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
Dr. Madhu Mohan N., George, B., and Kumar, V. J., “Virtual Instrument for Testing of Current and Voltage Transformers”, in Instrumentation and Measurement Technology Conference, 2006. IMTC 2006. Proceedings of the IEEE, 2006.