The relationship between dynamic stray current and noise

The stray current leaked from rail transit may invade the power supply system of the urban power grid and cause the DC bias of the transformer. In order to study the DC bias of the transformer caused by the dynamic stray current, it is necessary to carry out the field measurement and data analysis of the stray current. Based on the action mechanism of dynamic stray current on transformer DC bias, this paper uses a special open-coil type stray current sensor and an 8-channel vibration acceleration synchronous monitoring system to measure the stray current and the vibration acceleration of the transformer shell on-site. The numerical calculation of the DC bias current of the transformer caused by the stray current can measure the acceleration while measuring the stray current, so as to accurately calculate the neutral point of the transformer and the stray current of the outlet field. The analysis of the stray current data can effectively The effective spectral components of the stray current can be determined in a timely manner, which can provide reproducible basic data for the DC bias test of the transformer.

With the rapid growth of urban power transmission cable scale, the harmonic pollution in the high-voltage power grid is more transmitted to other power grids of different voltage levels, which makes the harmonic transmission more complicated, increases the harmonic emission level, and makes it difficult to quantitatively analyze and study the allowable value of users’ electrical pollution emission. Therefore, in this paper, by establishing the harmonic conduction model of the urban high-voltage power grid and considering the equivalent circuit of transformer and transmission cable in the urban power grid, the parameters of transmission cable harmonic transfer coefficient and the allowable emission value of power quality pollution of the urban power grid are deduced and quantitatively analyzed. Then the harmonic transmission and mutual influence of urban power network harmonics in power transmission cable are analyzed through examples, which is helpful to determine the allowable value of harmonic pollution emission scientifically and reasonably.

Urban grid planning needs to focus on sound investment plans to improve the safety and reliability of power system power supply to meet the growing needs of users. Does not adversely affect the environment. The contradiction in urban power grid and urban planning is an important reason that plagues the rapid development of power grid enterprises. Therefore, under the trend of urbanized dogs, urban power grid construction planning and urban overall planning are required to match. Urban planning needs to consider urban power grid planning as an important component, and match urban development to achieve simultaneous development. The integrated management and distribution system is the platform that contains all the information processing. It can share information and improve the reliability and security of the grid operation. This paper first introduces the integrated system of urban problems and its concept and architecture, focusing on the overall design form and process information management model, system function structure and several aspects of the main functions of the integrated system.

Urban power grid is a typical load center. According to the operational characteristics and structure of urban power grid, a complete set of urban grid operation risk index system where the calculation methods of each affiliated index is given, is proposed from the point of equipment direct loss, grid structure integrity failure, grid security margin and power grid load loss. On this basis, the paper makes use of Analytic Hierarchy Process (AHP) to synthesize the affiliated index and draw the total risk index of power system to assess the risk level of power grid. Taking the Polish power grid as an example, the paper calculates and analyzes each affiliated index and the total risk index based on a preset contingency, and verifies the feasibility of the proposed risk assessment index system and methods. And the indices computed are for use by operators and operational engineers in the control room to assess system security levels as a function of existing and near-future network conditions.

Shanghai is one of China's highest levels of industrialization and most economically developed regions. In the backdrop of the development of smart grid, smart electric power industry will be to play a very important position in the Shanghai urban area's electric power industry. This paper will focus on the analysis of the present situation of Shanghai urban area's power grid, especially the basic skills and business models of the power demand side. It is researched that the blueprint of the Shanghai urban area's future power grid and achieving methods based on the related smart electricity work carried on in the current Shanghai urban area and its effectiveness, especially, the pilot project. The main work is as follows: the description of the current Shanghai urban area power grid, including the history, development and evolution, load characteristics level, reliability, power distribution automation level and so on. The presented situation of smart power, which mainly includes the information collection system pilot project, electric vehicle charging facilities pilot project, intelligent building pilot project, flexible DC power transmission pilot project, the power FTTH (Fiber to The Home) to households pilot project, especially combine with the smart grid key pilot projects, such as the smart power design and practice of Shanghai World Expo smart grid pilot projects, and point out the current shortage and inadequate of the smart grid. The blueprint and achieving methods of the smart electricity describes the design blueprint of the future smart electricity in Shanghai urban area, and the means and direction to realize, such as to adapt and promote clean energy development, realizing highly smart grid dispatching to meet the electric vehicle and other new electricity consumers of electricity service requirements, efficient use and life cycle management of grid assets, convenient interaction between power users and grid, grid management informationalization and delicacy and playing the role of value-added services potential of the grid infrastructure.

