In view of the advantages of optical fiber voltage transformer

the auther paper presented a scheme of real time phase measurement for high voltage grid based on optical fiber voltage transformer.Three phase voltages were detected on high voltage side by optical sensing head based on electro-optic effect.The modulated optical signals were turned into electric signals

and were converted to the corresponding digital signals via an AD converter.After αβ coordinate transformation

the orthogonal component was sent to an automatic phase tracking system to realize phase lock of utility voltage.A mathematical model of automatic phase tracking system in frequency domain was built

and the stability was analyzed through simulation.The simulation result shows that the magnitude-frequency characteristic in low frequency bandwidth is satisfactory and the phase is stable.The system could be used to monitor and control high voltage transmission and distribution grid.