Calibration And Optimization Of Optical Current Transformers

Precise and accurate current measurement and metering is one of the considerable goal of power systems.Therefore there must be a robust and timely current measurement systems for power systems.Because the power systems protection is one of the main and necessary requirements that can't be ignored and need an utmost attention.Till now mostly the traditional CTs are used for current metering and protection purposes.However they can't met the measuring requirements of advanced and huge power systems and due to certain limitations like the saturation of magnetic core,the hysteresis effect,and inability to measure AC and some other issues are not giving optimized measurements and results.OCTs(Optical current transformers)and FOCTs(fiber optical current transformers)have certain advantages over the traditional electromagnetic CTs(current transformers)and overcame the certain limitations of CTs and have given effective measurements.Therefore it is inevitable to replace the CTs with OCTs and used them practically and install in our power systems.Although the OCTs are comparatively effective than traditional CTs but unfortunately the optical current transformers are also facing some problems and need more research and optimization.In this paper firstly the working principle of OCTs is analyzed and the problems OCTs and FOCTs are facing is explained.The factors(like the birefringence due to temperature and stress,magnetic interference)effecting the measurement accuracy and the long term stability of OCTs is discussed and different techniques have been proposed.Furthermore it is analyzed that up to what extent its accuracy and measuring capability is effected by which factors and up to what extent they can reduced and minimized.A brief summary is presented for its optimization and future solutions are proposed for its accurate and precise measurement and efficiency.Secondly with the help of LabVIEW an intelligent calibration system of optical current transformers is designed according to IEC and IEEE standards through which we can check the accuracy and error analysis of OCTs.LabVIEW(Laboratory Virtual Instrument Engineering Workbench)a graphical user interface programing tool in which we have design an intelligent verification systems of optical current transformers and have checked its accuracy and errors like RE(ratio error)and PE(phase errors).In order to develop complete and effective calibration system,first we analyze the test standards of optical current transformers and the standard conventional current transformers.After that both the transformer are compared data is collected,analyze signal,calculate error and store results.As the practical or on field calibration systems have many errors due to signal processing and environmental noise simulation based analysis are preferred.It is further verified that it is reasonable to design a LabVIEW based calibration systems.to test optical current transformers.As it compatible with the development trend of smart grid and power systems and also support the DAQ for practical measurements and instrumentation.