Internal fuse is an important protective device against inter-electrode short-circuit of high voltage capacitor. However

no reliable method can be used in internal fuse analysis and selection. Currently

the parameters of the internal fuse are determined according to field experience. To solve the parameters selection problem of capacitor internal fuse

according to equivalent electrical circuits of a broken-down capacitor element and the second order circuit theory

the transient current flowed through broken-down device and the energy injected into internal fuse series connected with the capacitor are derived and given when the capacitor unit is broken-down. Taking BAM6.56-556-1W capacitor for UHV project as example

we carried out theoretical calculation

simulation and verification test

and the calculation

simulation and experimental results are consistent. The results can solve the internal fuse parameters selection problem of high voltage capacitor which can be taken as a reference to capacitor internal fuse design.