Virtual Instrument for Testing of Current and Voltage Transformers

Instrument transformers, namely, current and voltage (potential) transformers are characterized by their ratio and phase errors. A novel virtual instrument that determines the errors of an instrument transformer using a quasi-balance technique is proposed in this paper. Operating on the secondary quantities of the test and standard transformers, two independent quasi-balance conditions are obtained. The errors of the test transformer are then determined using the two quasi-balance settings alone. The method inherently possesses all the advantages of an ac bridge but dispenses with the tedious iterative balancing. A prototype unit built and tested establishes the practical viability of the proposed technique