A simplified linearized dynamic model for fast assessment of voltage collapse is developed in this paper. The simplification was made under assumption that the voltages at generator nodes are constant, which means that only power changes at load nodes are considered in analysis. Dimensions of the state matrix, which eigenvalues are used for voltage collapse assessment, decrease under this assumption. Appropriate transformations of linearized state matrix prove that knowledge of values of the dynamical load change time constants is not required for this model.