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Identifying and preferentially reinforcing critical lines for skeleton-network of power systems is significant in improving the secure and stable operation of power systems under extreme weather conditions. Under this background, in this paper, six indexes are first presented for identifying critical lines for skeleton-network with the power elements' parameters and the impact of extreme weather conditions, the network topology and the operation state of power systems considered. Then, the modified Vise Kriterijumska Optimizacija I Kompromisno Resenje in Serbian (VIKOR) method, in which the synthetic weights of indexes determined by the combination weighting method are adopted, is utilized to identify the importance degrees of lines in a given power system. Both the overall performance and the outstanding individual performance of lines are considered, which is beneficial for the critical lines identification for skeleton-network. Finally, the proposed multi-indexes and methods are applied to part of the actual Guangdong power system in China. The numerical results are compared with those obtained by single-attribute and multi-attribute evaluation methods and other evaluation methods.

The ongoing energy transition requires power grid extensions to connect renewable generators to consumers and to transfer power among distant areas. The process of grid extension requires a large investment of resources and is supposed to make grid operation more robust. Yet, counter-intuitively, increasing the capacity of existing lines or adding new lines may also reduce the overall system performance and even promote blackouts due to Braess’ paradox. Braess’ paradox was theoretically modeled but not yet proven in realistically scaled power grids. Here, we present an experimental setup demonstrating Braess’ paradox in an AC power grid and show how it constrains ongoing large-scale grid extension projects. We present a topological theory that reveals the key mechanism and predicts Braessian grid extensions from the network structure. These results offer a theoretical method to understand and practical guidelines in support of preventing unsuitable infrastructures and the systemic planning of grid extensions.

Data of modern AC/DC hybrid power grid has become more and more complex with the dramatically extended volume because of the significant development of the technology of information acquisition and data processing during the past few decades. It will be of importance for the control and operation of power grid by using new methods to analyze the more enriched and disparate data. In this paper, Neo4j, one of the most outstanding graph databases in the world, is used to integrate the data related with lighting and failure information from different enterprise application system (EAPs). With the help of high-performance network topology algorithms provided by Neo4j, conventional failure rate of transmission line can be further divided into two different failure rates corresponding to the lightning region and non-lightning region, while the relationship between the lightning information and the failure rate of transmission lines can be drawn more clearly by comparing the two types of failure rates. The conclusion is validated in a real large-scale regional grid at the end of this paper.Index Terms-power system data, graph database, data analysis, failure rate of transmission line MA Yisong received the undergraduate degree from South China University of Technology, Guangdong, China, in 2013. He is currently working toward the M.S. degree at

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The AT (Auto Transformer) power mode with parallel connection is applied on dedicated passenger lines in China on a large scale. In the power supply mode, the traction transformer is single phase with mid-point connected to the ground in its secondary side. High manufacturing cost is the shortage of this type of transformer. A new AT power supply mode was brought forward in [1]. The traction transformer is single phase without mid-point connected to the ground in its secondary side Based on the characteristic of this power supply mode and generalized method of symmetrical components (GMSC), the short circuit impedance was analyzed. The impedance characteristic of single line and double lines running mode were shown as impedance-distance curve. According to the curve, it show research on fault location of this type of power supply mode is needed.

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