Abstract: A fault of Guangdong Zhuhai Jinwan Power Generation Corporation Limited, which caused the stator earthfault protection acted, was analyzed, and the analysis proved that the protection acted correctly and timely. Starting from the questionable point that the fault phenomenon was not accordance with the actual inspection, by using the vector diagram, according to the intuitive analysis, the fault process was determined that the opencircuit fault was occurred first, and then the shortcircuit fault occurred. By further analysis, the conclusion obtained that the protection action process was fully accordance with the field inspection result, and it is verified that the settings of stator earthfault protection is correct.

Key words: stator earth-fault protection, zero-sequence fundamental harmonic, third harmonic