Distributions systems represent an important parts in the electrical grids and for this reasons the electrical generation & distribution companies delicate approximately 40% of the capital investment for distribution systems while the remaining is given to generation and transmission (40% generation & 20% transmission).
The power distribution system is particularly important for an electrical utility for two reasons:
- It is close part to the Customers and any failure in distribution system affect the customer directly. For example failures in transmission and generation sections may not cause customer service interruptions.
- It’s high investment cost.
Components Of power Distribution System
According to figure given below which represents single line diagram of typical electrical power system network the main components of a power distribution system are:
- Sub transmission system: The sub-transmission system is part responsible for transmission the electrical power from the transmission substation (the source of bulk power) into distribution substation. The transmission voltage lays in the range 12.47- 275 kv.
- Distribution substation: It always steps down the sub-transmission voltage to level suitable for the primary feeders (220/33kv, 100/11kv).
- Primary feeders: The primary feeders distribute the power from the low bus side of distribution substation into distribution transformer located in load centers. The nominal voltage of this feeders lay in the range 3.3 to 33 kv.
- Distribution transformers: Distribution transformer usually connected to the primary feeders, they reduce the distribution voltage to the utilization voltage. Distribution transformer are rated from 10 to 500 KVA with voltages 3300/415, 11000/415 volts.
- Secondary feeders : Distribute the power from the secondary side of the distribution transformer into customers services with 415 volt.