The contingency analysis of power systems represents a critical part of security monitoring, required to maintain power system reliability. In general, traditional N-1 contingency analysis methods simulate a few outages, due to the high computational costs involved. Thus, they may fail to identify some critical contingencies that can lead to cascading failures. This paper proposes a new approach to N-1 contingency analysis of electric transmission systems, based on network centrality measures. The proposed method evaluates all possible transmission line outages in a very short computational time, and it requires only topological information. Results are shown for two electric power systems: ITAIPU 11 bus and IEEE 39 bus. Comparisons between the results obtained by the proposed method and traditional ones show the accuracy of the proposed method to identify critical buses and transmission lines, in local and global context, even in absence of electrical information. The proposed method is interesting as a direct and fast tool applied to the pre-analysis process, since topological network behavior is verified. Thus, pre-analysis provides a prior response to the system operator of the points by which the electrical power system analysis should begin, in order to ensure safe operational state of the system.

Network performance optimization is a poly-parametric task where usually the physical network topology is already provided and given. The latter is mainly defined by the geographical needs and the business models developed in a region that reflect the particular data traffic requirements. However, during the design of a new network, the physical topology can be considered as an additional parameter, and this work aims to study the potential impact of a network topology in the performance of the network. Two relevant metrics of optical WDM networks are evaluated, throughput and blocking ratio. Through the simulation of 350k implementations of more than 500 network topologies, we demonstrate a performance variation on networks with the same number of nodes and edges up to 73.9% on the total network load under same levels of requests blocking ratio, and up to 17.3% on the network throughput.

Due to the increase of bandwidth supported by optical transport networks, it becomes important to identify how reliable the actual real-world network topologies are, and the relationship of reliability with other key factors. Reliability is essential in this context, since the failure of elements such as fiber links and cross connects may cause the outage of several associated optical channels, leading to large data losses. Here we address reliability related to link failures. For a fixed number of nodes, the maximum network reliability could be obtained by maximizing the number of links, but it is prohibitive due to the technological and cost constraints. However, for a given number of nodes and links, there exist a number of topologies that may have different levels of reliability. How can we build the most reliable topologies satisfying these constraints? How reliable are the real-world topologies? In order to answer these questions, we explore a class of topologies that maximize reliability. Such topologies correspond to a subclass of Harary graphs. In this paper, we compare the reliability of the real-world topologies to the most reliable ones. Also, we compare both sets of topologies with respect to cost. Our results show that, in some cases, after maximizing reliability, the resulting topologies may also present lower capital expenditure.