Transformer Fire Protection

[MechProjectEng]

Hi all,

Hoping for some advice:

We have a recently constructed substation. The substation is a stand alone and unmanned building consisting of 3 rooms: HV Switchgear Room, LV Switchgear Room and Transformer Room. Overal size of substation is 25m x 10m. Concrete frame building.

Two walls of the transformer room are exterior walls of the substation. These walls have cluster block/air brick blockwork, and the doors to exterior are wire mesh gates. I.e. the transformer rooms are naturally ventilated, and are effectively open to the external environment. The other two walls (between transformer room and HV/LV switchgear rooms) have 2 hour fire resistance, and there is also a concrete roof slab overhead.

The transformer room houses two (2) 1250kVA transformers and one 2500kV transformer. All are oil filled with mineral oil. There are no separation walls between the transformers.

It seems our designer had not fully considered the code requirements, and as the substation has already been constructed, our AHJ has provided us with the following options:

-Add a deluge system.
-Replace the mineral oil with an approved 'less flammable' oil.

Both options are problematic for us.

The deluge system option has a fairly major problem of drainage, due to some cable trenches which link the transformer room to the switchgear rooms, which would be practically very difficult to seal to prevent flooding.

The implication of changing the transformer oil is that the transformers may have to be de-rated, having electrical implications on our process, and the other problem is that the transformers apparently have to be shipped back to the factory (overseas) to have the oil replaced and be re-tested.

I would appreciate any comments you may have, including:
-The code requirements for our particular type of installation; stand alone substation, unmanned etc. Does the code actually require a deluge system in this situation?
-Does anyone have any alternative options/ideas which we could discuss with our AHJ.

Thanks in advance.

 

[cdafd]

Did they give you a code section requiring protection int the first place???

If so what book, section, edition????

 

[MechProjectEng]

I have been referred to NFPA 70 450.26 which talks about oil filled transformers installed indoors. Yet it is unclear to me what aspects are applicable in our situation, where we have an unmanned stand alone substaiton.

 

[cdafd]

82 x 32 2,624 sq ft and they want fire protection???

are the buildings there more for weather protection than anything????


not sure what edition of 70 they are using, from 2011 edition



450.26 Oil-Insulated Transformers Installed Indoors.Oil-insulated transformers installed indoors shall be installed in a vault constructed as specified in Part III of this article.


Exception No. 1: Where the total capacity does not exceed 112 1/2 kVA, the vault specified in Part III of this article shall be permitted to be constructed of reinforced concrete that is not less than 100 mm (4 in.) thick.



Exception No. 2: Where the nominal voltage does not exceed 600, a vault shall not be required if suitable arrangements are made to prevent a transformer oil fire from igniting other materials and the total capacity in one location does not exceed 10 kVA in a section of the building classified as combustible or 75 kVA where the surrounding structure is classified as fire-resistant construction.



Exception No. 3: Electric furnace transformers that have a total rating not exceeding 75 kVA shall be permitted to be installed without a vault in a building or room of fire-resistant construction, provided suitable arrangements are made to prevent a transformer oil fire from spreading to other combustible material.



Exception No. 4: A transformer that has a total rating not exceeding 75 kVA and a supply voltage of 600 volts or less that is an integral part of charged-particle-accelerating equipment shall be permitted to be installed without a vault in a building or room of noncombustible or fire-resistant construction, provided suitable arrangements are made to prevent a transformer oil fire from spreading to other combustible material.



Exception No. 5: Transformers shall be permitted to be installed in a detached building that does not comply with Part III of this article if neither the building nor its contents present a fire hazard to any other building or property, and if the building is used only in supplying electric service and the interior is accessible only to qualified persons.



Exception No. 6: Oil-insulated transformers shall be permitted to be used without a vault in portable and mobile surface mining equipment (such as electric excavators) if each of the following conditions is met:


(a)
Provision is made for draining leaking fluid to the ground.


(b)
Safe egress is provided for personnel.


(c)
A minimum 6-mm ( 1/4-in.) steel barrier is provided for personnel protection.

 

[MechProjectEng]

Thanks cdafd,

Yes, AHJ asking for fire protection for this size of unmanned building.

Yes, this is one of the clauses.

I tried to argue that we could use exception No.5 as we have a detached substaion building. But the AHJ argued that this is not a deached building as the HV and LV switchgear rooms are in the same building.

