SF6-free 550 kV combined optical voltage and current transducer system

A three-phase optical voltage and current transducer system (NXVCT) for accurate metering of a 550 kV power transmission line is described. Extensive laboratory tests were performed on these units. Accuracy tests on the optical voltage transducers (OVTs) show compliance with IEC 0.1% class requirements with respect to linearity over the extended dynamic range of 10%-150% rated voltage, and with respect to accuracy over temperature, from -40 °C to +60 °C. The NXVCTs also passed a series of standard high-voltage type and routine tests, including one-minute AC withstand at 800 kV, lightning impulse tests at 1800 kV, chopped impulses at 2070 kV, wet switching impulses at 1250 kV, and RIV tests. This NXVCT system is now installed in a 500 kV substation.