- At present, electrical power demand is rapidly increasing. For fulfilling the immense power demand; themodern time need creation of huge power generating stations. The power generating stations might be hydro – atomic, thermal or electric. Depending upon the resource availability, stations are constructed varied places. These places might not be nearer to load centers where the power is fully used. Hence it is essential to broadcast these power blocks from generating station to their load centers.
- Long and high voltage transmission networks are required for this purpose. Power is moderately generated in low voltage level. It is reasonable to transmit power at high voltage level. Electrical power distribution is done at lower voltage levels as specified by customers.For maintaining these voltage levels and for providing greater stability a number of transformation and switching stations have to be created in between generating station and consumer ends. These transformation and switching stations are generally known as Electric Substations. As per the purposes, the substations might be classified as:
- · Step Up Substation
Step up substations are directly related with generating stations. Generation of power is restricted to low voltage levels because of the limitations of the rotating alternators. These generating voltages should be stepped up for transmission of power over long distance. Thus there should be step up substation linked with generating station.
- · Step Down Substation
The stepped up voltages should be stepped down to different voltage levels at load centers for various purposes. As per the purposes; the step down substation are categorized in several subcategories.
- · Primary Step Down Substation
The primary step down substations are formed near to the load center with the primary transmission lines. Primary transmission voltages are stepped down to varied other voltages for secondary transmission purpose.
- · Secondary Step Down Substation
At load center, beside the secondary transmission lines, the secondary transmission voltages are stepped down for primary distribution use. The stepping down of secondary transmission voltages to primary distribution levels are rendered at secondary step down substation.
- · Distribution Substation
Distribution Substation is located where primary distribution voltages are stepped down to deliver voltages for feeding the actual customers through distribution network.
- · Bulk Supply or Industrial Substation
Bulk supply or industrial substation is generally a distribution substation although they are dedicated for one customer only. An industrial end user of large or medium supply group might be designated as bulk supply user. Individual step down substation is devoted to these end users.