Cyber system plays an important role in supervising and controlling power system. Besides its contribution of much convenience to power industry, the cyber system brings some potential danger because of its inherent vulnerability. It is significant to assess the vulnerability of cyber system, determine its risk to power industry, find out the weak parts, set appropriate response to the probable accidents and enhance the safety of the cyber system. By analyzing the threats and vulnerability of cyber system in detail, mainly including the vulnerability of SCADA (Supervisory Control and Data Acquisition) system, EMS (Energy Management System) and MIS (Management Information Systems), this paper proposes two methods, the probabilistic assessment and the integrated risk assessment, to assess the cyber security vulnerability. And some ways are suggested to promote the security of cyber system in power industry.
