Cascading Failures In Power Grids Research Articles

The interplay of network structure and dispatch solutions in power grid cascading failures.

For a given minimum cost of the electricity dispatch, multiple equivalent dispatch solutions may exist. We explore the sensitivity of networks to these dispatch solutions and their impact on the vulnerability of the network to cascading failure blackouts. It is shown that, depending on the heterogeneity of the network structure, the blackout statistics can be sensitive to the dispatch solution chosen, with the clustering coefficient of the network being a key ingredient. We also investigate mechanisms or configurations that decrease discrepancies that can occur between the different dispatch solutions.

Cascading failures in ac electricity grids.

Sudden failure of a single transmission element in a power grid can induce a domino effect of cascading failures, which can lead to the isolation of a large number of consumers or even to the failure of the entire grid. Here we present results of the simulation of cascading failures in power grids, using an alternating current (AC) model. We first apply this model to a regular square grid topology. For a random placement of consumers and generators on the grid, the probability to find more than a certain number of unsupplied consumers decays as a power law and obeys a scaling law with respect to system size. Varying the transmitted power threshold above which a transmission line fails does not seem to change the power-law exponent q≈1.6. Furthermore, we study the influence of the placement of generators and consumers on the number of affected consumers and demonstrate that large clusters of generators and consumers are especially vulnerable to cascading failures. As a real-world topology, we consider the German high-voltage transmission grid. Applying the dynamic AC model and considering a random placement of consumers, we find that the probability to disconnect more than a certain number of consumers depends strongly on the threshold. For large thresholds the decay is clearly exponential, while for small ones the decay is slow, indicating a power-law decay.

A topological investigation of phase transitions of cascading failures in power grids

Cascading failures are one of the main reasons for blackouts in electric power transmission grids. The economic cost of such failures is in the order of tens of billion dollars annually. The loading level of power system is a key aspect to determine the amount of the damage caused by cascading failures. Existing studies show that the blackout size exhibits phase transitions as the loading level increases. This paper investigates the impact of the topology of a power grid on phase transitions in its robustness. Three spectral graph metrics are considered: spectral radius, effective graph resistance and algebraic connectivity. Experimental results from a model of cascading failures in power grids on the IEEE power systems demonstrate the applicability of these metrics to design/optimise a power grid topology for an enhanced phase transition behaviour of the system.

Risk Assessment of Cascading Failures in Power System Based on Fuzzy Theory

This paper makes a grading of the probability of cascading failures using the theory of fuzzy C-means clustering to implement the level of risk assessment. Then from the perspective of power system transient security, use the specific severity functions to grade the probability of cascading failures, and the synthetical severity is graded by fuzzy theory. Finally, synthesizing the probability of cascading failures with the severity of failure, and the level of risk assessment is determined according to the principle of the maximum membership. Finally, taking IEEE 39 system for example, to assess the level of the risk of cascading failures in power grid, thus the rationality and effectiveness of the proposed algorithm are verified.

Cancer develops, progresses and responds to therapies through restricted perturbation of the protein-protein interaction network.

The products of genes mutated or differentially expressed in cancer tend to occupy central positions within the network of protein-protein interactions, or the interactome network. Integration of different types of gene and protein relationships has considerably increased the understanding of the mechanisms of carcinogenesis, while also enhancing the applicability of expression signatures. In this scenario, however, it remains unknown how cancer develops, progresses and responds to therapies in a potentially controlled manner at the systems level. Here, by applying the concepts of load transfer and cascading failures in power grids, we examine the impact and transmission of cancer-related gene expression changes in the interactome network. Relative to random perturbations, this study reveals topological robustness associated with all cancer conditions. In addition, experimental perturbation of a central cancer node, which consists of over-expression of the α-synuclein (SNCA) protein in MCF7 breast cancer cells, also reveals robustness. Conversely, a search for proteins with an opposite topological impact identifies the autophagy pathway. Mechanistically, the existence of smaller shortest paths among cancer-related proteins appears to be a topological feature that partially contributes to the restricted perturbation of the network. Together, the results of this study suggest that cancer develops, progresses and responds to therapies following controlled, restricted perturbation of the interactome network.

Vulnerability Assessment Scheme for Power System Transmission Networks Based on the Fault Chain Theory

Vulnerable transmission lines or sections have great impacts on large-scale blackouts and cascading failures in power grids. A comprehensive scheme to study transmission vulnerability based on the fault chain theory of security science is proposed in this paper. In this scheme, the cascading failure process and its generic features are described according to a fault chain. Power flow transfer, sequent overload of lines, and damage of transmission sections are modeled and normalized to predict all the fault chains. On the basis of the fault chains, a new vulnerability assessment index is presented to identify critical lines and sections contributing to failure extension and system instability. The effectiveness of the proposed assessment scheme is demonstrated via numerical examples on three power systems. Considering operation properties and transient impact, the proposed scheme can be executed in an efficient way.

Reciprocally altruistic agents for the mitigation of cascading failures in power grids

Cascading failures in electrical power networks often come with disastrous consequences. A variety of schemes for mitigating cascading failures exist, but the vast majority depend upon centralised control architectures. Centralised designs are frequently more susceptible to communications latency and bandwidth limitations and can be vulnerable to random failures and directed attacks. This paper proposes a decentralised approach. We place control agents at each substation in a power network, each of which uses decentralised Model Predictive Control (MPC) to select emergency control actions. When making decisions, the control agents consider not only their own goals, but also the goals of nearby agents. Thus the agents act with Reciprocal Altruism (RA). Results from simulations of extreme cascading failures within the IEEE 300 bus test network indicate that this approach can dramatically reduce the average size and social cost of large cascading failures. Simulations also show that the bandwidth required for message passing is well within the limits of current technology.