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Li Z.,Huazhong University of Science and Technology | Lin X.,Huazhong University of Science and Technology | Lin X.,China Three Gorges University | Weng H.,China Yangtze Power Co. | Bo Z.,AREVA
IEEE Transactions on Power Delivery | Year: 2012

Existing superimposed-based distance protection possibly maloperates due to some extreme conditions, for instance, an external earth fault occurring while the transmission system operates at a large phase difference between the sources at two sides of the protected line. To solve this problem, an adaptive distance relay using the superimposed component and the information of the opposite end is put forward. The shortages of the existing schemes are first investigated, and the scenarios leading to the maloperations of those schemes in theory are clarified. Furthermore, corresponding countermeasures by means of the floating threshold and criterion switching are introduced. In this case, the reliability and the sensitivity of the superimposed-based distance protection are improved. By means of a variety of comprehensive tests, the feasibility of the proposed scheme is verified. © 2006 IEEE. Source


Zhou M.,Chongqing Three Gorges University | Xu T.,China Yangtze Power Co.
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2014

Since 2003 when the Three Gorges Reservoir started impounding, the regulation conditions have been changed significantly from the preliminary design, such as construction of a number of large and medium-sized hydropower stations in the upper reaches, continuous improvement on hydro-meteorological forecasting, and increased demands of reservoir dispatching in various aspects. To adapt to the new environment, from 2009 to 2012 this reservoir adopted optimized regulations such as impounding water in advance, improved control on small and medium-size floods, and floating on flood limited water level, so that its comprehensive benefits in flood control, power generation, navigation and water supply have been greatly improved. Simultaneously, ecological regulation that is practiced to promote fish breeding, expands the ecological benefit; and optimized sediment regulations are implemented, so the reservoir can remain for a long time with effective storage capacity. In addition, measures of increasing anchorage stations upstream and downstream to the Three Gorges ship lock and its rapid repair techniques are put into effect, which effectively improved its navigation capacity. © Copyright. Source


Xie R.,Hohai University | Pang Y.,Hohai University | Li Z.,China Yangtze Power Co. | Zhang N.,Jiangsu Provincial Environmental Monitoring Center | Hu F.,Hohai University
Environmental Management | Year: 2013

Eco-compensation is a multi-disciplinary topic. There is no consensus on the issue of river eco-compensation across districts. Although policies regarding river eco-compensation have been issued in China since 2008, due to the high cost, eco-compensation has not been well implemented in the Taihu pilot region. Therefore, a simplified method based solely on water quality (both water quality and water volume included in the Taihu method) was proposed for North Jiangsu province (NJP). However, the formula was flawed and it led to payments being too low. Three problems need to be solved: (1) how to specify the eco-compensation areas; (2) how to test a reasonable eco-compensation model and (3) how to determine the compensation criterion. Solving these issues is already a priority. In this paper, three potential solutions surrounding eco-compensation are discussed: (1) three principles for selecting the representative eco-compensation areas are suggested; (2) the compensation calculation method based on contaminant flux above the ultra standard is revised and (3) a compensation criterion model based on the treatment costs of sewage is proposed. In the NJP case in 2009, the average eco-compensation criterion for chemical oxygen demand (COD) is 2,000 Chinese Yuan (CNY) per ton and ammonia nitrogen (NH4-N) and total phosphorus (TP) are 8,000 CNY and 80,000 CNY per ton, respectively. Five districts needed to be compensated. The payments in the revised scheme were 4.15-586 million CNY, which were 16-48 times greater than that in the draft method. The new method can provide an important template for managers when drafting river eco-compensation schemes. © 2012 Springer Science+Business Media New York. Source


Shu J.,North China Electrical Power University | Wu L.,Clarkson University | Li Z.,Illinois Institute of Technology | Shahidehpour M.,Illinois Institute of Technology | And 2 more authors.
IEEE Transactions on Power Systems | Year: 2012

This paper presents a novel methodology for the spatial power network planning problem based on the raster map in geographic information systems (GIS). Considering candidate lines and cell linkages, the proposed spatial power network planning model integrates the optimal electric line routing and the power network evaluation, with the objective of the minimum line investment cost. The network connectivity with candidate line routes and the hourly network evaluation for peak power loads are considered to ensure the feasibility of the line path and the security of power systems. The derived mixed-integer nonlinear programming (MINLP) formulation is transformed into a mixed-integer linear programming (MILP) problem by integer algebra techniques. Furthermore, in order to improve the computational efficiency, a tighter MILP formulation with the proposed enhanced line routing constraints is proposed. Numerical case studies illustrate the effectiveness of the proposed approach for the spatial power network planning problem. © 2006 IEEE. Source


Lin X.,Huazhong University of Science and Technology | Zhao F.,Huazhong University of Science and Technology | Wu G.,China Three Gorges University | Li Z.,Huazhong University of Science and Technology | Weng H.,China Yangtze Power Co.
IEEE Transactions on Power Delivery | Year: 2012

A universal wavefront positioning correction method on traveling-wave-based fault-location algorithms is proposed. According to the location accuracy analysis for the faults of which the fault positions change successively, it is noted that the real fault distance generally cannot be divided exactly by the distance corresponding to an integer sampling interval. It will lead to unavoidable truncated error when the discrete sampling points of traveling-wave-based fault-location algorithms are applied. Furthermore, it is disclosed that the fault-location error can be limited within a single sampling interval by the simple wavefront identification method in the event of low sampling rate. In view of the aforementioned two scenarios, an appropriate correction strategy in the event of the appropriate sampling rate is put forward. The fault-location accuracy can be improved greatly with the aid of the proposed correction strategy. The effectiveness of the proposed correction strategy is verified with various typical EMTDC-based simulation test results. © 2012 IEEE. Source

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