Main results of supplementary comparisons of high voltage and current measuring systems

High voltages of alternative current (AC) are important because they are needed for numerous applications in physics and engineering. High AC voltages are also used to test insulating materials for their dielectric properties. Calibrations of instruments for high-voltage measurements should provide metrological traceability to national standards. This applies to the requirements for both voltage measuring instruments and current measuring instruments. The transformer for high-voltage measurements is used to reduce the values of currents and voltages during measurements in high-voltage electrical networks. Voltage transformers (VTs) are used to accurately measure high AC voltages. Current transformers (CTs) are used to convert line currents in power systems to levels that are acceptable for other measuring instruments, which are necessary to trip protective devices. There are measuring installations that are well known for accurate measurements of the CT coefficient for large primary currents, and systems for determining the behaviour of the industrial current and VT under distorted waveforms, etc. The calibration of a high voltage measuring system must be traceable to national or international measurement standards. Mutual comparisons of calibration results of CT and VT standards are carried out with the participation of several national laboratories. The results of high voltage transformer measuring systems (GULFMET.EM-S6) and high current transformer measuring systems (GULFMET.EM-S7) supplementary comparisons are described. The comparisons were carried out between national laboratories from three Regional Metrology Organizations. In general, the participants of both comparisons have demonstrated a good agreement of the results in the ratio error and phase displacement for high voltage and current. The comparison results may be used to improve the participants’ existing calibration and measurement capabilities entries in the Key Comparison Database (KCDB) of the International Bureau of Weights and Measures  (BIPM).