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CONNECTION SCHEMES OF DISTRIBUTION SYSTEM

                        CONNECTION SCHEMES
                                            OF 
                        DISTRIBUTION SYSTEM:

CONNECTION SCHEMES OF DISTRIBUTION SYSTEM :
                                          All distribution of electrical energy is done by constant voltage system. In practice the following distribution circuits are generally used.

RADIAL SYSTEM :

                                          fig 1.1

                   In this system separate feeders radiate from a single Bub station and teed the distributors at one end only. Fig.1.1. shows a single line diagram of a radial system for A.C distribution. The radial system is employed only when power is generated at low yoltage and the sub station is located at the centre of the load. 

Advantages :
                       1. Simplest distribution circuit 
                       2. Lowest initial cost 

Disadvantages :
                       1. The end of the distributor nearest to the feeder will be heavily loaded. 
                       2. The consumers depend upon a single feeder and single distributor, any fault on the feeder or distributor cuts off supply to the consumers. 
                       3. The consumers at the distant end of the distributor would be subjected to serious voltage fluctuations.

RING MAIN SYSTEM :

In this system, the primaries of distribution transformers form a loop. The loop circuit starts from the sub station bus bars, makes a loop through the area to be served and returned to the sub station, Fig 12.9. shows single line diagram of ring main system for A.C distribution. The sub station supplies power to the closed feeder LMNOPQRS. The distributions are tapped from different points M, O and Q of the feeder through distribution transformers. 

Advantages :
                      1. Less voltage fluctuations at consumer terminals. 
                      2. The system is more reliable because each distributor is fed by two feeders. In the event of fault on any section of the feeder the continuity of supply is maintained.

INTERCONNECTED SYSTEM :

                                               fig 13.8

When the feeder ring connected by two or more generating stations or sub stations is called inter connected system fig. 13.8 shows the single line diagram of inter connected system. The closed feeder ring ABCD as shown in fig.13.8 is supplied by two sub stations S, and S, at points D and C respectively. Distributors are connected to points O, P, Q and R of the feeder ring through distribution transformers. 

Advantages :
                      1. The service reliability is increased 
                      2. Any area fed from one generating station during peak load hour can be fed from the other generating station. Hence efficiency of the system is increased)

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