Impact Evaluation of the Neutral-Grounding Resistance on Short-Duration RMS Voltage Variations

Neutral-grounding resistors are employed on transmission, distribution and industrial electric power systems to achieve, among other goals, a limited magnitude of the ground-fault current. The impedance connected between a neutral point and the ground influences the total zero-sequence impedance of a system, which impacts voltages during ground faults. Therefore, there is a relation between the grounding scheme and voltage disturbances, like the short-duration rms voltage variations (SDVVs), which include interruptions, sags, and swells. Hence, this paper presents an analytical evaluation of the influence of the neutral-grounding resistance on SDVVs during single-phase-to-ground (LG) and two-phase-to-ground (LLG) faults for an industrial system. It is observed that the influence occurs mainly on phase-to-ground voltages, there being an impact on phase-to-neutral or phase-to-phase ones just for a few values of fault resistance. The results thus indicate better neutral grounding practices for industrial systems and show the best load connections, concerning SDVVs and equipment tripping.