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

# Major components of a power station

Power System Analysis I · Chapter 1: General Background

- Asked in: 2070 Magh, 5 marks; 2068 Magh, 3 marks (asked 2 times)
- Video: [Power Plant Explained | Working Principles](https://www.youtube.com/watch?v=HGVDu1z5YQ8) — RealPars
- 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-major-components
- Whole chapter: https://www.bctengineer.com/md/semester_4/power_system_analysis_i/chapter-1

## Question

What are the major electrical components in a power station?

## Short answer

Major electrical components are the alternator with exciter/AVR, generator step-up transformer, busbars, circuit breakers and isolators, protective relays with CTs/PTs, lightning arresters, auxiliary transformer, DC battery bank, SCADA, and earthing system.

## Answer

A power station converts primary energy into electrical energy and delivers it to the grid. Its major **electrical** components are:

1. **Alternator (synchronous generator):** Converts mechanical energy from the turbine into 3-phase electrical energy, usually at 6.6–11 kV (up to 25 kV in large plants).
2. **Excitation system:** Supplies DC to the rotor field (static or brushless exciter) and, with the **AVR**, controls the terminal voltage and reactive power.
3. **Governor (control):** Adjusts the turbine input to hold speed/frequency and share active power.
4. **Generator step-up transformer:** Raises the voltage from generator level to transmission level (e.g. 11/132 kV).
5. **Busbars:** Conductors that collect power from generators and distribute it to outgoing feeders.
6. **Switchgear:** Circuit breakers (SF₆/vacuum), isolators and earthing switches to connect, disconnect and protect equipment.
7. **Protective relays and instrument transformers:** CTs and PTs feed relays (differential, overcurrent, distance) and meters.
8. **Lightning arresters:** Protect equipment from lightning and switching surges.
9. **Station auxiliary transformer and auxiliaries:** Supply pumps, fans, lighting, cooling inside the plant.
10. **Control room, metering and SCADA:** Monitor and control the plant; energy meters record export.
11. **Battery bank and DC system:** Supplies relays and breaker trip coils even during AC failure.
12. **Earthing system:** Safe path for fault currents and personnel safety.

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

## Check yourself

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

1. What does the excitation system with AVR do?
   A. Supplies DC to the rotor field and controls terminal voltage and reactive power
   B. Controls speed
   C. Steps up the voltage
   D. Interrupts fault current
   Answer: A. The exciter gives rotor field current; the AVR adjusts it to hold voltage and reactive output. (Key point: Excitation and AVR)

2. What is the function of the governor?
   A. Regulates terminal voltage
   B. Adjusts turbine input to hold speed/frequency and share active power
   C. Protects against lightning
   D. Measures energy export
   Answer: B. The governor controls the mechanical input, hence frequency and active power. (Key point: Governor)

3. Why is a generator step-up transformer needed?
   A. To lower the voltage for auxiliaries
   B. To convert AC to DC
   C. Generator voltage (6.6-25 kV) is raised to transmission level, e.g. 11/132 kV
   D. To store energy
   Answer: C. Generators are limited in voltage, so the GT raises it for transmission. (Key point: Generator step-up transformer)

4. Why does a power station have a battery bank and DC system?
   A. To drive the turbine
   B. To excite the grid
   C. To supply consumers
   D. To power relays and breaker trip coils even during AC failure
   Answer: D. Protection and tripping must work when AC supply is lost. (Key point: Battery bank)

5. What do lightning arresters protect against?
   A. Lightning and switching surges
   B. Overload
   C. Low frequency
   D. Earth resistance
   Answer: A. Arresters divert surge overvoltages to earth to protect equipment. (Key point: Lightning arresters)

## Related in Power System Analysis I

- [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
- [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

## Related in other subjects

- [Civil, mechanical and electrical components](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Ahydropower-civil-mech-elec) — Power Plant Design, chapter 3
- [Annual working cost of power station (a, b, c)](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Apower-station-annual-cost-abc) — Utilization of Electrical Energy, chapter 6
- [Fire fighting system in power station](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Afire-fighting-power-station) — Power Plant Equipment, chapter 4, asked 5×
- [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