On-field instrument transformers calibration using optical current and voltage transformes

This paper presents the development of a system based on optical current transformers (OCTs) and optical voltage transformers (OVTs) for on-field calibration of conventional instrument transformers (ITs), avoiding necessities of removing the equipment for laboratory environment and interruption of supply for on-field calibration procedures. To accomplish these aims it was required the development of suitable OVTs and OCTs with accuracy classes equal to or better than 0.03%, suitable for calibration of conventional ITs intended to supply measuring instruments (accuracy classes equal to 0.3^%). It was also necessary to develop the appropriate methodology to perform expedite on-field calibration of conventional ITs without interruption of service. As a further result of project, the on-field calibrations results may provide to sponsor utility recommendations for its maintenance procedures, aimed at replacing the identified off-class ITs or allow the use of algorithms for errors/losses compensation to be implemented on measuring instruments, in case of such resource be available.