Fires in electrical transformers

[Peter Wilkinson]

With regard to design standards, NFPA 750:2000 is the most appropriate standard to use.

[Ashley Wood]

You are correct Peter, NFPA 750 2000 is probably the best design standard available at the moment, but it is more of an installation guide rather than a design guide. There will be a new CEN standard issued soon which mirrors 750.

Regards

Ashley

[pyroshield]

Gary,

While CO2 with correct lock off facilities remains a solid choice, perhaps you could look to agents such as Pyrogen, or Pyrostorm, these are areosol and dry powder generators respectivly and are both highly effective and cost effective for this application.

Please let me have your e-mail address for further information

regards

carl shuker

[kurnal]

Have come across a distribution centre which has three 11kv oilfilled, shallow bunded substations in plant rooms enclosed in 1hr protection. The standard high hazard sprinkler system extends into the substations with standard spray pattern heads.

My gut tells me this is a problem but have been looking for justification to back this up.
Whilst BS5588 part 12 recommends high velocity water spray systems for oil filled electrical equipment,  para 5.1.2 of EN12845 (Necessary Exceptions) is not specific-
"areas, rooms or places where water discharge might present a hazard."

I thought there was some more specific guidance somewhere but cant put my finger on it.

Anybody help please?

[John Webb]

kurnal,
BS 5306 Pt2, 5.4.5 says "...where oil and flammable liquids are stored or used in such quantities, and in  such a manner, that standard sprinkler protection may not be effective shall be classified as oil and flammable liquid hazards." The following commentary then recommends the use of a deluge installation with medium or high velocity sprayers.
It does seem to me that even a high hazard standard sprinkler system will not provide the correct water droplet size to deal with an oil fire - all it will do on actuation will be to start filling the shallow bund leaving less room for any spilt/burning oil. So I think your gut reaction is probably correct.

[IrishFire]

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

Hi Gary,

I have used argonite on a simillar site, just finished it last week in fact. The company I've done it for a very happy about using it so much so that they have asked us to quote for several other sites too. (you ex Tyco by any chance??)

Regards

[Ashley Wood]

This will set the cat amongst the pigeons. I was told that there is a height and temperature limitation on the use of inert gas? Any one know anything abut this?

[M,M&M]

Is a transformer a fire hazard?
Should a 40 year old, 1000 kVa transformer sited on the ground floor of a privately-owned high-rise have a fire protection system?  
The transformer is not owned by the building; it supplies the building and some surrounding areas. It currently has no fire protection system.
Any thoughts greatly appreciated.

[AnthonyB]

If the compartmentation is adequate, you don't always need one as a fire, rare in the first place, will remain contained until detected & extinguished.

If it's oil filled and of that vintage in a high rise I am surprised in doesn't have something - a lot of stuff of that vintage has/had a CO2 installation, mostly a rudimentary fusible link & weights system, although some electromechanical systems that had manual release, lockout of automatic release & indicator bulbs for status are also found - either way look for a very old Pyrene or Kidde CO2 Totem on the door.

Originally Methyl Bromide was surprisingly widely used, but in the 50's a national phase out programme began to replace it with CO2, which was successfully completed by the 60's.

The only remaining MB installation I have ever found was in a former Distillery outside of Glasgow & had me reaching for the escape set (it really is that toxic), but on closer inspection the distillery had simply retained the original installation, but had GFA refill the cylinders with BCF - obviously cheaper for them than ripping out & putting CO2 in.

When I find these systems because I cannot usually get in to check it I have various worries:
- Is it ever maintained? (I doubt it, most will be well out of test date on the cylinders)
- Even if functional, they usually have no alarm, not even locally so you would not realise you had a fire & subsequent discharge - a detector head to the buildings alarm (if not a flat block) is probably better
- Is it still there - the totem may still be on the door, but no guarantee the installation hasn't been ripped out

[kurnal]

I have managed to get two of these shifted in my career. I believe in the wrong place they are a huge hazard. If they are general area substations as mine were then the owner of the building may well be able to evict the transformer with a bit of gentle persuasion against the supply company.

The most recent one I dealt with was in the basement of a famous heritage building, underneath the unprotected timber floor of the most important room in the building. I showed the estate manager a few pics and videos of substations on fire. That did the trick a bit smartish!!!! When he first approached the electricity company they wanted big money to move it. He asked them to underwrite a guarantee and then they spirited it away like magic.

Just another thought- the LPC design guide would ask for 4 hours fire protection which could be another way forward. Is there an oil test and change regime in place? If not there could also be an explosion hazard

[Clevelandfire]

Use of atomised water mist can be used on electrical installations succesfully - nothing mad about that at all

If you want mad then this is mad:

"Under various sections of The Electricty (Regulation and Supply) Act 1983  it is an offence to allow a box of frogs with limps to worry the Queens corgis or to fire photon torpedo bursts in Watford without prior consent"

[AnthonyB]

Several of the one's I see that are accessed internally only have at best half hour doors or vented non rated doors - as for floors we can rearely check this as only the electricity board have a key.

How often do they fail & why? A lot of people seem to overlook their presence & resultant risk in a building and can't be bothered to push for evidence from the electrical company that the CO2 system is serviced nor link it to the fire alarm

[kurnal]

Not likely to fail and those in buildings and protected from the weather used to e considered a lower risk than those outside as the oil is less likely to decompose.

But the consequences of failure are extreme. In my operational career of 31 years I attended about 6 explosions and fires in transformers of various sizes from the small 11kv pole mounted transformer to a 266kv supergrid installation. Mostly local area 11kv outdoor transformers. These tend to have sheds built round them these days.

so its one of those liklihood x consequence judgements.

[Ashley Wood]

M&M, I agree with others regarding the hazard. Only in exceptional circumstances would I be happy to have this in a residential block without an extinguishing system. Co2 is fine but only as long as the room is air tight. Working in a Co2 protected space is an issue so you would have to build in several safety measures. High pressure water mist works well, National grid use these systems at some locations I have worked on.

A question that comes up all the time is regarding competency. Do you feel comfortable with the task you have been set and feel  'competent' to perform a fire risk assessment for this type of hazard? This is not a dig at you, its a specialist area and you may want to go out to a specialist consultant/assessor. If your happy and competent with the task then no problem.

[M,M&M]

Many thanks to those who have responded so quickly.
AshleyW I am certainly not competent in this area, and don't mind admitting it, so no offence taken. I'm trying to work out my best next move; setting aside the noise nuisance, when the transformer isolating mounting pads compress and the building hums like a tuning fork to at least the fifth of 16 floors!
AnthonyB according to Central Networks there is no fire protection system. As for "compartmentalisation" all sides of the box (which is one quater of the ground floor, the other 3/4's are occupied flats.) are concrete, apart from the 5m ish frontage, which is wooden louvres which were once open to the elements, but now have, what can only be described as plywood, fixed to their rear. I'm assuming this was done in the past to stop noise transmission? The enterance door to the substation is a matching part of the louvred frontage. There is a fire exit door leading out from another part of the box, with a push bar on the inside, this leads, via a 3m passage and through another door, to the lift lobby area of the ground floor containing three front doors.
Kurnal I have asked for a quote for it to be moved, as we have space, but as you say, it was substantial quote! The LPC design guide 4hr sounds interesting though. I have seen vans with oil drums on, so I assume there is an oil change regime in place. Would anyone suggest someone who might cover Birmingham for a FSRA of the building to include the substation? If so I'll email with additional info
Many thanks, once again, for such a prompt response to this issue.