Malfunction Analysis of Generator Third Harmonic Stator Grounding Protection

The third-harmonic stator grounding protection is widely used in China to monitor the stator insulation of the generator. This protection would send wrong signal in engineering applications. This paper introduces the principle and implementation method of the third harmonic stator grounding protection. According to the generation mechanism of the third harmonic electric potential of the generator, this paper analysis the Various influencing factors of ratio calculation principle, and fixed value optimization advice of the third harmonic stator grounding protection is proposed. Fixed value optimization in engineering applications also recommended.