The setting value of self-adaptive 20 Hz generator stator ground fault protection proposed in this paper can automatically vary with different grounding positions. Regardless of the grounding positions， it can ensure that the protection will quickly operate when the grounding current is greater than the allowed safety value.This new scheme can overcome the defects of traditional protection and remarkably improve the operation security of generators. Some key technologies are analyzed in detail， such as the calculation method of zero-sequence potential at the grounding point， the association between operation equations， the analysis of why the grounding point parameterα has significant influence on protection characteristics while not appearing in the operation equations.