Investigation of overvoltages arising from different neutral grounding methods in medium-voltage distribution networks

Abstract

Relevance: the reliable and safe operation of medium-voltage (6–35 kV) distribution networks is crucial for the overall stability of the power supply system. In this context, the method of neutral grounding plays a key role, as it directly influences the magnitude and duration of overvoltages that occur during single-phase-to-ground faults. Such events can lead to insulation failures, equipment damage, fire hazards, and a reduction in service life. Given the ongoing energy reforms in Uzbekistan—particularly the integration of "green energy" concepts, digital monitoring systems, and energy efficiency measures—there is an urgent need for in-depth scientific and technical investigation into neutral grounding methods and their impact on overvoltage formation. Currently, some distribution networks use isolated neutrals, while others employ low-ohmic resistor grounding. This inconsistency highlights the lack of a unified technical approach, resulting in uncontrolled overvoltages and difficulties in relay protection coordination. Therefore, comprehensive research aligned with technical regulations, safety standards, and international best practices is necessary.

Aim: the primary objective of this study is to analyze, both theoretically and through modeling, the nature, amplitude, and temporal characteristics of overvoltages arising in medium-voltage distribution networks under different neutral grounding methods (isolated and low-ohmic resistor grounded).

Methods: the project employs international experience and advanced technological approaches. Specifically, modern mechanisms for managing electricity consumption are utilized. Statistical methods for comparative analysis and energy efficiency assessment are also applied.

Results: the study incorporates cutting-edge international practices and advanced computational technologies. During the analysis, the amplitude-time characteristics of overvoltages, interphase asymmetry, and the influence of network capacitive currents are taken into account. Furthermore, using statistical and comparative methods, the impact of different neutral grounding methods on relay protection performance and insulation behavior is assessed. Based on local network topologies, practical and region-specific recommendations are developed.