When using the vault definition, I understand that we cannot classify our transformer room as a vault, as we have cluster block/air brick in the exterior walls.

Yes, for the transformer room, the roof and walls are only for weather protection.

Can you advise any route to take to justify not requiring the fire protection?

 

[stookeyfpe]

I'm unsure where you are but in my state utility transformers are under the authority of the State Public Utility Commission. We have high-rise buildings in my town with large vaults with no sprinkler protection. In fact, neither the owner or firefighters have keys to these rooms.

Your governmental authority over utility power systems may take precedence over the community's fire code.

 

[cdafd]

what Stookey said!!!

also out of the international fire code:::

903.3.1.1 NFPA 13 sprinkler systems. Where the provisions
of this code require that a building or portion
thereof be equipped throughout with an automatic sprinkler
system in accordance with this section, sprinklers
shall be installed throughout in accordance with NFPA
13 except as provided in Section 903.3.1.1.1.
903.3.1.1.1 Exempt locations. Automatic sprinklers
shall not be required in the following rooms or areas
where such rooms or areas are protected with an
approved automatic fire detection system in accordance
with Section 907.2 that will respond to visible
or invisible particles of combustion. Sprinklers shall
not be omitted from any room merely because it is
damp, of fire-resistance rated construction or contains
electrical equipment.
1. Any room where the application of water, or
flame and water, constitutes a serious life or fire
hazard.
2. Any room or space where sprinklers are considered
undesirable because of the nature of the
contents, when approved by the fire code official.
3. Generator and transformer rooms separated
from the remainder of the building by walls and
floor/ceiling or roof/ceiling assemblies having
a fire-resistance rating of not less than 2 hours.
4. Rooms or areas that are of noncombustible constructionwith
wholly noncombustible contents.
5. Fire service access elevator machine rooms and
machinery spaces.

 

[Sdpaddler50]

Transformer fires can be a beast when large amounts of hydrocarbon based oil are present. Arcing faults within the coils literally cause an explosion of burning oil when these things blow. Its a real threat. On the other hand, sounds like you have a relatively low value, stand alone vault, so I do understand the arguement you are making.

Couple comments:
-Retrofitting with a less flam oil, like FM approved fluid is very difficult for electrical compatibility reasons. Great idea for new installations, but I have never heard of it being done on a retro basis.
-Sprinklers are a good protection choice (when needed). Typical wet, closed head systems are often sufficient. Deluge systems are generally used for the very large units, 4160V, and often these are outside so you dont have the drainage issues.
-If push comes to shove, another option you could consider if this is a normally unocuppied space is Co2. With the required pre-discharge warnings, etc, (as outlined in NFPA 12 if i remember correctly) this can be effective. It is even used on very large arc furnace transformers (AFT's) in steel mills. The AFT is normally in an unmanned, concrete vault, so CO2 is viable. Yes, sprinklers/water is the best solution, but C02 is an option.

 

[cdafd]

The op indicates the room is not enclosed

The building is just there for weather protection.

 

[cdafd]

This is out of the international fire code the chapter dealing with hazardous materials

2704.13 Weather protection. Where overhead noncombustible construction is provided for sheltering outdoor hazardous material storage areas, such storage shall not be considered indoor storage when the area is constructed in accordance with the requirements for weather protection as required by the International Building Code.

 

[stookeyfpe]

The original poster hasn't responded so we've given him/her everything she/he needs.

 

[MechProjectEng]

Stookey: Thanks. I'm based in the middle east, not in the US, and the authority does fall with our AHJ in our case.

cdafd:Internatinoal Fire Code 903.3.1.1.1 - Exception 4 may be applicable to us. 2704.13 Weather protection - Will also investigate this avenue as to whether it can be reasoned that the area is 'outdoor'.

sdpaddler: Thanks for the advice and other options for consideration. A wet closed head sprinkler system may well be a good compromise with our AHJ (if needed). This would alleviate our drainge problem. CO2 will not work in our case as the room is open to exterior (wire mesh gates and clusterblock walls).

 

[cdafd]

4 yes but the fluid is combustible

I thought 1 or 2??

 

[MechProjectEng]

Doh! Yes of course. Though 1 and 2 may also be difficult to argue as the transformers are 'outdoor' spec (IP55) transformers, and also our AHJ would like to trip the upstream breaker when the sprinkler/deluge is activated.

