With the development of strong and smart grid, power grid and communication system become highly interconnected and mutually dependent. Complex network approach is applied in this paper to describe the interactive characteristics of hybrid power and communication systems in terms of topologies. Qualitative analysis of the impact of communication system on power grid is straightforward. However, quantitative analysis is challenge. This paper proposes a generic and systematic approach for quantitatively studying the impact of communication failures on power control system's measurement and control functions.