138 kV and 345 kV wide-band SF6-free optical voltage transducers

This paper describes the design and testing of novel, environmentally friendly, 138 kV and 345 kV optical voltage transducers (OVTs) for metering and protection relaying applications in high-voltage electric power transmission systems. Each OVT uses three miniature optical electric field sensors housed inside a resistive shield. The locations of the electric field sensors, the electrical and geometrical parameters of the resistive shield, and the formula for deriving voltage from the electric field measurements are all chosen using the quadrature method to achieve very accurate voltage measurements. The resistive shield is, in turn, housed inside a hollow composite insulator filled with low-pressure dry nitrogen. Conventional accuracy and dielectric withstand tests demonstrate that the OVTs meet IEC 60044-7 0.2 and IEEE/ANSI C57.13 0.3 accuracy class standards and insulation requirements. Further tests demonstrate their wide bandwidth (>40 kHz) and show that they successfully reject the effects of the severest possible electric field disturbances on the voltage measurement.