Computer simulation of fiber-optic cable failures due to dry-band arcing

Utilities frequently use ADSS (all dielectric self-supporting) fiber-optic cables installed on transmission lines 10-20 feet below the high voltage conductors. A grounded armor rod assembly supports the cable at each tower. Dry-band arcing occurs on the fiber-optic cables when the cables are polluted and wet. This has been assumed to cause cable failures. The objective of this paper is to present a computer model and simulation results for the investigation of dry-band arcing. An equivalent circuit has been developed to represent the polluted fiber-optic cable in the high voltage environment. The circuit has been simulated using a commercial circuit simulator. The voltage and current distribution along the fiber-optic cable is presented. The effect of pollution levels on voltage and current is analyzed. It is also shown that the span length has an effect on the voltage and current and consequently dry-band arcing. These results could be used to determine whether dry-band arcing is a problem for a given span length. The tower has a significant effect on the capacitance to ground of the fiber-optic cable. However, it is shown that this does not affect the voltage and current distribution for pollution levels heavier than 10⁸ n/m. This model can be used by utilities to predict dry-band arcing in fiber-optic cables