Research On Transient Simulation Of Current Transformer

Current transformer (CT) plays a very important role in power system. As the primary time constant is big in the extra high voltage system, when the short-circuit fault happens, the direct short-circuit current decays slowly, so that the P class CT is too easy to be saturation to transmit the primary signal exactly. It possibly leads the secondary equipment to error response. Therefore it must choose the TPY class CT which has the transient protective performance. And it's necessary to study the TPY class CT.This thesis concerns for the transient response of the TPY class CT. When fault happens in the system, we should analyze whether the CT could transmit the primary signal rightly and meet the demand of the transient performance. Firstly it introduces the set and the significance. And it recounts some CT models and software using to transient simulation. Then I analyze the equivalent circuit of CT, and represent a method to fitting the curve of magnetization: non-integer power series, comparing with the polynomial approximation method. Then I set up the TPY class CT model, and using Runge-Kutta algorithm to solve the model. Afterwards I use the mixed program of MATLAB and LabVIEW to carry out the program. Then I simulate two windings of a TPY class CT with this program, gain their transient response and analyze the result. Finally I find every error and evaluate them. And I find out the main factor of the error.This thesis recommends the method of completing a CT simulation program in detail. We can spread it to the voltage transformer and other similar electric appliance.