---
title: "Fire fighting system in power station"
subject: "Power Plant Equipment"
chapter: 4
key: "semester_7/power_plant_equipment:fire-fighting-power-station"
source: https://www.bctengineer.com/q/semester_7/power_plant_equipment/fire-fighting-power-station
site: BCT Engineering
---

# Fire fighting system in power station

Power Plant Equipment · Chapter 4: Substation Equipments

- Asked in: 2073 Shrawan, 5 marks; 2082 Baisakh, 5 marks; 2081 Baisakh, 4 marks; 2080 Bhadra, 6 marks; 2073 Chaitra, 4 marks (asked 5 times)
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/power_plant_equipment/fire-fighting-power-station
- Whole chapter: https://www.bctengineer.com/md/semester_7/power_plant_equipment/chapter-4

## Question

Describe the fire fighting system used in power station with necessary diagram.

## Short answer

The fire-fighting system uses smoke/heat detectors and an alarm panel to trip equipment and start extinguishing. Transformer fires are fought with water spray (deluge) to emulsify oil, CO2 flooding protects generators and cable rooms, and a hydrant ring with pumps supplies water. Portable extinguishers and passive measures are also used.

## Answer

The **fire fighting system** of a power station detects a fire early, raises an alarm and puts it out quickly, so that costly equipment (transformers, generators, cable galleries, oil stores) is saved and people are safe.

#### Main fire risks
- Transformer and switchgear insulating oil
- Generator windings (insulation, and hydrogen in large units)
- Cable trenches and galleries
- Fuel oil and coal stores, battery rooms

#### Components of the system

```text
 +--------+   +-------------+   +-----------------+
 | Fire   |-->| Fire alarm  |-->| Alarm (bells,   |
 |detector|   | control pnl |   | lamps) + trip   |
 +--------+   +------+------+   +-----------------+
                     | opens deluge valve
 +-------+  +-------+v +-------+   +-----------+
 | Water |->| Pumps |->|Deluge |-->| Spray     |
 | tank  |  |(el+DG)|  | valve |   | nozzles   |
 +-------+  +-------+  +-------+   | (on xfmr) |
                                   +-----------+
```

1. **Detection:** smoke, heat (rate-of-rise) and flame detectors; for transformers, quartz bulb or linear heat detectors placed around the tank.
2. **Alarm panel:** receives detector signals, sounds the alarm, shows the zone, trips the equipment and starts the extinguishing system.
3. **Extinguishing systems:**
   - **Hydrant system:** a ring main of pipes with hydrant points and hoses, kept pressurised by a jockey pump, with a main electric pump and a standby diesel pump.
   - **Water spray (deluge) / mulsifire system:** for transformers; a high-velocity water spray forms an emulsion on the oil surface, cools it and cuts off oxygen.
   - **CO$_2$ flooding system:** for generators, control rooms and cable vaults; CO$_2$ cylinders discharge automatically and dilute the oxygen. Used where water would damage equipment.
   - **Foam system:** for oil tanks and fuel stores.
   - **Portable extinguishers:** CO$_2$, dry chemical powder and foam types near equipment.
4. **Passive measures:** oil soak pits filled with gravel under transformers, fire walls between transformers, fire-resistant cable coating and fire barriers.

#### Requirements
- Automatic operation with manual back-up.
- A reliable, separate water supply and a standby diesel pump.
- Regular testing of detectors, pumps and cylinders.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the role of the fire alarm control panel?
   A. Receives detector signals, sounds the alarm, shows the zone, trips equipment and starts extinguishing
   B. Stores the water for the hydrant ring main
   C. Generates CO2 for flooding
   D. Only records the temperature of the transformer oil
   Answer: A. The panel is the brain linking detection to alarm, tripping and operation of the extinguishing system. (Key point: Role of the alarm panel)

2. Which system is used mainly for transformers and how does it work?
   A. CO2 flooding: dilutes oxygen in a closed room
   B. Water spray (mulsifire/deluge): high-velocity spray forms an emulsion on the oil, cools it and cuts oxygen
   C. Foam system: used only for coal stores
   D. Hydrant hose: used only with the supply switched on
   Answer: B. Mulsifire emulsifies the oil surface and cools it, which suits oil-filled transformers. (Key point: Transformer protection)

3. Why is a CO2 flooding system used for generators, control rooms and cable vaults?
   A. It is cheaper than water in every case
   B. It cools the oil surface by emulsification
   C. It extinguishes fire without the water damage to electrical equipment
   D. It keeps the hydrant ring main pressurised
   Answer: C. CO2 dilutes oxygen and leaves no residue or water, so it is used where water would damage equipment. (Key point: Choice of CO2)

4. In the hydrant system, what are the jockey pump and diesel pump for?
   A. The diesel pump keeps pressure; the jockey pump supplies foam
   B. Both are used only for CO2 cylinders
   C. The jockey pump is the standby for the detectors
   D. The jockey pump keeps the ring main pressurised; the diesel pump is standby to the main electric pump
   Answer: D. A small jockey pump holds line pressure; a diesel standby ensures water even when power fails. (Key point: Hydrant pumping)

## Related in Power Plant Equipment

- [Requirements of steam power station design](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Asteam-station-design-requirements) — Power Plant Equipment, chapter 7
- [Reactor to protect circuit breaker of small station](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Areactor-protect-circuit-breaker) — Power Plant Equipment, chapter 4
- [SCADA in a power system](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Ascada-power-system) — Power Plant Equipment, chapter 4, asked 4×
- [Function of reactor in power system](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Areactor-function) — Power Plant Equipment, chapter 4, asked 3×
- [Why reactors are used and their types](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Areactor-types) — Power Plant Equipment, chapter 4
- [Function of excitation system and its transfer function](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Aexcitation-function-tf) — Power Plant Equipment, chapter 3, asked 2×

## Related in other subjects

- [Electrification system and fire protection](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aelectrification-fire) — Building Technology, chapter 12
- [Major components of a power station](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Apower-station-major-components) — Power System Analysis I, chapter 1, asked 2×
- [DC supply system in a generating station](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Adc-supply-system) — Power Plant Design, chapter 4
- [Major components of a power station and functions](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Apower-station-components-functions) — Power System Analysis I, chapter 1