Common distribution arrangements

Radial system

This is the simplest distribution circuit and has the lowest initial cost. In this system, separate feeders radiate from a single substation and feed the distributors at one end only.. The radial system is employed at low voltage and the substation is located at the center of the load.However, it suffers from the following drawbacks.

1. The end of the distributor nearest to the feeding point will be heavily loaded.

2. The consumers are dependent on a single feeder and single distributor.
   Therefore, any fault on the feeder or distributor cuts off supply to the consumers who are on the side of the fault away from the substation.

3. The consumers at the distant end of the distributor would be subjected to serious voltage fluctuations when the load on the distributor changes.

Due to these limitations, this system is used for short distances only. The radial system can be extended by introducing more laterals and sub-laterals.

Ring system

In this system, the primaries of distribution transformers form a loop. The loop circuit starts from the substation bus-bars, makes a loop through the area to be served, and returns to the substation.

The ring main system has the following advantages:

1. There are less voltage fluctuations at consumer’s terminals.

2. The system is very reliable as each distributor is fed via two feeders. In the event of fault on any section of the feeder, the continuity of supply is maintained.For example, suppose that fault occurs at any section of the feeder. Then the faulted section the feeder can be isolated for repairs and at the same time continuity of supply is maintained to all the consumers via the other feeder

Interconnected system

When the feeder ring is energized by two or more than two source, it is called interconnected system.

The interconnected system has the following advantages:

1. It increases the service reliability.

2. Any area fed from one generating station during peak load hours can be fed from the other generating station. This reduces reserve power capacity and increases efficiency of the system.