Long Wire Antenna-Like Behavior of Uninsulated Overhead Distribution Cables

Uninsulated overhead distribution cables are evaluated in terms of their propagation and radiation behavior when excited by a partial-discharge (PD) pulse. Low attenuation levels at high frequency and a traveling-wave radiation pattern are observed for a single aluminum cable. The dominant radiated frequency components of surface discharge and dryband arcing are experimentally evaluated, and a high level of activity is observed in the 400-600-MHz and 900-1000-MHz bands. High directivity values at specific angles are also recorded at 400 and 900 MHz for single- and three-cable distribution systems. These findings show that a PD signal will travel for a significant distance along a cable and leak radiation predominantly in a specific direction, thus assisting the design of the RF-based discharge detection and localization system.