Power system distribution involves delivering electrical energy from power plants to consumers through a network of transmission and distribution systems. The process begins at power plants, where energy from coal, gas, nuclear, water, and wind is converted into electrical energy. These plants use three-phase generators, typically rated between 50 to 1300 MVA, with terminal voltages ranging from a few kV to 20 kV, depending on the size and age of the units.
The transmission system is designed to reduce energy losses by using high voltages. Generator step-up transformers at power plant substations increase the voltage and decrease the current for efficient long-distance transmission. The transmission system has three main functions: delivering energy from generators to the system, providing for energy interchange among utilities, and supplying energy to subtransmission and distribution systems.
The subtransmission system consists of step-down transformers and lines that connect bulk power substations to distribution substations. These transformers step down high transmission voltages to levels suitable for distribution, often supplying large industrial loads or specific regions.
The distribution system includes distribution substations, which decrease the subtransmission voltages to primary distribution levels. These substations also protect the system with circuit breakers and surge arresters. Feeders distribute electricity to several three-phase sections connected through various protective devices.
The distribution network has two main parts: primary and secondary distribution. Primary distribution transfers electricity from substations to distribution transformers, stepping down the voltage to secondary levels. Secondary distribution connects to customer premises via service conductors, providing power for residential, commercial, and light industrial use. Service conductors connect through meters for billing and planning and to service panels on customer premises, which contain circuit breakers or fuses that supply power to various devices.
An electric power system consists of power plants, generators, transformers, and substations.
Power plants convert various forms of energy into electric energy, with three-phase generators.
The step-up transformers increase voltage and decrease current to reduce transmission losses.
The transmission system, a network of three-phase lines and substations, delivers energy to sub-transmission and distribution systems.
The sub-transmission system uses step-down transformers, substations, and lines to connect bulk power substations to distribution substations.
Distribution substations contain step-down transformers that lower sub-transmission voltages to primary distribution levels for local distribution.
Primary distribution feeders are divided into several three-phase sections, sometimes with single-phase laterals connected via fuses.
Feeders and laterals, whether overhead or underground, run along streets to supply distribution transformers, which further reduce voltage to secondary levels.
These transformers, installed on poles, pads, or in vaults, channel energy through secondary mains and service conductors to customer loads.
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