Block Diagram of AC power supply
The standard voltages which are used for the generation, transmission and distribution of electrical energy in our country are as follows:
i. Generation: 6.6 KV, 11 KV, 33 KV (of which 11 KV voltage generation is widely used). Practically 13.2 KV to 13.8 kV is used normally.
ii. Transmission: 33 KV, 66 KV, 132 KV, 220 KV and 400 KV (380 KV).
iii. Distribution: There are two types of distribution:
a. AC: 415V/240 V
b. DC: 250V/500 V
The electrical power is generated in different power stations situated at different places and this power is transmitted to different load centres. The power stations may be hydel, thermal or atomic. The thermal power stations met up the major portion of load requirements and used the steam turbine as a prime mover. The hydel power stations use the prime movers in form of water turbines. The atomic or nuclear power stations using also steam turbines as prime movers.
In a steam power station, pulverised coal is fired in the combustion chamber of the boiler which will convert boiler feed water into steam. This steam will impinge on the runner of the steam turbine & producing shaft energy. The turbine & the alternator are mechanically coupled. The shaft energy of the turbine produces electrical power in the alternator at standard voltage. This electrical power is being transferred to the switching yard of the power station for transmission purposes.