We should measure the losses of a shunt reactor at rated voltage and frequency. But for very high voltage shunt reactor, it may be difficult to arrange such a high test voltage during measurement of losses. This difficulty can be overcome, by measuring the losses of the shunt reactor at any voltage lower than the system voltage of the reactor. Then this measured loss is multiplied by the square of the ratio of rated current to the current of the reactor at applied reduced test voltage to obtain the loss at rated voltage.
As the power factor of the shunt reactor is very low, loss measurement of shunt reactor by conventional wattmeter is not very reliable, instead of bridge method of measurement may be adopted for better accuracy.
This test can not segregate the losses in various parts of the reactor. To avoid, correction of test result for a reference temperature, it is preferable to take the measurement when the average temperature of the winding becomes equal to the reference temperature.