Ground Fault Detection and Protection In Vfd

Abstract

Now a day, many low-voltage (LV) adjustable speed drives (ASDs) have a built- in ground-fault function that is not capable of detecting a low-level ground fault and may require the use of a suitable supplemental protection relay for reliable detection. The different system grounding techniques are discussed. From all the discussed techniques, High Resistance Grounding (HRG) is the preferred method of grounding in several industrial power distribution systems because of safety and reliability concerns. One of the more difficult problems to solve in industrial plant is to locate and eliminate a ground fault in High Resistance Ground (HRG) system. This is because a ground fault conditions in these systems do not draw enough current to reliably trigger fault current sensors in the drive. The various approaches to identify the ground fault in HRG systems are studied. A fault detection technique is developed based on extracting the fundamental component and third harmonic component and compared to the set threshold. When the value is higher than the set threshold it indicates a fault in a system and system shuts down.