Effect ofElectrode Shape on Medium Voltage Covered Conductor Insulation Durability Under Electric Stress

Covered power line conductors aid in maintaining normal operation in case of objects coming into contact with phase conductors. An electric test was conducted where various types of grounded electrodes were brought into contact with the insulating layer of the covered conductor. The conductor was energized and the cumulative time was measured until insulation breakdown occurred at the contact point of each of the grounding electrodes. Five different types of electrodes were used. Three of these were round in shape and were used for simulating tree branches with different diameter. One electrode was a copper wire winding specified in covered conductor testing standard and one was aluminum tape. A total of 10 electrodes of each shape were used for better estimation of the variability of breakdown time. The average breakdown times of each type of electrode were notably different but also the variability of breakdown times in case of electrodes of the same type was quite substantial.