Covered Conductor Burn-Down Phenomena in Indonesia without Protection Relay Operation

Abstract

All Aluminium Alloy Conductor-Shielded (AAAC-S) which is covered conductor is widely used as the temporary solution to mitigate the earth fault problem during application of bare conductor in Indonesia distribution system. However, the burn-down phenomenon of AAAC-S is often found in some cases and the protection schemes that have been installed on the distribution line is unable to detect any fault during the phenomenon. Due to no tripping order from protection relay, this phenomenon will lead some part of the conductor remain hanging in the air and still in energized condition. This condition may cause a potential hazard to the surrounding environment. Therefore, this study was performed to determine the cause of AAAC-S burn-down and the reason of protection equipment cannot work properly. Field investigation, modelling and simulation, and laboratory testing has been performed in this study to represent the condition in the field. The results show that the burn-down phenomenon of AAAC-S occurred due to many sequences of events. It started with insulation material breakdown that create pinhole, then during overvoltage phenomenon there will be earth fault condition through the pinhole. Finally, if the short circuit energy at a certain mechanical tensile exceeds the critical energy of AAAC-S, then the burn-down phenomenon occurred. In this condition, the protection relay is unable to detect the fault due to the working time of protection relay is greater than the critical burn-down time of AAAC-S, where it is being influenced by the location of earth fault, cross-sectional area of AAAC-S, and grounding resistance of the pole.