Detecting internal defect of non-ceramic insulators using a novel micromachined electric field sensor

The paper presented a novel MEMS (Microelectro-mechanicalsystems) electric field sensor (EFS) based on SOI (Silicon on Insulator) fabrication process for detecting internal defect of non-ceramic (composite) insulators. The ability to measure both AC and DC electric field is a significant advantage of this sensor in comparison to other sensors, which can only measure either AC or DC electric field. The MEMS structure is designed to work at resonant frequency for maximum sensitivity to electric fields. Prototyped by the SOI fabrication process, the device gives high quality factor (Q) of approximately 31034 at a vacuum degree of ~1mTorr with lower actuation voltages (i.e., 250mV DC and 20mVp-p). The sensing area of this sensor is only 5mm×5mm and it requires only less than 1μW to drive its shutter. Tested in ambient air conditions, a minimum detectable DC and AC electric field with current sensor designs better than 50V/m is also achieved. The use of a miniature sensor also helps to measure local electric field around insulators accurately since the field distortion caused by the sensor is minimum. Experiments show that the EFS probe can be succeeded in detecting the internal defect of non-ceramic insulators remotely.