Using a Current Loop and Homogeneous Primary Winding for Calibrating a Current Transformer

This paper presents two methods for determining the ratio error and the phase displacement of a protective current transformer (PCT) with a transformation ratio of 10 kA/1 A and a measuring current transformer (MCT) with a transformation ratio of 20 kA/5 A. The primary conductor passed by a current (10 or 20 kA) placed in the center of the toroid is replaced by a current loop with ten turns placed in the center of the toroid. In the second case, the conductor is replaced by ten turns uniformly distributed along the circumference of the toroid. The primary current (2 or 1 kA) is measured in both cases using a toroidal current comparator, and the secondary current difference is evaluated by means of a current transformer (CT) error measurement system. The errors were also measured using a CT analyzer.