Transient Voltage Measurements for Overhead Transmission Lines and Substations by Metal-Free and Contactless Integrated Electro-Optic Field Sensors

Measuring the transient voltages, including lightning or switching impulse overvoltage, is helpful for accident analysis of power system and insulation design. In this paper, a contactless transient voltage measuring system based on a metal-free integrated electro-optic electric field sensor was proposed, implemented and tested. The lightning and switching impulse transients are proportional to the electric field they generate and vice versa, enabling measurement of the transient voltage by measuring the associated electric field. The proposed method uses an electric field sensor to directly measure the field generated by the voltage without any capacitive coupling. In addition, a method to decouple the multiphase coupling was proposed. The performances of the measuring system were tested by simulation experiments and compared with that of a standard divider. The field data of the transient overvoltage on a 220 kV bus during the process of putting a capacitor voltage transformer into operation were given. The measurement results were found to coincide with the related physical process.