Dry-band arcing in all-dielectric self-supporting fiber-optic cables.

摘要

Utilities frequently install All-Dielectric, Self-Supporting (ADSS), fiber-optic cables on high-voltage lines. Several failures of these cables were reported by the utilities. A survey of technical literature revealed that the fiber-optic cables failed due to two reasons: (a) corona induced damage near the supports at the tower and (b) dry-band arcing caused failure close to the tower.; This dissertation investigates the problem caused by dry-band arcing on ADSS cables strung on high-voltage lines. A novel analytical method is developed to model the electrical environment of the cable. This method includes the effect of different tower arrangements, sag, tower effect, pollution level, span length, and phase sequence. The analysis shows that sag and phase sequence significantly affect the short-circuit current at the towers. It is also shown that the effect of the tower can be neglected. The open-circuit voltage and short-circuit current increase non-linearly with span length and pollution level. A test method is developed to study dry-band arcing on the cables. Cable samples are cyclically subject to wetting, drying, and arcing. The cable dries from the top forming a thin layer at the bottom. This layer dries slowly and a dry-band arc is eventually formed. The arc length at start is around 0.4 centimeters and increases exponentially with time to a stable length. A quadratic relation between the stable are length and voltage is derived. A mitigation method is presented for reducing the risk of damage due to dry-band arcing. This method has been experimentally verified. Future work to advance knowledge in dry-band arcing on ADSS cables is also presented.