A Novel Transient Differential Protection Based on Projection Transform Model

A novel transient differential protection based on approximation and z-transform theorems is proposed in this paper. The differential function relates to time is firstly approximated to convolution of the projection of differential operator and the function itself, subsequently the digital equation of transmission line is established. The z-transform is employed to obtain the solution of the sampling equation, by which the propagation function and surge impedance in z domain are obtained. The impulse response of propagation function and surge impedance are solved by the zero-pole estimation method, therefore the simplified differential protection for distributed parameter line has been established. The EMTP simulations associated to a typical transmission system show that the algorithm is right and accuracy.