In this paper, internal fault protective relay maloperation of assembling capacitor bank caused by switching-on transient harmonics is analyzed. Mathematical expressions describing the adaptive settings of single-wye, dual-wye and bridge connections are given. The realistic action of internal fault protections under high amplitude harmonic conditions is possibly very different from theoretic setting. Major impact of harmonic is to change the maximum allowed fault units in the capacitor banks on which the relay action settings are tight depend. The paper deduces this change under harmonic condition and actual investigation results corroborate the rationality of the research work. Corresponding measure against the relay maloperation is discussed.
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