Cyber-physical attacks and defences in the smart grid: a survey <s> Generation system attacks <s> This paper addresses the attack modeling using vulnerability of information, communication and electric grid network. Vulnerability of electric grid with incomplete information has been analyzed using graph theory based approach. Vulnerability of information and communication (cyber) network has been modeled utilizing concepts of discovery, access, feasibility, communication speed and detection threat. Common attack vector based on vulnerability of cyber and physical system have been utilized to operate breakers associated with generating resources to model aurora-like event. Real time simulations for modified IEEE 14 bus test case system and graph theory analysis for IEEE 118 bus system have been presented. Test case results show the possible impact on smart grid caused by integrated cyber-physical attack. <s> BIB001 </s> Cyber-physical attacks and defences in the smart grid: a survey <s> Generation system attacks <s> While open communication infrastructures are embedded into smart grids to support vast amounts of data exchange, it makes smart grids vulnerable to cyber attacks. In this paper, we investigate the effects of Denial-of-Service (DoS) attacks on load frequency control (LFC) of smart grids. In contrast with existing works, we consider the problem that how DoS attacks affect the dynamic performance of a power system. The state space model of power systems under DoS attacks is formulated as a switched system. By applying switched system theories, the existence of DoS attacks that make the dynamics of a power system unstable is proved. A two-area power system is used to conduct case studies. The dynamic performance of the power system, such as convergence and steady-state errors, is compared under different DoS attack scenarios. It is shown that the dynamic performance of the power system is affected strongly if the adversaries launch DoS attacks before the dynamics of the power system converge. <s> BIB002 </s> Cyber-physical attacks and defences in the smart grid: a survey <s> Generation system attacks <s> Cyber systems play a critical role in improving the efficiency and reliability of power system operation and ensuring the system remains within safe operating margins. An adversary can inflict severe damage to the underlying physical system by compromising the control and monitoring applications facilitated by the cyber layer. Protection of critical assets from electronic threats has traditionally been done through conventional cyber security measures that involve host-based and network-based security technologies. However, it has been recognized that highly skilled attacks can bypass these security mechanisms to disrupt the smooth operation of control systems. There is a growing need for cyber-attack-resilient control techniques that look beyond traditional cyber defense mechanisms to detect highly skilled attacks. In this paper, we make the following contributions. We first demonstrate the impact of data integrity attacks on Automatic Generation Control (AGC) on power system frequency and electricity market operation. We propose a general framework to the application of attack resilient control to power systems as a composition of smart attack detection and mitigation. Finally, we develop a model-based anomaly detection and attack mitigation algorithm for AGC. We evaluate the detection capability of the proposed anomaly detection algorithm through simulation studies. Our results show that the algorithm is capable of detecting scaling and ramp attacks with low false positive and negative rates. The proposed model-based mitigation algorithm is also efficient in maintaining system frequency within acceptable limits during the attack period. <s> BIB003 </s> Cyber-physical attacks and defences in the smart grid: a survey <s> Generation system attacks <s> Current smart power grids have open communication infrastructures to improve efficiency, reliability and sustainability of supply. However, their open communication architecture makes them vulnerable to cyber-attacks with potentially catastrophic consequences. Here for the first time, we propose a time-delay-switch (TDS) attack by introducing time delays in the dynamics of power systems. Such an attack will have devastating consequences on smart grids if no prevention measures are considered in the design of these power systems. We considered how a TDS attack affects the dynamic performance of a power system. To do this, we first formulated a state space model of a smart power grid system under TDS attack using a hybrid systems approach. Second, we prove by analysis and demonstrate by simulation examples how a TDS attack can be used to sabotage and destabilize a smart grid. <s> BIB004
Interconnected power systems are managed by corresponding control areas, among which redundant power generated in one area flow along the tie-lines into another. The power generation in each control area is required to meet the dynamic load demand and the net interchanges so the load-generation balance can be maintained. To this end, the AGC has been widely implemented in modern generation systems. A functional diagram of the AGC is illustrated in Fig. 3 . An AGC system consists of two major functions: (i) the load-frequency control (LFC) that maintains the load-generation power balance and system frequency; (ii) the ED that distributes the generation among generators with minimal operating costs subject to stability and security constraints. Since ED does not directly issue control commands to the system, we will focus on the LFC-related attack schemes herein. The LFC uses a primary controller to govern turbine speeds and adjust the generator outputs. In addition, a supplementary/ secondary controller is employed to maintain system frequency based on the area control error (ACE). The ACE is obtained as a function of inter-area power interchanges DP TL and system frequency deviations Df where b is a scale factor. In normal operations, the value of ACE in each control area should be minimised toward zero. The Aurora attack is a test scheme that exploits the vulnerability in the primary controller of AGC  . In the original test conducted by the Idaho National Lab, an assumed cyber-attacker applies fast opening and closure of the circuit breakers of a generator. When the actions are conducted within a critical time window, the generator became desynchronised and was ultimately destroyed. The impacts of the Aurora attack range from a short-term power outage to a long-term generation deficiency. An Aurora-like CP attack with incomplete information of the power system has been subsequently developed BIB001 . CP attacks on the input of secondary controller have also demonstrated feasible impacts on power system frequency stability. Four typical manipulations on the AGC input, i.e. scaling, ramping, pulse, and random attack, have been investigated in BIB003 . The investigation has demonstrated that the attacked inputs have effectively misled the LFC to incorrectly perform under-frequency load shedding in response to a fake frequency deviation. In addition, a malicious attacker can also induce substantial instability in the generation system by exerting significant loss BIB002 or delay BIB004 24] of the measurement packets sent to the AGC. A reachability analysis has revealed that malicious control signals sent by the LFC will cause inter-area power swinging in the system  . The swinging will mislead protective relays to trip generation units from the grid, leading to power shortages and/or outages as in the Aurora attack. Further investigation has proposed a malicious control policy that is robust against incomplete information and model uncertainty [26] : the incomplete information can be addressed by Markov chain Monte Carlo simulations and the model uncertainty is addressed by the feedback linearisation.