Research and Development of Optical Current and Voltage Transducers for Electrical Power System

In electrical power industry,optical sensors are inherently advantageous over conventional measurement techniques.In this paper,the research and developments of some high voltage optical current and optical voltage transducers are reported in detail.A three-phase optical current transducer was developed and put into use in a real 110kV electrical substation.The calibrated ratio errors within rated current range is less than 0.2%.By employing optical insulators,the optical current transducers are with good insulation,light weight and small size.At the same time,the combined current and voltage optical metering unit(OMU) for 500kV power system is presented.In the OMU,the BGO cystal and flint glass were used as sensing elements for high voltage and electrical current,respectively.The experimental results showed that both optical current sensor and optical voltage sensor were of good linearity.The specifically designed insulator for 500kV high voltage system was a optical insulator embedded in a conventional porcelain column.Some new technologies used in optical current sensors recently are discussed as well.These new sensors include:bulk glass optical current sensor with an adjustable multi-ring closed optical path,hybrid type bulk glass sensor with multiple critical angle reflections for sensitivity enhancement,right-triangle shaped detachable Faraday effect current clamp and fiber Bragg grating based magnetostrictive sensor for DC current measurements.The optical fiber technology used in power system in the future for optical sensing,optical monitoring,optical communication,optical relay protection and optical local area network are introduced as a conclusion.