Identifying ground-fault locations: Using adjustable speed drives in high-resistance grounded systems

One of the more difficult problems to solve in industrial plants is how to identify and eliminate ground faults in a high-resistance ground (HRG) system. This is because ground-fault conditions in these systems do not draw enough current to reliably trigger fault current sensors in the drive. This article develops an approach to identify the ground-fault location in HRG systems using voltage sensing, rather than current sensing techniques, inside an adjustable speed drive (ASD). This approach consists of a simple analog circuit and digital signal processing technique to detect a fault condition, as well as to identify the fault location, be it on the load motor side, inside the ASD, or ac line side. The use of this ground-fault identification method is also extended and discussed for application to multiple drive lineups.