Reactive power measurement in Balanced Three phase circuit

Measurement of Reactive Volt- AMPERES

For the measurement of reactive power in a single-phase circuit we used compensated wattmeter. In compensated wattmeter the voltage applied to the pressure coil is 90° out of phase with the actual voltage and the wattmeter will read the reactive power  VI cos(9 – Φ) i.e VI sinΦ.In single-phase measurement the filed of pressure coil lag behind by 90° when it measures actual power.

Single wattmeter method is used for power measurement in balanced three-phase circuit. The current coil of the wattmeter is inserted in one line and the pressure coil of it is connected across the other two lines.


   Reactive Power Measurement in Balanced Three-Phase Circuit
                 Phasor Diagram


The current flowing through the current coil of wattmeter is

I2=Ip (say)

The potential difference(pd) across the potential coil of wattmeter

Wattmeter indicates:

Reactive power can also be determined from two wattmeter readings connected for measurement of power

Reactive power of load circuit, Q

Related terms:

  1. Measurement of Three Phase power:Three wattmeter method
  2. Two Wattmeter Method of Power Measurement
  3. Power factor
  4. Star and Delta connection

For more related terms in Electrical Engineering


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