Backfeeding
Encyclopedia
Backfeeding occurs when electric power
flows in the opposite direction from its usual flow. An alternating current power station
typically delivers power to the power grid by inducing a current to flow into the power grid when the voltage is positive, and inducing it to flow out of the power grid when the voltage is negative, and a typical power grid load (e.g. factory or home) induces current to flow out of the power grid when the voltage is positive and into the power grid when the voltage is negative. If either of these types of facilities starts inducing current like the other, then backfeeding is occurring. A power station will typically backfeed when it is shut down, due to local loads (e.g. lights or repair equipment). A power grid load may backfeed if it has distributed generation
installed, such as a grid-connected photovoltaic solar power
system or a microturbine-based power generator. It is also possible for an electric motor to temporarily backfeed if it is mechanically overpowered (see regenerative braking).
For cost reasons, many of the circuit (overcurrent) protection and power quality control (voltage regulation) devices used by electric utility companies are designed with the assumption that power always flows in one direction. Setting up an interconnection agreement for equipment designed to backfeed between an electric utility customer with distributed generation and their power company can involve nontrivial engineering and possibly equipment upgrade costs to keep the distribution circuit properly protected. Such costs may be minimized by limiting distributed generation capacity to less than is locally consumed and guaranteeing this condition by installing a reverse-power relay that opens if backfeeding occurs.
Electric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...
flows in the opposite direction from its usual flow. An alternating current power station
Power station
A power station is an industrial facility for the generation of electric energy....
typically delivers power to the power grid by inducing a current to flow into the power grid when the voltage is positive, and inducing it to flow out of the power grid when the voltage is negative, and a typical power grid load (e.g. factory or home) induces current to flow out of the power grid when the voltage is positive and into the power grid when the voltage is negative. If either of these types of facilities starts inducing current like the other, then backfeeding is occurring. A power station will typically backfeed when it is shut down, due to local loads (e.g. lights or repair equipment). A power grid load may backfeed if it has distributed generation
Distributed generation
Distributed generation, also called on-site generation, dispersed generation, embedded generation, decentralized generation, decentralized energy or distributed energy, generates electricity from many small energy sources....
installed, such as a grid-connected photovoltaic solar power
Solar power
Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...
system or a microturbine-based power generator. It is also possible for an electric motor to temporarily backfeed if it is mechanically overpowered (see regenerative braking).
For cost reasons, many of the circuit (overcurrent) protection and power quality control (voltage regulation) devices used by electric utility companies are designed with the assumption that power always flows in one direction. Setting up an interconnection agreement for equipment designed to backfeed between an electric utility customer with distributed generation and their power company can involve nontrivial engineering and possibly equipment upgrade costs to keep the distribution circuit properly protected. Such costs may be minimized by limiting distributed generation capacity to less than is locally consumed and guaranteeing this condition by installing a reverse-power relay that opens if backfeeding occurs.