An Improved Frequency-Compensated Capacitance Bridge for Accurate Shunt Reactor Loss Measurements at Very Low Power Factors

An improved compensating current circuit for making the current-comparator-based capacitance bridge insensitive to frequency fluctuations when used for measuring shunt reactor loss is described. An estimated accuracy of 1 percent can be achieved for loss measurements of shunt reactors operating at power factors as low as 0.001. There are no phase adjustments in the circuit, only gain (or magnitude). Most of the errors introduced by the circuit are, therefore, confined to the inductive balance of the bridge which has a much larger error budget than that of the loss tangent. The loss tangent balance is affected by errors of the second order only.