Effect of Surface Resistance on the Surface Voltage in an Insulated Overhead Conductor

Recently, insulated covered overhead conductors are gaining momentum instead of bare overhead conductor due to several advantages associated with them like improved power system reliability and other environmental aspects. Under normal conditions, the insulation surface of the covered conductor will be affected by different stresses like electrical, mechanical, environmental etc. Covered conductors are not subjected to confined electric field as in underground cables. However, there will be leakage currents, both insulation and surface due to the above-mentioned stresses which will cause degradation of the insulation of the covered conductor. In this paper, surface voltage measurements have been done on an insulated covered conductor. Simulation of the insulated covered conductor using equivalent electrical model of the covered conductor has also been done and the results of the simulated values are found to be in close conformity with the experimental data. Using the equivalent circuit, the effect of surface resistances on the surface voltages and surface leakage currents have been simulated. Interesting results on the role of surface resistances are presented. It is shown here that a lower surface resistance may cause a higher stress to the surface insulation of a covered conductor.