The operation mechanism and equivalent circuit of a capacitor voltage transformer（CVT） are investigated for analyzing the frequent blow of a 35 kV CVT high-voltage fuse protector.By volt-ampere characteristic test of a medium voltage CVT

it is found that the core of medium voltage CVT is saturated deeply to excite ferromagnetic resonance

which leads to the high-voltage fuse protector blow

during the transition process of single-phase grounding failure or failure elimination.And then

an available method for ferromagnetic resonance inhibition is proposed

in which a damper is paralleled to the secondary residual winding in the medium voltage CVT.Moreover

it is necessary to improve non-load magnetization characteristic of medium voltage transformer and choose the one with superior volt-ampere characteristic in design and manufacture process.