Identification of a grey-box model of nonlinear current transformers for simulation purposes

Current Transformers (CTs), which are often used as current sensors, show highly nonlinear behavior when their input current is large w.r.t. its nominal value. In many safety-related applications, (e.g._ in the field of electrical protection) neglecting such a nonlinear behavior may lead to dangerous situations if the overall system is designed with the assumption of ideal'' sensors. A reliable dynamic model of the CT is then necessary to design the application suitably. In this paper, a procedure is proposed to identify a nonlinear dynamic model for a CT directly from real data, with almost no need for a priori information on the physical parameters characterizing either the CT or the electrical circuit in which the CT is inserted ("grey-box" approach). The model is obtained such that it is suitable for effective, low-computational burden simulations. The identification procedure is validated by comparing simulated and real data. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.