Electric power distribution
Electric power distribution is the final stage in the delivery of electricity. Electricity is carried from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmission voltage to medium voltage ranging between 2 kV and 33 kV with the use of transformers.[1] Primary distribution lines carry this medium voltage power to distribution transformers located near the customer's premises. Distribution transformers again lower the voltage to the utilization voltage used by lighting, industrial equipment and household appliances. Often several customers are supplied from one transformer through secondary distribution lines. Commercial and residential customers are connected to the secondary distribution lines through service drops. Customers demanding a much larger amount of power may be connected directly to the primary distribution level or the subtransmission level.[2]
The transition from transmission to distribution happens in a power substation, which has the following functions:[2]
Urban distribution is mainly underground, sometimes in common utility ducts. Rural distribution is mostly above ground with utility poles, and suburban distribution is a mix.[1]
Closer to the customer, a distribution transformer steps the primary distribution power down to a low-voltage secondary circuit, usually 120/240 V in the US for residential customers. The power comes to the customer via a service drop and an electricity meter. The final circuit in an urban system may be less than 15 metres (50 ft) but may be over 91 metres (300 ft) for a rural customer.[1]
Modern distribution systems[edit]
Traditionally, the distribution systems would only operate as simple distribution lines where the electricity from the transmission networks would be shared among the customers. Today's distribution systems are heavily integrated with renewable energy generations at the distribution level of the power systems by the means of distributed generation resources, such as solar energy and wind energy.[23] As a result, distribution systems are becoming more independent from the transmission networks day-by-day. Balancing the supply-demand relationship at these modern distribution networks (sometimes referred to as microgrids) is extremely challenging, and it requires the use of various technological and operational means to operate. Such tools include battery storage power station, data analytics, optimization tools, etc.