Fires in electrical transformers

[Gary Howe]

Can anyone tell me what is the most common method for protecting a set of transformers and the associated 11KV switchgear situated in a basement plant room?

The room is currently protected by an old CO2 system, which is due to be replaced out, what would be recommded as suitable alternative extinguishing medium to protect such a risk?

Thanks


Gary

[Allen Higginson]

We would still quote for CO2 for generator or Transformer bays but using the same control equipment as we would in FM200/HiFOG systems.

[AnthonyB]

Nothing wrong with keeping CO2. Many subs still have them, although often they are the mechanical pull station/fusible link ones (which still work more than adequately if maintained), if you are lucky it may be a rudimentary electromechanical one.
I've seen the following done with existing subs:
1) Rip all existing stuff out & have nothing but AFD & PEA
2) Leave existing system in unaltered (with out of test cylinders)
3) Keep existing system, ensure all cylinders are within test date having them retested as required
4) Emulsifying water sprinklers installed (more recently water mist is being used instead)
5) Clean agent gas system, eg. Argonite, Inergen, FM200

Rarely you'll find a sub with BCF, only found that twice, in one case it was an old Methyl Bromide system where GFA refurbed the cylinders to to BCF in the late 60s

With existing basement subs refurbing the existing CO2, having nothing, or clean agent are the most common i've seen.

New subs mostly have nothing other than AFD/PEA, the few that have anything are Water Mist or Clean agent

[Owen66]

Gary,

If this is a proposed installation consider the use of SF6 switchgear and Cast resin transformers. If you need "oil tx's" look  for Midel or similar.

I have recently used "argonite" in  similar circumstances for a hospital scheme.

Be careful about retaining CO2 as it presents some risks to persons present.

Regards

Owen

[Allen Higginson]

I can appreciate the move away from CO2 due to the risk to those in the area but if the correct procedures are followed (manual only when area occupied,preferrably linked to the door lock) and the system is designed correctly (delay of actual discharge upon signal to discharge,good audible and visual indication) then it is a good solution.

[Owen66]

Agreed it can be a good solution but many RECs are recommending removal following risk assessment. If this is a private sub station I would suggest the same risk assessment procedure and use a less "agressive" solution

Owen

[Ashley Wood]

Can anyone tell me what is the most common method for protecting a set of transformers and the associated 11KV switchgear situated in a basement plant room?

The room is currently protected by an old CO2 system, which is due to be replaced out, what would be recommded as suitable alternative extinguishing medium to protect such a risk?

Thanks


Gary

[Ashley Wood]

Gary,

Take a look at high pressure water mist systems. These systems use very small amounts of de-mineralised water stored in cylinders. Because the droplets are so fine i.e 60-100 micron, they do not form a 'bridge' for an electrical discharge. I know of one manufacturer that has had there system tested upto 33kva with no effects.

A small amount of water is required to achieve a result. Also, the system has the ability to 'smoke wash'. This effect will reduce the amount of smoke produced by simply 'washing' it to the floor.

I have been involved in hundreds of water mist system designs and installations, if I can help, just ask.

[Chris Houston]

Gary,

Take a look at high pressure water mist systems. These systems use very small amounts of de-mineralised water stored in cylinders. Because the droplets are so fine i.e 60-100 micron, they do not form a 'bridge' for an electrical discharge. I know of one manufacturer that has had there system tested upto 33kva with no effects.

A small amount of water is required to achieve a result. Also, the system has the ability to 'smoke wash'. This effect will reduce the amount of smoke produced by simply 'washing' it to the floor.

I have been involved in hundreds of water mist system designs and installations, if I can help, just ask.

Ashley,

Would such a system be designed to any British or European Standard?

[Allen Higginson]

http://www.hifog.com/en/land/index.htm (manufacturers)
It has FM and German Loss Prevention approval.We have offered it as an alternative also and we may have been the installers at London Underground (but don't quote me - I'm over in the wilderness here and depend on pigeon post for info!!!).

[Ashley Wood]

The approval situation depends on the manufacturers. The two leading systems are Fogtec and Marioff, I have worked with both. I know that Fogtec have an independant test report with details of tests upto 33Kva & I believe Marioff have one upto 11Kva. Take a look at the FM Global web site for manufacturers approvals. As far as I aware, there is no euro, standard writen to test to so far.

Best regards

Ashley

[Ashley Wood]

Fogtecs web site is www.fogtec.com

[Ashley Wood]

Regarding design standards. The system design depends on the manufacturers equipment. The manufacturers design would be based upon tests that have been done. These tests will dictate the K-factor for the nozzle, the distance from the wall, height above risk, distance between nozzles etc.

[Owen66]

Ashley,

A minor point but the voltages you quote are Kv (Kilovolts) not Kva (Kilovolt amperes). Essentially KVa is a power rating not a voltage rating.

Regards

[Ashley Wood]

Have a look at Fogtec or Hi-Fog. Both of these systems use pure water for this type of application. Yes, I did say water and No I am not MAD!

These systems use atomised water mist to achieve fantastic results.
Best regards

Ashley