With the wide application of online monitoring devices for power system, the current transformer (CT) energy extraction has received extensive attention. Whether the current of the transmission line is too high or too low, it makes the CT unable to supply power reliably. Aiming at this problem, the CT with adjustable output is designed to adapt to current fluctuation in this paper. The design consists of three parts: the multi-port CT, the power conversion module and the rechargeable battery. First, inspired by the multi-port transformer in the power system, the number of the CT output ports are set to three. Based on the parameter calculation of the CT, the relationship between the maximum output power and the CT size is given. Then, for the case that the current of the transmission line exceeds the design value of the CT, the related supporting circuit is designed. Finally, a simulation in COMSOL is implemented to verify the correctness of the parameter calculation.
 

power tapping;current transformer (CT);multi-port CT;on-line monitoring devices