9 a]What is electric power supply system? Draw a single line diagram of a typical a.c power supply scheme.
Solution :
Electrical energy is generated at generating stations which are usually situated far away from the consumers. Hence an extensive network of conductors between generating stations and consumers is required. These networks of conductors are divided into two main components, called transmission and distribution system.
The generation, transmission and distribution system of electrical power is called Electrical power supply system.
The electrical power supply system consists of 3 divisions:
- Generation
- Transmission
- Distribution
The power is generated in generating station. The transmission system is to deliver bulk power from generating station to load centers and to large industrial consumers. The distribution system is to deliver from load centers to various consumers.
The block diagram and single line diagram is as shown in fig.
The electrical power generated by 3 phase alternators in generating stations.
Usually the generated voltage is 11KV in certain cases 33KV also.
In order to reduce the copper loss and for economy reasons the voltage is stepped up from 11KV to 220KV using step up transformers.
The Primary transmission lines transmit the power from generating station to primary substations.
At this primary substation the voltage is step down to 33KV by using step down transformer.
Then the secondary transmission lines transmit the power to various substations and to large Industries.
In primary distribution station the voltage is step down to 33KV to 11KV using step down Transformer.
These substations transmit the power to various areas and to the medium scale industries.
In each area using step down transformer the voltage is step down to 11KV to 415V
The most of domestic, commercial and small scale industries are supplied power at low voltage i,e 415V to 3 Phase load and 230V to single phase loads.