 

[cdafd]

Do other fairly new set ups like this have fire protection systems installed, around your area?????

 

[chicopee]

If fire protection is a must, then have a chemical extinguishing system instead of water; basically a system simular to automatic chemical extinguishing systems covering fryolators and grills in commercial cooking facilty.

 

[MechProjectEng]

cdafd: Most other oil filled installations in the area are installed outdoors in fenced compounds. Some (typically larger) installations are equipped with deluge systems, but not all.

chicopee: Thanks, I will look into chemical extinguishing. I don't know much about this.

 

[Sdpaddler50]

The most common/accepted approach to protect these is water since the hazard is a combustible liquid ; closed wet head system for smaller units, and larger, open head deluge for the big, high voltage systems normally in yard areas. CO2 is also an accepted method, but rarely used. I have never heard of, or seen a dry chemical system. If you are referring to a dry chemical powder type extinguisher, these make a mess when discharged and dont get along with electrical systems very well. For example, a small computer room should have clean agent portable fire extinguishers hanging on the wall, not dry chemical for the same reason.

 

[stevenal]

FR3 is less flammable, recommended for retrofilling, and makes tasty fries

http://www.spxtransformersolutions....0-2FR3fluidretrofillguide-Sept2006CPS_001.pdf

 

[DavidCR]

Hi"mech" and everybody.

1.
First, if you already haven´t, I´d recommend you to download IEEE979, IEEE980, and Reclamation´s "Facilities Instructions, Standards, and Techniques Volume 3-32" Transformer Fire Protection (

http://www.usbr.gov/power/data/fist/fist3_32/fist3-32.pdf)

or just Google "reclamation transformer fire protection". Also consider NFPA 850/851. These docs include most of the criteria dealing with oil transformers. Dealing with this the need is not in NEC.

2.
If you cannot hold a deluge system water spill, you could be having troubles with oil containment as per IEEE 980. Your AHJ should be giving more importance to oil spill installations, than to deluge system requirement. The deluge system is a relatively useful protection, but good oil containment is a really important difference. And if you cannot accomplish basic oil spill requirements, how will you know if in case of a disaster the insurance company will pay for the losses, or the owner will be issued for operating with a dangerous non standard installation.

3.
I´m not sure but I think you have not mentioned two important aspects:
-Volume of oil. Most deluge system requirements are based on the quantity of oil you have, you decided to operate with the good old mineral oil so you have to take care of it. A point to remember: even transformer oil is a high flash point liquid, in a fire it is sprayed and it is potentially explosive, and releases lots of heat.
-Whats nearby, depending on that, I´ll endorse or not any requirement from your AHJ.
-The importance of the substation for your company.
These aspects will help you to sell the idea of protection investments.

4.
Anyway. A deluge system, even it is a directly accepted protection for transformers, is a problem on unmanned facilities: it will go off and nobody stops the water, it has to be tested will actual discharge, etc. "If you cannot test it, how will you know if in case of a disaster the insurance company will pay for the losses".
If you don´t have water in good quantity and pressure, and you don´t have someone to supervise and maintain the deluge, system, I will say it is not a good recommendation from you AHJ, the standards recommend the deluge system as a useful help to reduce losses but it is not a complete solution.

5.
Options for active fire protection order of relatively cost, if accepted by your AHJ:
- Aerosol dust protection (search for Aero-K, Stat X), small transformers could be a good application for this type of system. In your case you should analyze if this is an option form you.
- CO2. But the place should be closed.
- Dry chemical.
- Water Deluge. Do you have water and pump for this?
- CAF foam system.
- Water mist.

6.
Passive protection. You may ask if your AHJ will have a different position if you invest on good oil containment and good fire stopping systems. And effective ways to isolate, smoke, flames, spills, heat all around the enclosed area.

7.
Explosion risk protection. Think of a "Transformer Protector"/SERGI system. Maybe your local AHJ will be happy if you at least you eliminate the risk of a violent fire explosion, some companies give a lot of importance of this type of protection and is referred by NFPA. It is not a general transformer fire protection but a tested protection for arc-fault explosions.

8.
For the next time: give lots of importance to distances, separations, oil containment. These in general eliminate the need of fire suppression means.

Hope this helps.