Oskars Petersons

Oskars Petersons worked on electrical metrology at the National Institute of Standards and Technology. With John D. Ramboz, Petersons coauthored the 1991 report describing NIST's laboratory current transformer calibration service. The report treats current ratio and current-transformer phase displacement as distinct measurement results.^[ref]

A current transformer allows a secondary electric current to represent a larger or smaller primary current. Its marked ratio is a nominal conversion, whereas the measured ratio can differ. The report expresses the measured ratio as the marked ratio multiplied by the current-transformer ratio correction factor, and uses a secondary-leading sign convention for the reported phase displacement.^[ref]

An original calculation illustrates the distinction. A marked ratio of $200$ A:$5$ A gives $K_n=40$. If the current-transformer ratio correction factor is $1.0002$, the measured magnitude ratio is $K=40.008$. A secondary reading of 5 A then represents 200.04 A under those stated conditions, rather than exactly 200 A.

Magnitude alone is not a full alternating-current description. If the secondary phasor leads the primary by $\beta$ and their magnitude ratio is $K$, a consistent convention isThe magnitude correction and phase rotation address different errors. A measurement system can reproduce one accurately while requiring correction of the other. The joint report's calibration circuits, including compensated current comparators, give these distinctions an apparatus-level setting rather than leaving them as ideal-transformer identities.^[ref]