Research On The Key Characteristics Of Fibre Optic Current Transformer

With the further development of the national new-generation smart substation construction,Electronic Current Transformer(ECT),especially Fibre Optic Current Transformer(FOCT),has become the trend of the development of electrical measuring equipment.However,in the present stage,Fibre Optic Current Transformer faces to the problems of environmental interference,on-site construction and installation of non-standard long-term stability,in the engineering applications.To solve above problems,the modeling,simulation,theory,guiding the engineering optimization based on the theory,and FOCT propulsion of practical application have become more and more urgent.In this paper,the basic modeling,transient characteristic,temperature characteristic and primary anti-magnetic field interference ability of FOCT are studied,which provide a theoretical basis for the wider application of FOCT in smart grid.This paper introduces the working principle of Fibre Optic Current Transformer,especially the Faraday Effect and the Sagnac Effect.Then,the main optical components of FOCT are modeled.The FOCT optical path model can be got by analyzing the linear birefringence interference caused by the manufacturing process.Next,according to the simple of FOCT optical path model,the optical part and electronic part are integrated to be modeled.And the overall mathematical model of FOCT is obtained.It provides mathematical basis for the study of FOCT key features.The experimental results show that the established model is in good agreement with the actual FOCT.Finally,the relationship among the main researches,such as the transient characteristic,temperature characteristic and primary anti-magnetic field interference ability is proposed.In this paper,considering the demand of digital saturation and the overall mathematical model of FOCT,the transient characteristic of FOCT are modeled.Then,the problem of coordination between the FOCT and Merging Unit(MU)is discussed and analyzed.Through the experiment,the correctness of the relevant theoretical analysis is verified,which provides the theoretical basis for the further practical application of FOCT.Temperature effects on the performances of all parts of FOCT.In this paper,the temperature influence factors of FOCT were analyzed,including the temperature characteristics of optical components and electronic modules.Then,the sensing loop and the delay fibre of the FOCT are modeled as a whole.And the influence of the temperature on the output characteristic is quantified.As well as,the temperature compensation and suppression methods are carried out in the hardware and software.The validity of the temperature compensation scheme is verified by experiments.According to the physical principle of FOCT,the magnetic field is one of the main factors affecting the FOCT output performance.In this paper,the distribution of the electromagnetic field near the sensing coil is analyzed under several typical external electromagnetic interference,such as the interference of alternating current and the interference of the current loop.An improved distributed parameter FOCT model is proposed to modify the FOCT model,which is proposed in literature.It is more focused on the Faraday rotation angle and lessen the influence of the linear birefringence reduction.Then,it is verified the correctness of proposed model by experiment.In engineering applications,the long-term operation stability is one of the focus points.In this paper,the main factors affecting the stability of FOCT are analyzed.Then,problems of an 110 kV Smart Substation in Guangdong power grid during FOCT's unit acceptance are solved by using the methods mentioned in the preceding chapters to analysis and improve.Finally,the reliability of the proposed schemes is verified by the data of one-year after the operation of the FOCT.