AC Distribution system


In this article we are discuss about the A.C distribution system which means how to A.C power distribute. In this system we will also  describe about the type of AC distribution system .

A.C Distribution system


  1.  Primary distribution system


                 It is the main type of  A.C distribution system

·       It is that part of AC distribution system which operate at voltage such as 3.3KV,6.6KV and 11kv . which is higher than that of general utility 230/440v and handle large blocks of power from the generating station located in or near the city.
At these substation which is known as secondary substation ,the voltage is step down to 11,6.6,3.3kv with the help of power transformer for primary distribution .the feeder may be radial ,parallel , interconnected or ring type .

A.    Radial feeder

AC distribution system, types of feeder, radial feeder
 the feeder radiates from  the secondary substation and branches into sub feeders and laterals which extend the distribution transformer are connected to the primary feeders,sub-feeders and laterals usually through the fuse cut out ,it is the simplest,most economical and most commonly used.it is advantages for supplying the power to heavy industrial load and near the
secondary substation ,isolated load such as villages. But there are some draw-back also-

·       Poor reliability

When a foult occurs at any point on the feeder,supply to all consumers beyond that foult point towords the tell end get interrupted.

·       In case of increase in load demand ,the length of the feeder has to be extended and may result in a greater voltage drop.

B.    Parallel feeders:
AC distribution system, types of feeder, radial feeder, ring main feeder

In a parallel feeders system ,two radial feeders feed from the same or different secondary substation are run in parallel each feeder,though capable of supplying the entire load,shares the total load equally in normal condition. This system is expensive but reliability is increased as in case of fault on one feeder the total load can be supply by the healthy feeder . interruption of supply is only for the time duration that is taken in transferring the load from the faulty feeder to healthy one either by manual or automatic cities.Such a system is employed where ever the continuity of supplying is of greater importance

Loop feeder:


In a loop feeder system two or more radial feeder connected from the same or different secondary substations are setup on different roots of load areas.
AC distribution system, types of feeder, radial feeder
THE arrangement having the end of two feeder tied together through the normally open switching device is known as open loop system.while the arrangement having the ends of two feeders tied together through the normally closed switching device known as ring man feeder  the use of  this system is restricted due to the very large investment . it is used where continuity of supply is first priority feeders end loop component must have sufficient reserve capacity to handle the load that may be transferred lender abnormal condition .

Interconnected N/W system
AC distribution system, types of feeder, radial feeder

In interconnected N/W system is very useful for AC distribution system .
When the feeder ring main is energized from two or more generating stations or substations,such systems known as interconnected n/w system. Because of interconnected feeder,power can be supplied to all the distributor transformer even though a part of network may be out of service. Such a system provides better reliability metro pollution cities where continuity of supply is the most important.

2.  Secondary distribution system


It is the second type of AC distribution system .
A.    Three phase 4 wire distribution system
B.    Single phase ,2 wire distribution system


The secondary distribution system may be  radial,open loop or N/W distributor. 
hence these are main type of C distribution system.

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