Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

active power

See real power
active power line conditioner

a device which senses disturbances on a power line and injects compensating voltages or currents to restore the line's proper waveform.

reactive power Q
The region of allowable operation is determined by factors such as rotor thermal limit, stator thermal limit, rated power of prime mover (alternator operation), and stability torque limit.
reactive power
(1) electrical energy per unit time that is alternately stored, then released. For example, reactive power is associated with a capacitor charging and discharging as it operates on an AC system. Symbolized by Q, with units of volt-amperes reactive (VAR), it is the imaginary part of the complex power.

(2) the power consumed by the reactive part of the load impedance, calculated by multiplying the line current by the voltage across the reactive portion of the load. The units are vars (volt-ampere reactive) or kilovars.