The key role of the electrical power distribution system in plants or buildings is to receive power at one or more points of supply and then transfer it to the different electrical loads such as electrical motors, lighting, and many other purposes.
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The radial distribution system is one of the easiest systems where separate feeders radiate from a single substation and feed the distributor at one end. It uses a single utility path source between the substation and the consumer. In this type of system arrangement, the electricity flow is in a single direction, and if it disrupted, the effect would be a total loss of power.
In term of equipment initial cost, they are least expensive. They are not highly reliable and can be commonly found in sparsely populated areas. However, the major constraint to this system is that it is only feasible where low voltage electricity is produced, and the substation is situated at the centre of the load. At feeder end, the distributor will be heavily loaded, and on the other hand, voltage fluctuation will occur.
Ring or loop distribution system: Ring or loop distribution system has more than one direction between the power source and consumer. As the name suggests, the connection will take the shape of a loop circuit (loop originate through the service area and return to the original point). They are mostly preferred because there is less voltage fluctuation at a consumer terminal.
The big advantage of this system is that switches are thrown automatically or manually if power failure from one source and power from the second source is provided to the consumers. They are more reliable as two feeders are fed to each distribution transformer. That means the continuity of power supply from the alternative route is ensured in case of power failure in any feeder section. However, they are expensive than the radial system as it needs more conductors and switches.
Interconnected distribution system: If two or more substations or generating stations energize the main ring feeder, it is considered an interconnected distribution system. They are more complex and interlocking with the loop system. Such a system guarantees reliability in case of power failure. In peak hour demand any area can be fed from two, three, four or more different power supplies to meet the energy demand, resulting from the increased load.
The quality service of interconnected system is very much high but are more expensive. Therefore, they are mostly found in heavily populated areas and high density urban or downtown regions.