The newly-built GIS and the original part are isolated only by the bus bar isolating switch. If the conventional frequency-modulated series resonance voltage withstand test method is used in the AC voltage withstand test of the newly-built GIS while the original part is charged

because the test frequency is in the range of 30

1

00 Hz and the phases are not fixed

there must exists a moment at which the testing voltage and the running voltage overlaps to make the break voltage get maximum

resulting the isolating switch breakdown and GIS equipment in danger. To solve the problem

this study analyzed the isol

ating switch break voltage during test to find a way to reduce the break voltage

and hence improved the series resonance voltage withstand test method. Subsequently

an AC voltage withstand test method based on same-frequency same-phase principle was proposed

and the corresponding voltage withstand test device was developed. Field test verified the effectiveness and reliability of the proposed method and device. The proposed method realizes the AC voltage withstand test of newly-built GIS possible with the original part being charged

and enhances the reliability of power supply.