•Before we study Fault and Fault Currents, we need to have an idea about the power distribution system as it has some connection to power system protection schemes.
•When a consumer requests electrical power from a supply authority, ideally all that is required is a cable and a transformer, shown physically as follows:
Figure 1: A Simple Distribution System
The distributions system shown in figure-1 is called a RADIAL system and can be shown schematically in the following manner:
Figure -2: A Radial Distribution System
•Advantages: If a fault occurs at T2 then only the protection on one leg is called into operation. The other consumers are not affected.
•Disadvantages: If the conductor to T2 fails, then supply to this particular consumer is lost completely.
•This disadvantage of the distribution system shown in figure-2 can be overcome by introducing parallel feeders; however, this uses more copper and is not always the most economic:
Figure – 3: A Parallel Distribution System
The RING MAIN system, shown in figure-4, is the most favoured distribution system.
Figure – 4: A Ring Main Distribution System
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