Metropolitan Railways is a large-scale, extensively illustrated publication that deals with the growth and development of urban rail transit in North America. The history of rail transit technology from such impractical early schemes as a proposed steam-powered arcade railway under New York's Broadway through today's sophisticated systems are described in detail. Topics discussed in the publication include: (1) the quest for rapid transit; (2) the era of the elevated; (3) rapid transit goes underground; (4) rapid transit at mid-century -- new systems and a new era; (5) new metro technologies; (6) light rail transit - new life for an old technology; (7) conveyances for the multitudes - the cars we rode; (8) a metropolitan railways renaissance; (9) the technology of rail transit; and (10) North American metro and light rail transit.

Large-scale urban power grid is facing increasingly serious trend of heavy load problem. The cost of traditional solutions is usually high due to large investment and difficult implementation of urban construction. In this literature, the application of three types of power electronic technology in solving unbalanced power flow of urban power grid is considered. The technical theory of UPFC is analyzed for entry point. By comparing with flexible DC technology and SSSC which are of the same type with UPFC, the application scenarios of three types of power electronic devices are demonstrated and the feasibility of UPFC above flexible DC technology and SSSC in urban power grid are proposed. Then an actual problem of a real urban power grid and several solutions including UFPC are studied and compared, which shows the application potential of UPFC in project perspective.

With the rapid development of urban rail transit in various parts of China, the supply and demand contradiction between the commercial development level of rail transit integrated transfer hubs and passenger demand has become increasingly obvious, and it is of great significance to clarify the consumption characteristics and influencing factors of passengers from the rail transit integrated transfer hubs to solve the contradiction between supply and demand. In this paper, passengers of major rail transit integrated transfer hubs in Beijing and Tianjin are selected as samples, and combined with questionnaire survey and data statistics, the consumption characteristics of passengers at hub stations are quantitatively analyzed, and the influence mechanism of passengers' basic attributes and travel behavior on their consumption characteristics is studied. Through data processing, correlation analysis, regression analysis, and other analysis methods, five key factors affecting passenger consumption and the corresponding influence mechanism are obtained, respectively, and the regression model of five consumption characteristics is obtained, which lays a foundation for the optimization and improvement of the commercial layout of the integrated transfer hub of rail transit in the future.

Urban rail transit, as a green, environmentally friendly, safe, and efficient mode of transportation, plays a crucial role in urban sustainable development. However, the influencing mechanism of build environment factors on rail transit ridership still needs to be further investigated. Also, the interaction effects between these factors have not been considered. This study aims to explore the relationship and impact of built environmental factors on metro ridership. The research employs the Multiscale Geographically Weighted Regression (MGWR) model to analyze the temporal and spatial effects of built environmental factors on the rail transit ridership. The GeoDetector model is utilized to investigate the interactive effects of these factors on rail transit ridership. The Shanghai Metro ridership data and built environment data are applied to validate the model. Based on data analysis results, we found that Food & Beverages and Accommodation services, respectively, have the greatest impact on metro ridership on weekdays and weekends. Furthermore, the interaction effects between other variable and Land use diversity significantly enhance rail transit ridership, validating the promoting effect of land use diversity on metro ridership. By proposing recommendations for relevant urban planning and policy formulation, we can foster the sustainable development of urban rail transit.

