The seismic performance assessment result of a single device in the power distribution system is difficult to characterize the overall seismic performance of the power distribution system and research on seismic safety assessment of high-voltage power distribution systems urgently needs to be developed. At present

the boundary estimation method for structural system reliability assessment has been applied and promoted in the field of civil engineering structures

but the application of this method in the probabilistic assessment of seismic performance of power system is less. Based on this

one high-voltage power distribution system of a certain actual project is taken as an example

the vulnerability of the distribution system by using the first-order boundary estimation method and the second-order boundary estimation method is studied. The study results show that the overrun probability of the distribution system is greater than that of any single device in the system; The boundary range of distribution system vulnerability curve solved by the first-order boundary estimation method is wide

which is not conducive to practical application of engineering; The boundary range of the vulnerability curve solved by the second-order boundary estimation method is narrow

but the lower bound is sensitive to the over-limit arrangement order of single devices in the system

so special attention should be paid when applying this method.