Neutral Grounding Resistor Monitoring Based on Sub-Harmonic Signal Injection

Abstract

Neutral grounding resistors play a critical but often undervalued role in power systems by controlling the severe transients that appear in neural system. Continuity of service of these key assets should be ensured since the defected neutral grounding resistors leave the system unprotected against transient overvoltages and overcurrents and cause false sense of security. An efficient solution is proposed to detect this issue for unit-connected generators that are equipped with the subharmonic injection based generator stator ground protection. The proposed technique demonstrates reliable performance for various conditions of the resistor and power system, observed through comprehensive software analysis. In contrast to existing methods, this technique relies on existing protection and monitoring installations making it an efficient alternative that first, adds more value to existing sub-harmonic injection infrastructures and second, initiates an alarm and prevents ground fault trip in case of failed-short neutral grounding resistor.