---
title: "Major components of a power station and functions"
subject: "Power System Analysis I"
chapter: 1
key: "semester_4/power_system_analysis_i:power-station-components-functions"
source: https://www.bctengineer.com/q/semester_4/power_system_analysis_i/power-station-components-functions
site: BCT Engineering
---

# Major components of a power station and functions

Power System Analysis I · Chapter 1: General Background

- Asked in: 2072 Asoj, 2+4 marks
- Video: [Power Generation | Eaton PSEC](https://www.youtube.com/watch?v=ZSCEfJ4TXW4) — Eaton
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/power_system_analysis_i/power-station-components-functions
- Whole chapter: https://www.bctengineer.com/md/semester_4/power_system_analysis_i/chapter-1

## Question

Enlist the major components of an electric power station. Describe in brief the functions of any four major components.

## Short answer

Major components include prime mover, alternator, excitation/AVR, step-up transformer, busbars, switchgear, relays, CT/PT, lightning arresters, auxiliaries, control room and earthing. Alternator converts mechanical to AC; AVR controls voltage; transformer raises voltage; breakers with relays isolate faults.

## Answer

#### Major components of an electric power station
1. Prime mover (turbine) with governor
2. Alternator (synchronous generator)
3. Excitation system and AVR
4. Generator step-up transformer
5. Busbars
6. Switchgear: circuit breakers, isolators, earth switches
7. Protective relays, CTs and PTs
8. Lightning arresters
9. Station auxiliary transformer and auxiliaries
10. Control room, metering, SCADA and battery (DC) system
11. Earthing system

#### Functions of four major components
**1. Alternator**
- Converts mechanical energy from the turbine into 3-phase AC electrical energy, usually at 6.6–11 kV.
- Its speed fixes the frequency: $f = PN/120$.

**2. Excitation system with AVR**
- Supplies DC current to the rotor field winding.
- The automatic voltage regulator varies this current to hold terminal voltage and to control reactive power output.

**3. Step-up transformer**
- Raises generator voltage to transmission level (e.g. 11/132 kV), reducing current and line losses.
- Isolates generator from the transmission network.

**4. Circuit breakers with protective relays**
- Relays (fed by CTs and PTs) sense abnormal conditions such as short circuit, overload, earth fault, loss of excitation.
- The breaker automatically opens to isolate the faulty part, protecting equipment and keeping the healthy system running; it is also used for normal switching.

```text
 Turbine--[G]--[CB]--[11/132 kV Tx]--[CB]--[Bus]-->Lines
            |                            |
         Exciter/AVR                 CT, PT, LA
```

## Check yourself

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

1. The frequency of an alternator is fixed by which relation?
   A. f = 120/PN
   B. f = P/N
   C. f = PN/120
   D. f = N/(120P)
   Answer: C. f = PN/120, where P is poles and N is speed in rpm. (Key point: Alternator frequency)

2. What does the AVR do?
   A. Varies the rotor DC field current to hold terminal voltage and control reactive power
   B. Controls turbine speed
   C. Opens the breaker on fault
   D. Steps up the voltage
   Answer: A. The AVR adjusts excitation, which regulates voltage and Q output. (Key point: Role of excitation and AVR)

3. Why is a generator step-up transformer used?
   A. To raise current
   B. To make frequency higher
   C. To generate DC
   D. To raise voltage to transmission level, reducing current and line loss
   Answer: D. Higher voltage means lower current and thus lower loss; it also isolates generator from the network. (Key point: Step-up transformer function)

4. What is the job of protective relays with circuit breakers?
   A. Increase fault current
   B. Regulate frequency
   C. Sense abnormal conditions and trip the breaker to isolate the faulty part
   D. Supply DC to the rotor
   Answer: C. Relays fed by CTs and PTs detect faults and the breaker opens to isolate them. (Key point: Relays and breakers)

## Related in Power System Analysis I

- [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×
- [Typical power system network and components](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Atypical-power-system-network-components) — Power System Analysis I, chapter 1

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