Sensitivity analysis of smart grids reliability due to indirect cyber-power interdependencies under various DG technologies, DG penetrations, and operation times

The cyber failures such as failures in protection and monitoring systems will not stop the operation or change the behavior of the power system instantly but will adversely affect the performance of the power system against the potential failure. Such indirect cyber-power interdependencies (ICPIs) may either intensify the probability of future failures or postpone the repercussion to the present failure of the power elements. The much less effort has been devoted in literature to investigate the ICPIs impacts, particularly in stochastic simulating space. In this paper, a novel stochastic-based reliability evaluation method which considers the ICPIs impacts under various uncertain parameters is proposed. The consideration of uncertainty regarding the renewable distributed generation (DG) units, consumption patterns, power and cyber elements, and ICPIs is one of the most important contributions of the proposed method. Further, a novel stochastic-based state upgrading is introduced to concern the ICPIs of protection and monitoring systems. By using the proposed state upgrading methodology, it is possible to evaluate the reliability of smart grid based on ICPIs by using conventional reliability evaluation methods. The proposed risk assessment methodology is applied to an actual distribution grid. The several sensitivity studies are performed to gain insight into how the penetration level of DG units under various DG technology scenarios can affect the ICPIs impacts on the risk level of smart grid. The test results show that regardless of the DG technology scenario, the ICPIs impacts of protection system vulnerabilities gradually increase while the DG penetration increases. On the contrary, the ICPIs impacts which are corresponding to the monitoring system monotonically decrease as a function of DG penetrations, and it saturates when the penetration exceeds a certain level. The test result infers that the ICPIs impacts on the risk level of smart grid are more dramatically emphasized when the extended study duration is analyzed. In fact, the ICPIs impacts increase as a function of system age, because the failure in monitoring system may accelerate the aging failures, and particularly when the system is subject to wear out period, the ICPIs impacts on the system reliability should be more concerned. (C) 2015 Elsevier Ltd. All rights reserved.