Classification of Distribution System

Classification of Distribution System

The power system network is divided into three parts; Generation, Transmission, and Distribution. The power generated from the power plant is supplied to the load via transmission and distribution system.

In this article, we will explain the different types of distribution network. according to the shape of the system, the distribution network is classified into three types.

  • Radial Distribution System
  • Ring or Loop Distribution System
  • Grid or Interconnected Distribution System

Radial Distribution System

In this system, separate feeders radiate from a single substation and feed the distributor at one end only.

Below figure-1 shows a single line diagram of the radial system for the DC distribution system, where a feeder OC supplies a distributor AB at point A. Figure-2 shows a single line diagram of a radial system for AC Distribution.

In a radial system, only one path is connected between each consumer and the substation. The electrical power flows from the substation to the consumer along a single path.

Thus, if a fault occurs in the system, it results in a complete loss of power to the consumer.The initial cost of this system is low compared to other systems.

Simple in planning, design, and operation. The reliability of the radial distribution system is less. The distributor nearer to the feeding end is heavily loaded. Consumers at the far end would be subjected to voltage fluctuations with variations in load.


Ring or Loop Distribution System

The loop circuit starts from the substation bus-bars, makes a loop through the area to be served, and returns to the substation.

Figure shows the single line diagram of the ring main network for AC distribution where substation supplies to the closed feeder LMNOPQRS.

The distributors are tapped from different points M, O, and Q of the feeder through distribution transformers.

It is selected to carry its normal load plus the load of the other half of the loop also. The size of the feeder conductor in a loop distribution network is the same throughout the loop.

Less conductor material is required as each part of the ring carries less current in the radial system.
Fewer voltage fluctuations It is more reliable. It is difficult to design when compared to the designing of a radial system.


Grid or Interconnected Distribution System

When the feeder ring is energized by two or more than two generating stations or substations, it is called an interconnected system.

Below figure shows the single line diagram of the interconnected system where the feeder ring ABCD is supplied by two substations S1 and S2 at points D and C respectively.

Distributors are connected to points O, P, Q, and R of the ring through distribution transformers.
The reliability and quality of the service of the interconnected type distribution arrangement are much higher than the radial and loop arrangements.

It is more difficult to design and operate than radial or loop systems. It increases the reliability of supply. Losses are less and efficiency is more.

The quality of service is improved. The initial cost is more. Difficult in planning, design, and operation.


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