Major components of a power station and functions

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.

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