The substation is electrical supply system which transfer the high voltage from the generating substation to the local distribution network.

1. Typical radial substation

In the radial substation there is only one source of feeding the load as shown in figure below. These supply system is unreliable because of total blackout when source fail.or line develop a fault. Such type of substation used in distribution system particularly in the rural area because of their unimportance.

2. Trapped substation

This supply is equally unreliable and insecure because there shall be totally supply failure when source or line become faulty.

3. LILO (Line In Line Out)

In these substation a long distribution line is brought in and brought out from newly created substation as show below. These scheme is bit expensive because of the need of an extra layout. But it is more secure.

4. Interconnected substation

This is the most preferred supply system which is safe secured and reliable . the outage of source and line does not effect power supply system because many other alternative are available.