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Zhang J.,State Grid Corporation of China | Su X.,State Grid Corporation of China | Xia Y.,Join Bright Digital Power Technology Co.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2015

750 kV grid as the main grid of Northwest China is now in rapid development period. On the basis of the characteristics of 750 kV transformer, the protection configuration and its related problems are analyzed. Considering that the differential protection of 750 kV transformer is quite perfect, the internal fault is mainly dependent on the differential protection to remove and the backup protection is primarily responsible for external faults at the bus and the local end of the adjacent lines. To meet the requirements for sensitivity and speed at external local faults without losing selectivity is the key issue for setting calculation in transformer backup protection. Based on the above analysis, the setting calculation method for 750 kV transformer protection is proposed and the applicability of impedance protection, improvement of differential protection, simplification of backup protection and automatic setting calculation of transformer protection are discussed as well. The scheme has been successfully applied to the 750 kV transformer protection in Northwest China. ©, 2015, Power System Protection and Control Press. All right reserved.

Mu Z.,North China Electrical Power University | Xu Y.,North China Electrical Power University | Qiu X.,Join Bright Digital Power Technology Co. | Zhang T.,Shijiazhuang Electrical Power Company
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2014

It is proposed to sequentially assess the protection settings according to the importance of branches for improving the efficiency of its online setting assessment. As the branches vulnerable to power flow impact may easily cause fault and induces cascading faults after trip-off, the power flow entropy is thus applied to assess the importance of branch. The possibility of cascading faults induced by the trip-off of faulty branch is assessed by the index Q1i based on the power flow transfer entropy and the vulnerability of branch to power flow impact is assessed by the index Q2i based on the power flow distribution entropy. The product of Q1i and Q2i is thus applied to assess the importance of branch. The simulation for IEEE 3-generator 9-bus system verifies the correctness of the proposed method. The distribution factor method is recommended to simplify the calculation of branch power flow variation.

Yang X.,North China Electrical Power University | Wang J.,Join Bright Digital Power Technology Co. | Hou M.,Baoding Well Foundry Machinery Co. | Fan X.,North China Electrical Power University
Proceedings of 2015 IEEE Advanced Information Technology, Electronic and Automation Control Conference, IAEAC 2015 | Year: 2015

This paper briefly introduces the principle and characteristics of genetic algorithm, as well as the basic operation and the solving steps. The fitness function was built based on the objective function. The operator algorithms of replication, crossover and mutation were designed. The flexible job shop scheduling is optimized by designing the program based on MATLAB using the genetic algorithm. The genetic algorithm in this paper is tested on instances taken from the literature and compared with their results. The computation results show that the genetic algorithm referred in this paper is feasible and effective. © 2015 IEEE.

Zhao H.,North China Electrical Power University | Huang J.,North China Electrical Power University | Niu Y.,Beijing Electric Power Company | Li L.,Join Bright Digital Power Technology Co. | Zhou Q.,Join Bright Digital Power Technology Co.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2012

A scheme is put forward to solve the problems occurred in the radial network operation mode combination of the integrated setting calculation system, which directly sets the power supply paths to automatically form the power supply operation mode. The power supply mode is composed of the substation mode and line mode. System searches for the power points automatically and the power paths under each power point are set manually. The power supply operation mode is then automatically generated by system. Practical application shows that the scheme solves the complicated operation mode combination of integrated setting calculation system and the exceptional operation conditions of radial network, such as multiple sources and large power supply transfer, which improves the calculation speed and increases the system practicability and universality.

Yan L.-J.,North China Electrical Power University | Yang S.-Y.,North China Electrical Power University | Ni L.-Q.,East China Grid Company | Gong R.-M.,Join Bright Digital Power Technology Co. | Zhou Q.-J.,Join Bright Digital Power Technology Co.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

Based on the structural differences between autotransformer and normal transformer, methods of computing zero sequence circuit parameters and common branch zero sequence circuit of autotransformer with neutral point grounding by small reactance are introduced with proposing the notable problems. Constitution characteristics of 500 kV autotransformer protection are analyzed, and the backup protection configuration and setting process are simplified according to the principles of "strengthen main protection, simplify backup protection", which not only simplifies the multi-step configuration of back protection, but also cancels zero sequence current protection of high and medium voltage side, meanwhile the theoretical basis and process are expounded. Making a fault analysis, setting calculation and the protection action simulating on an instance by the software of the protection setting and simulation, the result demonstrates that this back-up protection has a reliable action, simple logic, and can be easily realized.

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