The necessary requirements of a good distribution system are,
1. The continuity in the power supply must be ensured. Thus system should be reliable.
2. The specified consumer voltage must not vary more than the prescribed limits. As per Indian Electricity Rules, the variation must not be beyond ± 5 % of the specified voltage.
3. The efficiency of the lines must be as high as possible.
4. The system should be safe from consumer point of view. There should no be leakage.
5. The lines should not be overloaded.
6. The layout should not affect the appearance of the site or locality.
7. The system should be economical.
Though the a.c. transmission and distribution is used, still for certain applications such as d.c. motors, electrochemical work, batteries, electric traction etc. the d.c. supply is must. Hence along with a.c., d.c. distribution is also equally important. In a d.c. distribution, d.c. generators are used in the generating stations or a.c. is converted to d.c. using the converters like mercury are rectifiers, rotary converters etc. at the substations. Then the d.c. supply is distributed to the consumers as per the requirement.