Impacts of Time Delay and False Data Injection Attacks on Power System Control Loops

Abstract

Modern power grid is one of the largest cyber-physical infrastructure seen in our daily life. Wide-Area Monitoring, Protection and Control System (WAMPCS) ensures that the power grid operates in a stable condition by allowing real-time remote control and measurement over the power grid. Apart from this, WAMPCS, because of the extensive use of IT infrastructure exposes the system to potential cyber attacks. In this thesis, impacts of some of these attacks; time delay attack (TDA), false data injection attack (FDA) on the frequency and voltage control loops are analyzed. To analyze the effects on frequency control loop an identical 2 area tie-line system is considered. The characteristic equation of the system under TDA is used, to determine the optimum value of delay that brings the system to marginal stability. Similarly, the range of FDA proportional constant (?), that keeps the system in stable condition is determined using the characteristic equation of the system under FDA. Likewise, the effects on voltage are studied on an IEEE excitation loop which comprises the basic components for terminal voltage control in a generator excitation system. An analysis similar to the frequency control loop is made and the characteristic equations for the system under the two attacks are developed. Optimum values for the time delay and the range of FDA proportional constant (?) for the system stability are obtained. Results have shown that the system does not go into instability if the attack parameters values lie in the determined range. Any value other than that moves the system towards instability. Also, it is observed that in either control loops a combined attack is more powerful than when an attack is launched individually. Considering the effect of power market on system performance, mitigation strategies for the attacks can be integral parts of future work to improve protection for the power system.