CT Modeling And Its Application In Draw-out Power Supply Of Transmission-Line

This paper is focused on theory and model of ferromagnetic material, CT modelingand its application in on-line draw-out power supply of transmission lines. In order toanalyze transfer characteristics of CT, CT model including hysteresis is establishedbased on modified J-A static model of core. Then impact of air gapped CT parameterson its power transmission characteristics is studied for optimization of draw-out CT andcircuit design in power supply. Compared with classical static hysteresis Jiles-Atherton(commonly called J-A) model, modified J-A static model is more close to realhysteresis loop, especially in minor loop. Numerical CT model with high accuracy isachieved by coupling modified J-A quasistatic (50Hz) model with transfer equations ofCT and verified by measured data. By using draw-out CT with optimized structure andPCB board for power transformation and control, reliability and stability of on-linedraw-out power supply is obtained.The main contents and outcomes are listed as follows：①Mechanism of hysteresis and magnetization is analyzed based on current theoryand model of ferromagnetic material. Then, tranditional anhysteretic J-A model andclassical static hysteretic J-A model are studied in detail. Modified J-A static modelwith H as argument is derived by modification to unphysical solution in minor loop andloss factor k in classical J-A static hysteresis model, and modified J-A dynamichysteresis model is studied as well. Besides, analysis of magnetic core with intentionalair gap shows that saturation problem of continuous core is overcomed by using air gap.②Differential equation describing transfer characteristics between primary andsecondary current of CT is derived based on basic principal of electromagneticinduction. Then, transfer equation is coupled with modified J-A quasistatic (50Hz)model to establish numerical model of CT. To help use of CT numerical model,graphical user interface of CT model is also achieved by using Matlab/GUI work-box.③Output power equation of air gapped CT is derived when consideringpermeability μ as constant and power transmission characteristics is obtained bymeasuredPo Rocurves. Then combinative power supply scheme which integratespower supply based on DCT with Li-battery group is proposed to accommodate widedynamic current of transmission line. At same time, decrease of switch times of CTratios and charge/discharge times of Li-battery are respectively realized by employing sluggish comparator I and sluggish comparator II.