Detection and Monitoring of Leakage Currents in Power Transmission Insulators

An optoelectronic sensor for real-time leakage current monitoring on high-voltage (500 kV) and medium-voltage (13.8 kV) power line insulators was developed. The leakage current drives an ultrabright light-emitting diode producing an amplitude modulated light signal. The optically intensity-encoded signal is coupled to a plastic optical fiber cable and transmitted from the high potential measurement point to the remote unit in ground potential. After the demodulation, the leakage current root mean square values are concentrated in a data logger and sent to a remote station 150-km away by general packet radio service technology. Field tests at real operational conditions on coastal regions have been performed; all data collected are stored in a structured database, which can be consulted from the Internet, while a serially produced head was developed and the sensor is ready for commercialization. Since leakage current on high-voltage insulators depends on local air pollution and microclimate changes, several sensors have to be used to cover the region monitored. For this reason, research has been conducted to determine the sensor representativeness, i.e., the actual area, which can be covered by only one sensor.