Research On Power Supply Of Optical Fiber Current Transformer

With the rapid development of the national economy,higher requirements are put forward for the safe and reliable operation of the power grid,and the concept of the smart grid has emerged.In order to ensure power supply reliability,a large number of online monitoring devices are required to provide real-time data.On-line inspection equipment is distributed around power cables.Cables are often located in underground or field environments,and conventional power supplies are difficult to supply power to equipment.In the high-voltage,strong magnetic field environment,how to supply power to the equipment becomes a key issue.In the existing power supply mode,the current transformer is used to induce the primary current in the transmission line to the low voltage side,and the power supply has higher power,smaller volume,lower long-term use cost,and better practicability.However,the range of the busbar varies greatly,usually thousands of amps in a few amps.If the minimum starting current requirement of the device is met,the input current is often accompanied by core saturation and deep saturation.The core heating and ferromagnetic resonance caused by the excitation current during saturation not only affect the life of the power supply,but also the power output of the core.In the design of the existing CT power supply,the calculation and analysis of the output power of the iron core in the saturated state can only be realized by the external power supply circuit and the load measurement method.This method is not conducive to the selection of the iron core and the power supply parameters.This paper first analyzes the principle of induction power taking,establishes a circuit model,and analyzes the influence of parameters such as core size and load resistance on output power and saturation.The magnetic circuit model is established to analyze the influence of air gap on power and saturation in the air gap core,and the formula containing air gap parameters is derived.Secondly,in the simulation software Ansys EM,the closed iron core and the model with air gap core are established,and the primary current,load resistance,core size and air gap size are changed,and the secondary side voltage amplitude and waveform change are observed.The power and saturation effects of each parameter are verified,and it is verified that the method of using the air gap can effectively reduce the saturation of the core.The accuracy of the model is verified by comparing the measured results with the simulation results.The model parameters of the power supply design can be determined by this,and the core and power supply parameters satisfying the power supply requirements can be effectively determined.Thirdly,a design scheme of the energy-capturing CT is proposed,so that the power supply is operated at the maximum power point when the bus current is small,and the starting current can be reduced.It can be seen from the experiment that the designed power supply can adaptively output5 W power under the large fluctuation of the bus current,and the magnetic core has no obvious heating phenomenon.According to this method,it is possible to design power supplies with different power outputs in different scenarios.