Current Transformers For Transient Performance And Protection Effects Of Computing And Research

Current transformers (CT) are very important instruments in power plant and transformer substation. In normal operation, current transformers can transfer current as expected. However, because of the built-up of nonlinear core in current transformers, when a fault occurs, their nonlinear characteristic is likely to cause saturation and subsequently substantial errors in the magnitude and phase angle of the generated signals. Especially in low and middle voltage, the CT ratio is limited by the scale margin. But as the growth of the power system, the fault current increases a lot which is much bigger than the rating current of CT. And it makes saturation occur not only in transient but also in steady state sometimes (especially in transient) . As a result, delayed operations, or failures to operate of the protective relays may happen. The paper analyzes and computes the transient procedure, pointing out some views through analyzing the existing recognizing and disposing methods of CT's saturation. Besides, the paper simulates the act of main factors to CT's saturation.Optical current transducer is a new kind of current transformer. It has a lot of merit which traditional CT cannot compare with. The passage describes the development of OCT and its principle, then give an method which use OCT to replace traditional CT to solve the problem of CT saturation o...