  Power systems often rely on natural gas pipeline networks to supply fuel for
gas-fired generation. Market inefficiencies and a lack of formal coordination
between the wholesale power and gas delivery infrastructures may magnify the
broader impact of a cyber-attack on a natural gas pipeline. In this study we
present a model that can be used to quantify the impact of cyber-attacks on
electricity and gas delivery operations. We model activation of cyber-attack
vectors that attempt to gain access to pipeline gas compressor controls using a
continuous-time Markov chain over a state space based on the gas operator
Industrial Control System firewall zone partition. Our approach evaluates the
operating states and decision-making in the networks using physically realistic
and operationally representative models. We summarize these models, the
sequence of analyses used to quantify the impacts of a cyber-incident, and
propose a Monte Carlo simulation approach to quantify the resulting effect on
the reliability of the bulk power system by the increase in operational cost.
The methodology is applied to a case study of interacting power, gas, and cyber
test networks.
