Non-contact measurement of lightning and switching transient overvoltage based on capacitive coupling and pockels effects

Measurement of lightning and switching transient overvoltage in power system is significant to the research that guides the protection of power system. Anew type of sensor for non-contact measurement of lightning and switching transient overvoltage in power system is designed in this study. This sensor is composed of two parts, namely, voltage induction and optoelectronic conversion units. Given the existing stray coupling capacitor C-1 between the transmission line or bus bar and a metal plate placed under it, a voltage induction unit is designed by utilizing the C-1 and a capacitor with fixed value C-2 connected in series, then the high-voltage non-contact induction on a transmission line or bus bar is achieved. The optoelectronic conversion unit is designed based on the Pockels effect of the LiNbO3 crystal. The voltage signal induced by the voltage induction unit can be converted to an optical signal by the optoelectronic conversion unit for long-distance transmission through optical fibers without power supply at the monitoring site. Laboratory and field tests revealed that the new developed sensor possesses good linear region, high precision, and wide frequency band of the response to lightning and switching transient overvoltage in power system. The sensor can also be applied to the non-contact measurement of lightning and switching transient overvoltage in power system with different voltage levels by conveniently adjusting the distance between the sensor and the line. (C) 2015 Elsevier B.V. All rights reserved.