Why Transformer Protection ?
Let us take an example to be more specific and clear. In an oil cooled transformer, the oil is likely to catch fire after a certain temperature exceeds and instantly the entire transformer will catch fire and burn from all sides; even though the transformer is made up of metal. To avoid this kind of fire, we use Water Spray System.
Here, there may be multiple metal rings of detectors, a detector is nothing but a temperature sensing element. This detector ring is placed next to the most likely sots where the temperature is about to exceed or fire is about to take place. Also the, entire transformer is surrounded by multiple sprays, at multiple levels. A spray is nothing, but a sprinkler without the temperature sensing, bulb.
When the fire does take place, the detector ring detects this; and gives the signal to the deluge valve or all the sprinkler surrounding the transformer to start all at once. Hence the entire transformer is flushed with water, to cool it down.
In case of fire the Quartzoid Bulb detector (QBD) shall burst at rated temperature due to heat which allow water in the detection pipe to drain out and in process Deluge valve top chamber pressure reduces which inturn allow the Deluge valve to open fully.
As soon as the Deluge valve opens the water shall flow through the piping to flow water to all water spray nozzles mounted on the piping around the transformer. The water shall be sprayed in Hollow conical spray pattern to cover entire area of the transformer so that the fire on the transformer shall cool due to emulsification as well as fire get extinguish due to cutting off oxygen due to coverage pattern of the nozzle.
Also Read: Basics of Deluge Valve