---
title: "Emergency power supply system for industry"
subject: "Industrial Power Distribution and Illumination"
chapter: 9
key: "semester_6/industrial_power_distribution_and_illumination:emergency-supply-system-industry"
source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/emergency-supply-system-industry
site: BCT Engineering
---

# Emergency power supply system for industry

Industrial Power Distribution and Illumination · Chapter 9: Emergency and Backup Supply Systems

- Asked in: 2074 Bhadra, 4 marks; 2073 Bhadra, 4 marks (asked 2 times)
- Video: [Emergency Power Supply System](https://www.youtube.com/watch?v=S9YGG3_PitE) — Amgad Mazen Elseaidy
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/emergency-supply-system-industry
- Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-9

## Question

Explain about emergency power supply system for an industry.

## Short answer

An emergency power supply system automatically provides power to essential industrial loads (lighting, fire protection, controls, critical processes) when utility supply fails. Sources include batteries, UPS, diesel generators with AMF panels, or a second utility feeder, with automatic changeover and separate essential bus.

## Answer

An **emergency power supply system** is an independent source that automatically supplies essential loads of an industry when the normal (utility) supply fails, to protect people, equipment and critical processes.

#### Need / loads served
- Emergency and escape lighting, exit signs.
- Fire alarm, fire pumps, smoke extraction, lifts.
- Control and protection circuits (switchgear tripping, PLCs, instruments).
- Critical process loads where a sudden stop causes danger or loss (furnace cooling, chemical stirring, compressors).
- Communication systems and security systems.

#### Sources
1. **Battery systems** – central battery or self-contained luminaires; instant supply.
2. **UPS** – no-break supply for computers and controls.
3. **Diesel generator set** with **automatic mains failure (AMF) panel** – starts in 10–15 s, supplies large loads for long periods.
4. **Second independent utility feeder** with automatic changeover.

```text
 Utility ──►[ATS]──► Essential bus ──► Emergency loads
              ▲
 DG set ──────┘
 Battery/UPS ───────► Critical loads (no break)
```

#### Main features
- Automatic start and changeover (ATS/AMF).
- Essential loads on a separate bus, separated from non-essential loads.
- Batteries kept charged by float/trickle charger.
- Regular testing and maintenance of DG and batteries.

## Check yourself

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

1. What is the function of an emergency power supply system in an industry?
   A. Independent source that automatically supplies essential loads when the utility fails
   B. Increases utility voltage permanently
   C. Supplies all loads manually at all times
   D. Replaces utility supply for cost saving
   Answer: A. It protects people, equipment and critical processes during mains failure. (Key point: Purpose)

2. Which source gives a no-break supply and which starts in 10-15 s?
   A. DG set is no-break; UPS starts in 10-15 s
   B. UPS/battery is no-break; DG set with AMF starts in 10-15 s
   C. Both are no-break
   D. Both take minutes
   Answer: B. Batteries/UPS are instant; DG sets with AMF panels take 10-15 s. (Key point: Sources)

3. Which load is typically on the emergency bus?
   A. Air-conditioning of offices
   B. Decorative lighting
   C. Escape lighting, fire alarm, fire pumps and critical control circuits
   D. All non-essential machines
   Answer: C. Only essential loads are put on a separate essential bus. (Key point: Loads)

## Related in Industrial Power Distribution and Illumination

- [Importance of emergency supply, online vs offline UPS](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aemergency-supply-ups-importance) — Industrial Power Distribution and Illumination, chapter 9
- [Emergency supply and Ah vs Wh efficiency](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aemergency-supply-ah-wh-efficiency) — Industrial Power Distribution and Illumination, chapter 9
- [Emergency vs back-up supply, online/offline UPS](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aemergency-vs-backup-ups) — Industrial Power Distribution and Illumination, chapter 9, asked 3×
- [Types of power supply system for industrial plant](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aindustrial-supply-system-types) — Industrial Power Distribution and Illumination, chapter 1, asked 2×
- [Emergency lighting purposes and trickle charging](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aemergency-lighting-trickle-charging) — Industrial Power Distribution and Illumination, chapter 9
- [Lighting schemes: local, general, emergency](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Alighting-schemes-local-general-emergency) — Industrial Power Distribution and Illumination, chapter 7, asked 2×

## Related in other subjects

- [Short note: Power supply system](https://www.bctengineer.com/question.md?key=semester_1%2Fbasic_electrical_and_electronics_engineering%3Ashort-note-power-supply-system) — Basic Electrical and Electronics Engineering, chapter 4
- [FACTS and HVDC for Nepal's power industry](https://www.bctengineer.com/question.md?key=semester_8%2Fhigh_voltage_engineering%3Afacts-hvdc-nepal-upgrade) — High Voltage Engineering, chapter 1
- [Fuel supply system of diesel plant](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Adiesel-fuel-supply) — Power Plant Equipment, chapter 5, asked 3×
- [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