In the transient process of power grid faults

the transferring distortion of current transformer (CT) can seriously affect relay protection performance. Under these conditions

it is difficult to analyze the ferromagnetic characteristic of the magnetizing branch in the transient equivalent circuit of CT. The Jiles-Atherton hysteresis model (J-A model)

which is widely used in digital simulations

can accurately describe the hysteresis and saturation process of the core characteristics; however

to acquire the parameters of the J-A model of current transformers in practical use is still a challenging problem. In this paper

physical tests based on a practical CT and parameter identification are presented to solve the problem. The basic hysteresis loops of P

PR

and TPY class of practical current transformers are obtained through physical tests. Thus

the J-A model parameters are identified using a hybrid genetic/simulated annealing algorithm

based on which transient simulation models of different class CTs are constructed. The effectiveness of the proposed method is verified via dynamic physical simulation tests. A typical accident is analyzed based on these models.