Another system of distribution which eliminates the disadvantages of the radial system is used in practice called ring main distribution system.
In such system, the feeders covers the whole area of supply in the ring fashion and finally terminates at the substation from where it is started. The feeder is in closed loop from and looks like a ring hence the name given to the system as ring main system. This is shown in the Fig. 1.
The feeder in the ring fashion is divided into number of sections as AB, BC, CD, DE and EA. The various distributors are connected at A, B, C, D and E. Each distributor is supplied by the two feeders and hence the design is similar to the two feeders in parallel on different paths. Hence if there is any fault on any part of the feeder, still the consumers will keep on getting the continuous supply. For example, if the fault occurs at point P in the section AB of the feeder can be isolated and repaired. The feeder can be fed at one or more feeding points. Thus the disadvantages of radial system are eliminated in this system. The great saving in copper is another major advantage of the ring main system.
Drawback of Radial power distribution system:
ReplyDelete1. In case of any feeder fail, the associated substations would not get power as there was no alternative path to feeder to the effected substation.
2. If the feeder is long, there is voltage drop problem at the far way substations.
Benefit of Ring Main power distribution system:
1. In this system, power sources and sub-stations are interconnected alternate routes, thus forming a closed ring. In case of fault or damage to any section of the ring, that section may be disconnected for repairs and power will be supplied from both ends of the ring.
2. There is no voltage drop problem as the power interconnected from alternate routes.
Magnitude of Fault Current is high, in a ring main feeder than a redial?
Magnitudes of fault current depend on:
i. Capacity of power source
ii. Line impedance.
iii. Type of fault.