Vulnerability analysis of power grid with the network science approach based on actual grid characteristics: A case study in Iran
Introduction
Power grid is one of the most vital infrastructures of any country, and due to the dependency of a whole nation on this public utility, utmost reliability and constant availability of power supply is a basic necessity. Power grid topology refers to the network of high-voltage transmission lines that transmit electricity over long distances within and between countries. The vertices of aforementioned network are the generators and substations and its edges are high-voltage lines. While all transmission substations are important components of power grid, position and operating condition of some substations make them more essential for network stability, which in turn make their reliability, safety, and security all the more imperative. In this context, the term vulnerability analysis refers to the process of identifying key substations and evaluating their role in the reliability of electricity grid [1].
Two important aspects of power grid vulnerability analysis are: network topology and network operating condition. Network topology is concerned with how its components are connected while network operating condition deals with how the load is distributed over the grid. Network topology is essentially static while operating condition is dynamic and in constant change depending on grid characteristics such as peak load.
The majority of published works on power grid vulnerability analysis that employ the network science approach have focused on network topology and paid little attention to weights and directions of its components [2]. In the few cases where direction is taken into account, lack of attention to core characteristics of a power grid, namely line load and line failure rate, have made the results inconsistent with network reality.
In this paper, we first introduce a novel power grid vulnerability prediction method and then use this method both to analyze the condition, structure and vulnerabilities of Iran’s 400 kV and 230 kV power grids and to predict their vulnerabilities at different time horizons.
The following section, firstly, the literature on power grid analysis that is based on the network science is reviewed. Secondly, weighted power grid is considered based on the proposed method and identify power grid vulnerabilities by taking both network topology and grid characteristics. In the next section, the proposed method is applied for a fragment of Iranian power grids at 400 kV and 230 kV, and the results are evaluated against those obtained by engineers at the dispatching centers.
Section snippets
Power grid analysis based on the network science
In recent years, power grid vulnerabilities have received increasing attention from researchers in the field of complex networks and have been a topic of immense research. For example, vulnerabilities of US power grid were studied by Albert [1] (2004), Chassin (2005) [2], Wang (2009) [3], Hines (2010) [4], and Xu (2014) [5], and those of European power grid were explored by Rosas-Casals [6], [7], [8], [9] (2007–2010). This same concern in Italy was investigated by Crucittia (2004) [10], Bompard
The proposed method
The proposed method aims to identify power grid vulnerabilities by taking both network topology and grid characteristics (line loads and failure rates) into account simultaneously.
Network topology is determined by taking a snapshot of power grid at peak hours, which reflects the network behavior and thus vulnerabilities under worst case scenario. Network topology calculations are carried out using a slightly modified version of Weighted PageRank (WPR) algorithm. Shams and Khansari [30] have
Implementation of the proposed method on a section of Iranian power grid
The proposed method was tested on a section of Iranian power grid with 68 substations (nodes) and 98 transmission lines (edges). Data pertaining to this grid was gathered from the official site of Iran Grid Management Company (www.igmc.ir). After importing the data into the software Pajek [33], the diagram of this directed network under peak load was obtained as shown in Fig. 3.
Utilizing the proposed model required reliability calculations for each transmission line. The reliability
Conclusion
Transmission substations are all key components of power grids, however, due to particular location and operating conditions of some substations within the network, which affects power grid’s stability, these substations are attended with relatively higher sensitivity and their reliability is of more concern than their counterparts. A survey of previous studies on power grid vulnerability analysis that is based on the network science deal with power grids as unweighted and undirected graph,
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