type ventilated transformer to be installed in a new electrical room. The dimensions of the electrical room is sufficient so real estate is not a concern here. My main concern would be the most ideal location of the transformer; either against the wall with about 1ft clearance for ventilation purposes or about 3-4 ft away from the wall. I would prefer the first option, but that might not be the best from a maintenance point of view as well as cable terminations for a transformer of this size. Any thoughts/comments?

Second question:

Facing the 500kVA transformer is a new 15kV MV Metal-Enclosed Switchgear. My questions here is the clearance required between these two equipments. Table 56 of CEC 2006 states that 1.9m is needed as a minimum working space for that voltage class. Do I need to apply that minimum clearance for my application here? Or would just 1m, as stated 2-308 CEC 2006, suffice as clearance between the two equipments. It’s less than a meter difference (i.e. 1.9m vs 1m) here but it is the concept that I would like to understand.

As this is a new installation, I’m free to move around to ensure clearances and egress are met.

Appreciate any comments/thoughts?

Regards,

Sonic

 

[cranky108]

Question: If the transformer were to catch fire, how much damage would it cause to the wall?

Question: Do you need to go between the transformer and the switchgear for maintenance, and is it an arc-flash concern?

Question: If there was a fire in the room, how much space do you need between the equipment?

Not that I know the answers, I just believe these are good questions which might lead to your answers.

 

[sonic02]

Hi cranky,

Your points noted. Any other thoughts/comments anyone?

 

[7anoter4]

If the transformer room is destined for this transformer only and the wall are concrete or bricks made 1 ft is enough for
ventilation purpose. The 13.8 kV side shall be against the wall and a kind of barrier should be provided in front of low voltage side.
Another solution it is a Metal clad substation where the transformer could be supplied complete with an integral IP31 sheet steel enclosure, with termination boxes and switchgear if required. See IEEE Redbook "Unit Substations"ch.10.5. See -for instance:

http://www.estv.ipv.pt/PaginasPesso...eratura complementar/Trans_Range_Brochure.pdf

A fire resistance wall could be provided between transformer without enclosure and a switchgear if the NEC recommended distance is not possible.
NEC art.450.21 required 1.83 m [6 ft] horizontal from a non-fire resistant enclosure. A completely enclosed transformer [except for ventilating openings] does not require any distance from such an enclosure.

 

[busbar]

ISTR that, in North America, typical listed drytypes have clearance requirements stated either on the label or packed with the transformer.

 

[DamnYankee2]

The transformer manufacturer can recommend the distance needed for proper ventilation. An ABB standard dry type requires 24" front and rear. Depending on the transformer terminations, common practive is to close couple the switch and transformer. This can also be done for the LV equipment as well.

 

[jimioy]

And add NFPA 70E to your research - it will give you safe clearance distances, arc flash boundaries and PPE requirements.

Jimi Young - civilian
184th CES/Electrical Shop
Ks Air Nat'l Guard
McConnell AFB, KS