Modern power grid has a fundamental role in the operation of smart cities. However, high impact low probability extreme events bring severe challenges to the security of urban power grid. With an increasing focus on these threats, the resilience of urban power grid has become a prior topic for a modern smart city. A resilient power grid can resist, adapt to, and timely recover from disruptions. It has four characteristics, namely anticipation, absorption, adaptation, and recovery. This paper aims to systematically investigate the development of resilient power grid for smart city. Firstly, this paper makes a review on the high impact low probability extreme events categories that influence power grid, which can be divided into extreme weather and natural disaster, human-made malicious attacks, and social crisis. Then, resilience evaluation frameworks and quantification metrics are discussed. In addition, various existing resilience enhancement strategies, which are based on microgrids, active distribution networks, integrated and multi energy systems, distributed energy resources and flexible resources, cyber-physical systems, and some resilience enhancement methods, including probabilistic forecasting and analysis, artificial intelligence driven methods, and other cutting-edge technologies are summarized. Finally, this paper presents some further possible directions and developments for urban power grid resilience research, which focus on power-electronized urban distribution network, flexible distributed resource aggregation, cyber-physical-social systems, multi-energy systems, intelligent electrical transportation and artificial intelligence and Big Data technology.

This paper puts forward the planning and configuration principle of the battery energy storage station(BESS) of the urban secure power grid, and establishes the full-life cycle economic model of the BESS based on the configuration requirements in urban secure power grid for the emergency power supply. Taking the maximum annual equivalent income as the objective function, an economic allocation model of the capacity of BESS for urban secure power grid based on improved particle swarm optimization algorithm(IPSO) was established to achieve the economic optimization of the capacity arrangement of energy storage power station while meeting the important load holding of the city under the disaster scenario of reliable support. At the same time, a reliability analysis model for energy storage capacity configuration results considering the impact of disasters is established to support the reasonable selection. Finally, the scheme comparison and optimization design are carried out based on the actual scenario of an urban secure power grid.

As an urban infrastructure, rail transit has the advantages of high efficiency, environmental protection, punctuality and dense stations, gradually becoming the backbone of urban public transport. However, in the construction and operation process, negative effects such as policy change, extended construction period, overdraft and quality defects have become key obstacles to the sustainable development of urban rail transit. Therefore, based on the analysis of China's national conditions and literature, this paper constructs a triangle-cone sustainable concept model for the policy-oriented PPP industry of urban rail transit, determining 4 dimensions and 17 evaluation indexes of sustainable evaluation. Finally, the stage analysis of urban rail transit sustainable development is carried out in the form of fishbone diagram, and its sustainable development is further considered from the perspective of the whole life cycle.

Under the background of the rapid development of urban rail transit in China, the development demand of urban underground space has also greatly increased especially in the rail transit station areas. In this paper, taking the high-speed railway station area of Xuzhou Metro Line 1 as an example, the underground space development demand evaluation is conducted by considering the principle of urban underground space stock planning, the local underground space development conditions, as well as the special planning of the local urban constructions. Using the Analytic Hierarchy Process (AHP), a specific weight indicator scale is employed after the rationality of different weight indicator scales being compared. And then the weight indicator of different function types, i.e., commercial, parking, road, etc., are calculated and laterly utilized to forecast the recent development demand of underground space in the station area. Moreover, the steps to forecast the underground space development demand in rail transit station area are proposed, which can provide a reference for the forecasting of underground space development demand in the urban rail transit station areas.

Following the rapid development of urban rail transit, networking operation will be an inevitable trend for rail transit. How to formulate reasonable train dispatching program and achieve total optimal efficiency has become the key issue to be addressed. The cross-line operation of the subway can effectively reduce the transfer station pressure and improve the service quality. This paper studies the train schedule optimization problem under the cross-line operation mode for a subway network, where the time-dependent passengers demand is considered. A mixed integer linear optimization (MILP) model is formulated with the objective of minimizing the passengers travel times and train operating costs. A genetic algorithm (GA) is designed to obtain high-quality solutions. The computational results illustrate that adopting cross-line operation can reduce the total travel time of passengers by 49.3% and train operating costs by 62.5%.

External tie line power fluctuations smoothing strategy of new urban power grid