Transient voltage measurement for UHV AC substation using non-contact electro-optic field sensor

The transient voltage measurement for UHV AC substation is significantly important for the insulating of electric equipment. This paper proposed an improved non-contact field sensor. A y-cut z-propagation lithium niobate (LN) crystal is used as electrooptic crystal and the type of common path interferometer is adopted. Two plate electrodes are placed between the LN crystal parallel to x-axis, which decreases the signal induced by the electric filed from the undesired direction. The sensor was verified by laboratory experiments, and it has good performance under different waveform and frequency. The sensor was applied to measure the switching transient voltage in a UHV AC substation during the system tests. the waveforms of transient voltage during breaker-closing and -opening processes were obtained and compared with the waveforms from CVT. The results showed that the sensor could measure the transient voltage with high accuracy, which can be used to monitor the voltage for UHV AC project.