We are looking to install a transformer fire barrier between two of our main incoming transformers (34.5 KV to 13.8V) at our substation that feed power to our facility. The fire barrier will be of a concrete masonry unit (CMU) type. There is a single containment for these two transformers and there is a cable tray that runs between the two transformers for protective relay controls. As a result of the tight distances between the transformers and the cable tray, the fire barrier (CMU) will be within 4 feet of the high voltage cables (34.5KV,13.8KV). The CMU will be grounded to the ground grid. The concern we have is that there is not enough distance between the barrier and the overhead transformer power lines and could cause an issue with there being a conductive path from the transformer lines through the fire barrier. Does anyone have any experience with this application and insight into if this setup is approved/allowed within NFPA70 and NFPA850 code?
Transformer Fire Protection Barrier
- Thread starter ROHM
- Start date
JoeStillman
Senior Member
- Location
- West Chester, PA
The National Electric Safety Code has guidelines for conductor clearances. Rule 234C1 says, for 34.5 kV class, 9.2 ft clear at rest and 6.2 ft clear displaced by wind. This info is available to the public in table 5-1 of this document.
Last edited:
mehdi1351
Member
- Location
- New Zealand
- Occupation
- Electrical Engineer
Hi, I have the same question. I am going to install 2 transformers with 3MVA rating for our plant in Texas and I am wondering to know whether we need to install any fire-rated barrier between them as per NEC code?
JoeStillman
Senior Member
- Location
- West Chester, PA
The NEC will not have anything to say about substation transformers. You have to use your engineering judgement to decide if the cost is warranted.
If the reason you have two transformers is for redundancy, then physical separation is a good idea. If it's just to get 6 MVA of capacity, then maybe not