The Trivector meter is a measuring instrument which measures the kW, kVAr, the kVA of a power line. These instruments can measure both power as well as energy. Trivector meters are normally used in substations and to measure the power flowing through the feeders. They are used for billing power drawn by industrial customers. The Trivector enables the simultaneous measurement of different electrical parameters which enables accurate assessment of the power consumed.

Trivector is called so as it measures three vectors representing the active, reactive and apparent power of a line. Trivector meters come in two quadrant and four quadrant models. The four quadrant model can measure both the incoming (import) and the outgoing power (export) while the two quandrant trivector meter can measure either imported or exported power.

In earlier days, the Electromechanical trivector meters were used. Today, though, almost all Trivector meters are of the static type. Modern Trivector meters can measure many parameters apart from the active, reactive and apparent power.