Generation outages, transmission line contingencies, natural gas pipeline contingencies, compressor failures as well as gas source and load fluctuation are posing a great threat to the secure operation of a combined natural gas system and power system(CGPS). To quantify the risk level caused by these dangerous factors, this paper proposes a generalized CGPS risk assessment model, in which the modeling of linepack of pipeline and gas tank are taking into account. Besides, by calculating the specific electricity and gas load loss utilizing a state-based non-sequential Monte Carlo method, the effects of linepack and gas storage tank on improving the whole reliability level of the CGPS can be quantitatively assessed. Finally, the evaluation model is validated by a combined 6-node electricity network and 14-node gas network test case. The results show that the proposed model can effectively assess the influence of those uncertainties on the combined system risk level, and the contribution of linepack and gas storage tank on the resilience of the integrated system can also be quantitative calculated by given indicators.

combined natural gas system and power system; gas storage tank; linepack; risk assessment