Sensor design for leakage current measurement on ADSS fiber-optic cable

All-Dielectric-Self-Supporting (ADSS) fiber-optic cables are installed on high voltage transmission lines for communication purposes. When the cables become polluted and wet, a conductive layer is formed on the cable. Currents are induced on the surface of the cable leading to dry-band arcing. A comparatively large number of fiber-optic cable outages have been reported in UK near sea-coasts, and it is believed the dry-band arcing is the responsible for the damage. Knowledge of the leakage current levels on the cable surface before dry-band arcing can be used to predict cable failure. Monitoring the leakage current can also yield information on the aging of the cable. This paper presents a review of three different current sensors that can be used on ADSS cables, which include a simple shunt resistor, an active Rogowski coil, and a double core sensor. The frequency response and output characteristics of the different sensors are presented. A current monitoring system is designed and constructed for use with ADSS on high voltage transmission lines. A shunt resistor is used as a sensor. The system is self-contained and consists of a solar panel, data acquisition system and cellular communications. The system has been tested and its performance is presented.