Some components in a power system are more vulnerable than others. Limited by the capability of the existing quasi-steady-state (QSS) models of cascading failures, previous analysis on vulnerable components typically omits the influence of voltage collapse. In this paper, we identify the nodes that are most susceptible to voltage collapse in cascading failures with a QSS model that applies practical measures in response to voltage collapse, i.e., undervoltage load shedding (UVLS) and protection relays. The proposed model is based on the continuation power flow (CPF). We apply the model to the IEEE 118-bus system, the IEEE 300-bus system, and the Polish 2383 bus system. We count the times and plot the locations of buses that exhibit a voltage collapse event in the network to assess structural vulnerability. Numerical results show that some parts of the network are more vulnerable to voltage collapse events than others.