Determination of instrument current transformer errors in frequency range up to 1 kHz

Abstract

Two procedures for determining instrument current transformer (ICT) errors in the specified frequency range are described in the paper. The basis is use of accurate, frequency independent resistors, the ratio of which corresponds to the ratio of measured currents. These resistors are included in the primary and secondary circuit of the measured ICT. The difference in voltage drops across them corresponds to the ratio error and their phase shift to the phase displacement. The evaluation of the real and imaginary component of this difference is performed using a lock-in amplifier, phase-locked at the voltage corresponding to the primary current. In the case of primary currents of 100 A to 1 000 A, the use of resistors in the primary circuit is difficult with respect to their power loss. The procedure using a current transducer is also described.