Siroos Rahimi-Taghaniaki - Ahvaz Electrical Distribution Company Ahvaz, Iran
Seyed Ghodratolah Seifossadat - Shahid Chamran University of Ahvaz Ahvaz, Iran
Arash Rohani - Khuzestan Regional Electric Company Ahvaz, Iran

This paper investigates the influence of rectifier diode failure in ground fault detection method in the excitation system for synchronous generators with static excitation. The detection method is based on the frequency analysis of the first and third voltage harmonics at a grounding impedance placed at the excitation transformer neutral terminal. Due to the effect of a short circuit or an open circuit in rectifier diodes on the fault side (AC or DC), the detection method makes a mistake in identifying the side of excitation fault. The object of the proposed method in this paper is to identify the side of ground fault in excitation, while there is a short circuit or an open circuit in one of the diodes. The accuracy and applicability of the proposed technique is demonstrated through both computer simulations and experimental tests.

synchronous generator protection; synchronous machine excitation system; ground fault detection; failure in diode