Research On Adaptive Electronic Current Transformer Based On Rogowski Coil

With the rapid development of the electrical power system, the demand of responsing ability of measuring devices become higher. Because rogowski coil current transformers not due to saturation, good linearity, and dynamic capabilities. So they are attracting increasing attention. However, the measurement precision of rogowski coil current transformer is vulnerable to be changed in the external environment. And the measurement results when small current is not very good. On this issue, this paper launches a study, and designs an adaptive correction rogowski coil current transformer.Firstly, core rogowski coil current transformer is chosen to be the reference. By lots of simulation of its equivalent model, the result shows it has high precision when the core rogowski coil is not saturated. So it meets the demand of adaptive system. But when electrical power system is fault, core rogowski coil is easy to be saturated. In order to judge the saturation point, fast multiresolution wavelet analysis method is used. The result of simulation shows that it is feasible to use fast multiresolution wavelet analysis to judge the saturation point.Secondly, the influence of external factors can decrease the measuring precision of heart rogowski coil by analyzing the equivalent model of heart rogowski coil. Control principle is applied on current measuring system of rogowski coil. Heart rogowski coil combines with core rogowski coil. Then adaptive rogowski coil current transformer is designed. The result of simulation shows that adaptive system can revise the error brought by external factors and improve the measuring precision of rogowski coil current transformer.Based on the research of the above two sections, structure of adaptive rogowski coil current transformer is designed, and studies on integral circuit and modulation circuit especially. The integral circuit with inertial link can recover the output voltage to be the signal proportional to the measured current. Modulation circuit transforms the analog collected to be digital suitable for optical fiber transmission. A/D7895-10 is chosen to be the chip according to the measuring demand. Then pulse generation circuit which is needed by chip is designed. The result of simulation shows that the designed circuit can provide pulse for A/D chip effectively.