Transformer Fire Safety Protection

[Qurrat]

Hey Everyone!
Can someone please shed light on the fire safety requirements of a power transformer, bearing the following in mind:
Transformer size >= 600 MVA being used in a Power Station

Kindly answer the following queries:
1. What will be a better option from the following two?
a. Conventional Fire Protection System along with Real Time Online Monitoring of DGA (Dissolved Gas Analysis), PD (Partial Discharge) and C&DF (Capacitance and Dissipation Factor)
b. Nitrogen Injection System
2. What is the possibility of failure of Nitrogen Injection System? Can anyone relate practical examples/incidents of Nitrogen Injection System’s accidental operation/ malfunctioning in field? What was the downtime, and associated financial implications?
3. Are there any other possibilities/ options for transformer fire safety and protection?

 

[prc]

1) Fire protection is a must for such large critical unit near to generator-turbine building.

2) Both systems mentioned by you are widely used. Both-water mulsyfire &nitrogen injection- are effective to some extent. I could not find any superiority for any method.Most important is the fire detection method to actuate the nitrogen release or water deluge. How fast and reliably this can be done? That decides the effectiveness of the fire protection system. Some of the new detection methods tried are (a) arc detection inside HV bushing turrets, fast acting pressure detection relay etc.

3) Some new methods tried or developed are use of water mist (enveloping fire by a water mist that cools down the fire and extinguish it) and cover the transformer by a chamber with oxygen level around 14 %. In that level of oxygen,people can move around,but flame will be extinguished due to low level of oxygen.

4) More than anything, new thinking is fire proof transformers - use of dry type bushings (RIP), avoid line end OLTC ( or maintain oil in arcing chamber meticulously),rupture resistant tank etc, etc. Transformer fires are due to any of these three sources + failure in oil filled cable box.

 

[cuky2000]

Both systems are supplementary to each other to reduce the risk of failure of critical transformer assets. Let's keep in mind that Risk = Probability x Consequence.

PREVENTIVE MAINTENANCE: Either manually or real-time monitoring is the first line of defense for fire prevention. This starts installing a good product with an effective electrical fast protection follow by implementing a preventive testing and maintenance program.
_{BPA Experience: After installing faster HV breakers and relays, catastrophic failure of power transformer tank stoped.}

OVERPRESSURE RELEASE: In the event of a catastrophic failure with tank rupture, a proper venting design or additional installed active fire suppression systems such as a Nitrogen Injection System (Sergi System) could be helpful in preventing fire and explosion of power transformers. Nitrogen Injection Fire Protection System (NIFPS) is a fire protection system that prevents oil tank explosion or rupture and possible oil fire in the event.
_{NOTES:
a) NIFPS installation in the Electric utilities and IPP's is uncommon. However, for applications such as oil-filled transformers and reactors substation mounted in an offshore platform, fire suppression is a major concern.
b) Transformers' fault is an uncommon event. According to FM Global’s loss statistics show that it is about 10 times more likely for a transformer to fail without a resulting explosion and fire.}