The effect of available short circuit capacity and trail cable length on substation voltage amplification in surface excavation industry

The use of long length medium voltage portable trailing cables in the surface extraction industry to power the major excavation tools such as electric rope shovel, electric drills, electric hydraulic mining shovel, and dragline is indispensable. Since these cables are highly capacitive with low X/R ratio, it is very important to conduct voltage stability analysis before adding a new machine to an existing power system. This paper investigates the effect of the trailing cable length on the mine substation voltage quality. An overvoltage condition which causes the failure of an auxiliary power supplies onboard one of the high power machines is investigated. The possible causes of the overvoltage, predominantly the interaction between current harmonics generated by the use of variable speed drives and the long cable capacitance and substation inductance, is described theoretically and simulated. Power requirements and installation guidelines for high power electrically driven mining shovels is established. On-site measurements are used to validate the theoretical analysis and confirm recommendations.