Abstract The paper analyses the detremination of CT’s parameters for the distribution transformer primary side with several samples, lists detremination steps, illustrates that parameters of CT should be determined according to the actual situation of the project, and the second rated current should be selected for 5A according to the actual load of the CT’s measurement winding. The determination of CT’s rated primary current is not only depended on the transformer’s rated primary current, but also unusually related to the relay protection setting. So, the accuracy limit factor is determined by the maximum setting values of relay protection, the microcomputer protection relay’s range should be considered when the rated accuracy limit primary current is determined, rated transformation ratio should be increased properly, and the CT’s parameters are determined after review and check. The application effect of this method is reasonable on technology, applicable and economical.
2015, Vol. 16 
