Compensation of nonlinearities in a current transformer for the reconstruction of the primary current

The measurement of the current in industrial electrical devices is often carried out by current transformers. The reliability of these devices is compromised when the measured current is higher than the nominal value, due to the saturation and hysteresis effects of the magnetic core. In this paper, a nonlinear model of the current transformer is identified by means of a separable least squares technique. This model is successfully employed for the estimation of the primary current starting from experimental measurements of the distorted secondary current. In this way, a fair estimate of the primary current is obtained even when its maximum intensity reaches up to 60 times (or more) its nominal value. Some sensible experimental trials are reported in order to demonstrate the effectiveness of the technique developed.