Based on the integer linear programming formulation proposed for optimal PMU placement, this paper presents a generalized integer linear programming formulation for cases including redundant PMU placement, full observability and incomplete observability. Due to accurate voltage phasor measurement and current phasor measurements provided by PUM units, the accuracy, redundancy and thus the robustness of state estimation will be enhanced with the integration of PMU measurements. The problem of optimal placement of PMU for the redundant PMU placement, full observability and incomplete observability analysis needs to be studied, for various purposes and considerations. The proposed modeling approach by the author in another paper, which models PMU placement as an integer linear programming problem, is extended and generalized to satisfy different needs. Cases with and without zero injection measurements are considered. Simulation results on different power systems show that the proposed algorithm can be used in practice.