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Wang S.,Guangdong Electric Power Design Institute
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2011

According to the characteristics of micro-grid and distributed generation, the design, operation, optimization and control of micro-grid are discussed. With an engineering example, its design principle is pointed out: reliability, flexibility and power balance. Its configuration and operational modes are analyzed. The parallel mode, island mode and dual mode are described and their design characteristics are presented. Suggestions are made for the control system and optimized operation of micro-grid and distributed generation, and the overall concept of MEMS(Micro-grid Energy Management System) is proposed. Some issues, such as anti-island protection and short-circuit current, are explained. The solution of anti-island protection applying active and passive detections is submitted. Source

Xie C.,Guangdong Electric Power Design Institute
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2014

In a nuclear power plant, between the generator terminal and the step-up transformer, generator circuit breakers are installed, and generator circuit breaker failure protection is also installed. This paper analyzes the protections and the value settings of the nuclear power plant generator, and points out the problems in the generator circuit breaker failure protection design. First, in the protection of some jump starter generator circuit breakers, de-excitation, and the main valve closing, as the current criteria are not satisfied, the starter generator circuit breaker failure protection cannot be directly activated. Secondly, during the turbo-generator program tripping process, the generator circuit breakers break down and cannot trip, neither can the generator circuit breaker failure protection be activated. Based on the harm caused by these problems, this paper proposes some improvements on the nuclear power plant generator breaker failure protection design, further improving the generator circuit breaker failure protection design in the nuclear power plant. © 2014 State Grid Electric Power Research Institute Press. Source

Wang C.-C.,Guangdong Electric Power Design Institute
Dianwang Jishu/Power System Technology | Year: 2010

In ±500 kV DC power transmission project from right bank hydropower station in Xiluodu to Guangdong province, following technologies, such as the transmission line structure of double DC circuit on the same tower, common starting point and ending point for both DC lines, common converter station and sharing equipments in UHVAC yard, are adopted. The hierarchical structure of DC control system for this project, the configuration and jurisdiction of control functions, the coordinative control between two DC transmission circuits and the configuration of backup reactive power control function are discussed, and three kinds of feasible hierarchical structural schemes are proposed and related technical comparison among these schemes are performed. According to comparison results the scheme, a DC control system, which consists of an independent DC controlling hierarchy for double circuit lines, i.e., the control in station hierarchy, a bi-pole control hierarchy and pole control and converter control hierarchy, is recommended as optimal scheme. Source

Peng M.-X.,Guangdong Electric Power Design Institute
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

Based on the limit equilibrium theory, the backfill is treated as a perfectly elastic-plastic material which follows the Mohr-Coulomb yield criterion, and is assumed to be an isotropic, homogeneous and incompressible (or non-expansive) perfectly continuous medium. The stress singularity and its stress boundary condition are introduced, and a statically determinate and solvable mathematical model for the limit equilibrium boundary value problem is established without considering the stress-strain relationship. Then the slip-line field and stress field in plastic zone of the backfill are solved by use of the slip-line method, furthermore, the passive earth pressure on retaining walls and the reaction on slip surfaces are derived. Geometric and mechanical similarity principle is presented by means of dimensionless analysis. The results show that the slip-line solution to the passive earth pressure is generally less than or equal to the Coulomb's solution, and the classical Rankine's earth pressure or the classical Coulomb's earth pressure satisfying non-singularity condition is in accordance with the slip-line solution, and the Hencky's first theorem and second theorem are not generally applicable. Source

Peng M.-X.,Guangdong Electric Power Design Institute
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

The problem of critical depth for plastic zone behind the retaining wall has not yet been solved well. The conventional calculation formula is only applicable for some special cases. This paper is based on the limit equilibrium theory, in which the backfill is treated as a perfectly elastoplastic material following the Mohr-Coulomb yield criterion; and it is assumed that a family of slip lines in the plastic zone are straight lines, i.e. the plane slip surfaces. The elastic overburden is put forward to replace the conventional tension crack; and a more reasonable slip wedge analysis model is established. The analytical solutions of the plastic critical pressure and critical depth and the possible maximum depth in plastic zone for active earth pressure on retaining wall in general case are deduced using limit equilibrium method. The calculation results show that the analytical solution of the plastic critical depth is identical with the result by iterative calculation in existing literatures and the conventional calculation formula is a special case of this analytical solution. Source

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