For monitoring temperature

insulation and mechanism of medium voltage switchgear

an on-line monitoring system was developed.Based on the low power electronic devices and infrared communication

a contact-type temperature sensor with high precision was designed for the system to solve the problem of high voltage isolation.An angular displacement sensor was used to measure the travel-time curve of the movable contacts indirectly

leading to the solutions of the problems in sensor assembling and high voltage isolation.Furthermore

combining with the vibration signal and the current curve of tripping coils during operation

the monitoring of mechanism condition of medium voltage switchgear could be achieved.The insulation could be characterized by measuring the leakage current of bushing.The test indicates that the on-line monitoring system is stable and reliable.