Development and Pilot Operation of a Three-Phase Fully Optical Measuring Voltage Transformer of 220 kV with Digital Output

Abstract

An electronic three-phase fully fiber-optic measuring voltage transformer (FOVT) of accuracy class 0.2 for a nominal voltage of 220 kV with a digital output for operation at power system facilities, including electrical substations, is described. The operation principle of the device is based on the use of a longitudinal linear electro-optical effect (Pockels effect) for measuring AC voltage. The fiber-optic measurement scheme based on low-coherent interferometry is connected via a fiber cable to an optical high-voltage primary converter (HVPC) with an electro-optical crystal placed in it; there are no additional voltage dividers inside. The digital signal processing unit (DPU) contains optical and electronic circuits for generating, detecting, and processing an electro-optical signal. FOVT has a digital interface that complies with the IEC 61950-9-2 LE standard, and can be used as a component for the Digital Substation and Smart Power Grid technologies. The design features of the HVPC and the DPU are described and the results of the metrological characteristics of FOVT-220, based on the data obtained during the certification and pilot operation at the 220 kV electrical substation, are presented.