Electrical insulation is an important part of all electrical systems. The level of insulation safety provided by an insulator depends on the amount of leakage current flowing on its surface. Actually increased leakage current causes a part of high voltage to appear at dead end of insulator. This voltage may sometimes be of order of 1000 to 5000 Volts depending upon weather conditions. Such a level of leakage current causes hazards to public safety as well as losses. So to monitor and keep the leakage current low is an important parameter to be considered by designers and electric supply companies.

Particular focus has been made on leakage current monitoring of composite 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 ultra bright 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. 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.