Radial, Parallel, Ring main and Interconnected Distribution Systems
An electric power distribution system can be classified according to its feeder connection schemes or topologies as follows -
[Also read: Classification of distribution systems according to number of phases and wires involved.]
Although this system is simplest and least expensive, it is not highly reliable. A major drawback of a radial distribution system is, a fault in the feeder will result in supply failure to associated consumers as there won't be any alternative feeder to feed distributors.
Ring main distribution system is the most preferred due to its following advantages.
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- Radial distribution system
- Parallel feeders distribution
- Ring main distribution system
- Interconnected distribution
[Also read: Classification of distribution systems according to number of phases and wires involved.]
Radial distribution system
This system is used only when substation or generating station is located at the center of the consumers. In this system, different feeders radiate from a substation or a generating station and feed the distributors at one end. Thus, the main characteristic of a radial distribution system is that the power flow is in only one direction. Single line diagram of a typical radial distribution system is as shown in the figure below. It is the simplest system and has the lowest initial cost. |
| Image credit: Wikimedia commons |
Parallel feeders distribution system
The above-mentioned disadvantage of a radial system can be minimized by introducing parallel feeders. The initial cost of this system is much more as the number of feeders is doubled. Such system may be used where reliability of the supply is important or for load sharing where the load is higher. (Reference: EEP - Distribution Feeder Systems)
Ring main distribution system
A similar level of system reliability to that of the parallel feeders can be achieved by using ring distribution system. Here, each distribution transformer is fed with two feeders but in different paths. The feeders in this system form a loop which starts from the substation bus-bars, runs through the load area feeding distribution transformers and returns to the substation bus-bars. The following figure shows a typical single line diagram of a ring main distribution system.
Advantages of ring main distribution system
- There are fewer voltage fluctuations at consumer's terminal.
- The system is very reliable as each distribution transformer is fed with two feeders. That means, in the event of a fault in any section of the feeder, the continuity of the supply is ensured from the alternative path.