The time-varying topological structure

device and state diversity and random fuzziness and the self-healing ability of the active distribution network have brought new operational risks and challenges to the safety of the power grid. As methods of traditional analysis of the power system can hardly satisfy the demand of active distribution network

a new method is badly needed for assessment of active distribution network's operational risks and providing operational advice for automation system and dispatchers. Based on the complex network theory and the features of active distribution network

a rapid and multi-level operational risk assessment system capable for real-time risk warning and multistage risk analysis is proposed

which allows for sufficient time to make appropriate operational decisions and real-time protection of the power grid. On the premise of the active distribution automation system and some advanced mathematical tools such as the credibility theory

the system proposed can rapidly respond to the change of network structure and components

including the controllable loads

electric cars

distributed generators and energy storage devices. Qualitative and quantitative multistage operation risk assessment results are given to assist dispatchers to reduce the risks of system and prevent large area blackout. Finally

an example is given to illustrate the feasibility

rapidity

flexibility

practicality and applicability of the operational risk assessment system. This work is supported by National High Technology Research and Development Program of China(863 Program)(No. 2014AA051901).