Study On Current Transformer Based On Optical Fiber Thermometry

As the capability and voltage level of transmission lines increasing,conventional inductive current transformers have several draws at extra-high voltage,and particularly ultra-high voltage grades.High voltage elecronic current transformers(ECT) replacing conventional transformers will be the certain developing tendency.However the unsolved problems are in the way to ECT's practicality up to the present time.A high voltage current transformer project based on current thermal effect was introduced,which combined the current thermal effects and the optical fiber thermometry technology.Fiber optic temperature sensor was the earlier and the mature product among fiber optic sensors in commercial,current thermal effects technology is more general applied,so the new project has the advantages over other current transformer projects which are now meeting the difficulties hardly to resolve.It can be used to measure direct current is another significance advantage.The relationship between the instantaneous value of measured current and the temperature rise was deduced,and the mathematical model of the current transformer was established.By use of the mathematical model,in theory,the amplitude of instantaneous current can be tracked by the temperature output of sensor accurately,so that it can be used to measure the absolute value of instantaneous current.The technical data and features required of the main devices and components can be provided by use of the mathematical model for technical design of the project,simulation method and experiment tests were used to prove the available.The realization of the main devices and components were analyzed.The thermodynamic properties of the current temperature conversion device were calculated by the ANSYS software,the mature Rogowsky's coil or ohmic shunt was used as the current sample device.The design requriements and commercial components's technical parameters were analyzed. Fluorescent decay temperature measurement principle was used to measure the temperature,for improving the performance of this kind of method as it has not yet reach the theoretical predict,an optimization method of enhancing the performance was brought forward,which including:(1) The trend of non-exponential variation of the actual fluorescent decay curve is the main factor leading to the result that the temperature measurement performance is not as good as describe by theoretical predict.This result can be used to promote the performance of the temperature measurement system.(2) A cutting and normalized method is given by graphic and caculating to get the numerical factor about the non-exponential degree of the fluorescent decay curve.It can be use to select the predominance fluorescent materials.(3) The concept of the matching of physical reality with mathematical models and data-processing methods can effectively raises the temperature measuring performance.(4) Experiments and simulations proved the effectiveness of the above theory and method.Applied possibility in AC,DC and harmonic wave by using this project were analyzed.The fluorescent decay temperature measurement device was developed,and was assembled into current transformer experimental equipment.The validity of theoretical analysis was proved by the experimental results.