The short-time multiple faults occurring in a power grid in a weather disaster may exceed the preset reaction ability of the protection system, and the coupling effect of primary and secondary equipment will promote the development and spread of multiple fault risk. Thus this paper proposes a short-time risk assessment method considering the coupled faults of primary and secondary equipment. First, the interaction between primary and secondary equipment and its impact on the short-time operational risk of the power grid are analyzed. Second, the fault probability model of primary and secondary equipment is constructed, especially focusing on the failure-to-trip probability of protection with regard to coupled faults of primary and secondary equipment. Then, combined with the reaction ability of the protection system to unexpected faults, a short-time multi-fault risk assessment method is proposed. Finally, the proposed method is validated using a modified IEEE39-node system. The results show that, under the influence of external meteorological environment, unexpected actions caused by the exposure of defects in the protection system make the multiple fault risk in the grid more serious. This comprehensive consideration of short-time operational risk can be useful for identifying and eliminating weak points in protection systems and formulating risk-reduction operational strategies for power grids.