The Research Of Current Sensor With Single-Turn-Cored Structure Suited For Tiny Current Based On Zero-Flux

Current sensors play a very important part in the on-line insulation monitoring of electric power transmission. Generally they are used to measure leakage current of ground wire. At present, use current transformer as insulation monitoring current sensor mostly. For not changing the connection of the apparatus be measured, chooses the current transformer with single-turn cored structure. Leakages of HV apparatus are between severalμA and hundreds mA commonly, which is too small to be measured by ordinary current transformers. To get a tiny-current high-precision current transformer avoiding electromagnetic susceptible,performance instability,short life of electronic ones, studies high-precision passive current sensor with single-turn cored structure by reducing its secondary turns.Based on the zero-flux current transformer principle, propose a passive zero-flux compensation method and deduced it. Designs a current transformer with 500 turns based on this method. The verify experiment proves that its ratio and phase characteristics are much better than ordinary ones and the precision is enough for measure use. Zero-flux current transformer can't obtain absolute zero flux because residuary flux, so when the secondary turns is too small it will not satisfying. To improve the precision further, proposes a method to compensate zero-flux current transformer using capacitance parallel connected coil and deduces it. Designs a current transformer with 100 turns based on the method. The experiment proves this theory can improve ration and phase characteristics of the zero-flux current transformer. The secondary turns reduces form thousands of ordinary current transformer to 100 through my work..Studies the shield and anti-jamming techniques and designs the shield shell. Designs the transmit microcircuit adapts to the far distance transmission.Using the passive high-precision current transformer founds a method to measure dielectric loss based on FFT which can eliminate effects of harmonic and current frequency excursion and conducts an experiment.