# Definition: Reactive Power

From Open Energy Information

# Reactive Power

The portion of electricity that establishes and sustains the electric and magnetic fields of alternating-current equipment. Reactive power must be supplied to most types of magnetic equipment, such as motors and transformers. It also must supply the reactive losses on transmission facilities. Reactive power is provided by generators, synchronous condensers, or electrostatic equipment such as capacitors and directly influences electric system voltage. It is usually expressed in kilovars (kvar) or megavars (Mvar).^{[1]}

### Wikipedia Definition

- In electric power transmission and distribution, volt-ampere reactive (var) is a unit by which reactive power is expressed in an AC electric power system. Reactive power exists in an AC circuit when the current and voltage are not in phase. The correct symbol is var and not Var, VAr, or VAR, but all three terms are widely used, and VAR is widely used throughout the power industry infrastructure. The term var was proposed by the Romanian electrical engineer Constantin Budeanu and introduced in 1930 by the IEC in Stockholm, which has adopted it as the unit for reactive power.Vars may be considered as either the imaginary part of apparent power, or the power flowing into a reactive load, where voltage and current are specified in volts and amperes. The two definitions are equivalent.The unit "var" does not follow the recommended practice of the International System of Units, because the quantity the unit var represents is power, and SI practice is not to include information about the type of power being measured in the unit name., In electric power transmission and distribution, volt-ampere reactive (var) is a unit by which reactive power is expressed in an AC electric power system. Reactive power exists in an AC circuit when the current and voltage are not in phase. Per EU directive 80/181/EEC (the "metric directive"), the correct symbol is lower-case "var", although the spellings "Var" and "VAr" are commonly seen, and "VAR" is widely used throughout the power industry. The term var was proposed by the Romanian electrical engineer Constantin Budeanu and introduced in 1930 by the IEC in Stockholm, which has adopted it as the unit for reactive power.Special instruments called varmeters are available to measure the reactive power in a circuit.Vars may be considered as either the imaginary part of apparent power or the power flowing into a reactive load, where voltage and current are specified in volts and amperes. The two definitions are equivalent.The unit "var" does not follow the recommended practice of the International System of Units (SI) because the unit var is representative of a form of power, and SI practice is not to include information about the type of power being measured in the unit name. The SI unit of power is the watt, which is numerically equivalent to the var.

- Also Known As
- volt-ampere reactive (var)

- Related Terms
- transmission lines, electricity generation, transformer, system, power, smart grid

##### References

AnGlossary Definition