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. 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.
A 50 kVA pole-mounted distribution transformer
Substation near Yellowknife, in the Northwest Territories, Canada
High voltage power pole in rural Butte County, California
Electric power transmission
Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines that facilitate this movement form a transmission network. This is distinct from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution. The combined transmission and distribution network is part of electricity delivery, known as the electrical grid.
A four-circuit, two-voltage power transmission line; Bundled 2-ways
A typical ACSR. The conductor consists of seven strands of steel surrounded by four layers of aluminium.
Three abreast electrical pylons in Webster, Texas
New York City streets in 1890. Besides telegraph lines, multiple electric lines were required for each class of device requiring different voltages.