Grounding Current of Converter Transformer Core and Core Clamp and Its Harmonic Characteristics

The energized test of grounding current of converter transformer core and core clamp is helpful to detect the grounding fault of converter transformers. In this paper, the grounding current of core and core clamp of tens of converter transformers in a ±500 kV and ±800 kV converter station were measured and corresponding harmonic characteristics were obtained, respectively. The results showed that the grounding current of core and core clamp contain a lot of harmonics. The fundamental current is much smaller than the total grounding current as the harmonics contribute much to the total grounding current. The harmonics contained in the total grounding current of core and core clamp should be considered together with its fundamental current when condition assessment is performed for converter transformers.