Transformer Fire detection and protection system 1

[saadmuhammad]

Is it necessary to trip transformer before deluge operation?
what is the recommendations of NFPA standard on that issue?

 

[cranky108]

I don't know about the NFPA, but spraying water on a transformer that is energized in a dry, or salty environment, could actually create a fault.

 

[RRaghunath]

In case of actual fire incident, transformer would have been already tripped by the protections.
If the requirement is to test the deluge system, this can be done when transformer is live provided one is sure that
# there are no exposed power terminals and the cable boxes are tightly closed,
# all the terminal boxes (like that of Buchholtz, PRD etc.) are tightly closed and there is no risk of water entry
# Marshaling box / Thermo-unction box / OLTC DM cabinet etc. are all properly closed.
I have seen the deluge system tested on live transformer.

 

[thermionic1]

Many years ago, the system of a very large city saw the consequences of run to failure maintenance policies. In a particular substation with a large ring bus and 4 transformers, the transformers were failing due to age, neglect and a heat wave. After 2/4 transformers failed, the fire department was called into spray down the existing transformers. I got paid to babysit the firemen. The spraying lasted for about 72 hours and then the heat wave subsided. The 2 remaining transformers lasted until the entire station was rebuilt. They were avoiding the bushings and aiming for a vacant spot on the tank with the water.

 

[cranky108]

Unfortunately transformers don't have a soaker hose rating.
Run to failure is practiced by many utilities, and is a common practice. Only recently have PUC's realized that discouraging utilities from keeping spare equipment (allowing them to capitalize it) is not in the best interest of customers.
NERC is now. in a backwards way requiring utilities to keep spares of long lead time equipment.

Whenever a company replaces working equipment because of age, they leave money on the table.

 

[low1]

In our utility, we do functional flow tests on the transformer deluge while the transformer is energized regularly. These are tailrace deck mounted generator step up transformers 13.8kv (in enclosed iso-phase bus through the wall) to 138 or 230kV depending on the plant, exposed aluminum bus. Years ago, prior to replacing the transformers on one plant, it was actually an operating directive to turn on the deluge if the winding temperature was approaching trip levels on hot days in the summer to limp them through prior to replacement. Nozzles are all broken stream, heavy mist