F. Castelli, M. Faifer
The Instrument Transformer Bridges for Testing and Characterizing, for Harmonic Measurements, Instrument Transformers
The modern development of electric power systems is increasingly demanding for high improvements in the accuracy of metering and testing methods in both HV and high current, namely, in testing the instrument transformers. The necessity of determining if the existing instrument transformers are usable for harmonic measurements is, at present, also required. The illustrated Instrument transformer bridges implement the, at present, used ratio transformer bridge to testing the instrument transformers and their usability for harmonic measurements. The illustrated bridges uses two ratio transformers, an instrument transformer and a decade ratio transformer. The use of the instrument transformer allows to supply the reference standard ( S ) at its secondary low rating and extends the bridges' range without extending the dynamic range of both S and decade ratio transformer. Thus the illustrated bridges undeniably appears innovative of the, at present, used ratio transformer bridge technique that in the illustrated form could find wider use. The uncertainty of 0.5 ppm, of the used ratio transformer has been achieved in the absolute and relative test of both voltage and current transformers by experimental bridges.
