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New criterion for transformer differential protection to rapidly identify transferring faults

Dianli Xitong Zidonghua/Automation of Electric power systems 2007年第20期31卷 61-64+107页

作者： Yang, Qing Zheng, Tao Xiao, Shiwu Huang, Shaofeng Liu, Wanshun Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

Current transformer saturation has always been one of the major problems of degraded reliability of the transformer differential protection. The ratio restraining differential characteristic can enable the transformer protection to be immune to the mal-operation in the external fault to some extent. But how to unblock the differential protection rapidly for the transferring fault form an external one to an internal one has become a new problem. This paper presents a new method of unblocking the differential protection for the transferring fault. In the method proposed, current comparison is made between he maximal value of the integrated negative phase sequence component of the current on the two sides of a transformer and the integrated negative phase sequence component of the differential current. Based on the current comparison results, the method proposed can not only accurately identify the internal fault and the external one, but also the transferring fault developed from the external fault to the internal one. Simulation results of ATP validate the effectiveness of the method proposed.

关键词： Transformer protection

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Study on wide area measurement system based control strategy to prevent cascading trips

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第19期27卷 32-38页

作者： Xu, Hui-Ming Bi, Tian-Shu Huang, Shao-Feng Yang, Qi-Xun Ma, Rui Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

Cascading trips caused by flow transferring are the crucial reason of a lot of well-known blackouts. It threatens the security and reliability of power systems severely. A wide area measurement system (WAMS) based control strategy to prevent cascading trips caused by flow transferring is presented. By analysis of the relationship of node injection current and branch current of network, the principle of control nodes selection of load shedding and generator tripping and the calculation method of control quantity are proposed. The corresponding of the control strategy is also given. The calculation method of branch current before the control action during power system dynamic process is given. The simulation results of 10-generator 39-bus New England system show that the control strategy can prevent cascading trips effectively.

关键词： Electric power systems

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Synthetic evaluation of power quality based on extenics

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Dianli Zidonghua Shebei / Electric power Automation Equipment 2007年第12期27卷 44-47+52页

作者： Ding, Li Jia, Xiu-Fang Zhao, Cheng-Yong Li, Geng-Yin Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Baoding 071003 China

A power quality evaluation method combining extenics and AHP(Analytic Hierarchy Process) is presented. Three matter-element models are set based on power quality analysis using matter -element theory of extenics, and quantified to form relationship matrix using relation-function theory of extenics. The target weights are figured out using AHP. The final quantitative grade of the power quality is calculated based on relation-matrix and target weights. The power quality level of synthetic evaluation is obtained by combining the relationship matrix and the target weights. As an example, the power quality of PCC(the Point of Common Coupling) is evaluated, which shows that, the proposed method can evaluate power quality quantitatively and qualitatively and distinguishes different power quality levels effectively.

关键词： power quality

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Measurement-based load modeling validation by artificial three-phase short circuit tests in North East power Grid

Measurement-based load modeling validation by artificial thr...

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2007 IEEE power Engineering Society General Meeting, PES

作者： Han, Dong He, Renmu Xu, Yanhui Ma, Jin Huang, Mei IEEE Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University 102206 Beijing China Northern Jiaotong University Beijing China

ISBN: (纸本)1424412986

The researches on measurement-based load modeling have been continued for more than twenty years in China. However, since lacking of system measured data of major disturbance, it is doubtful for load model generalization capability, and more attentions are also caused for the issue that whether dynamic simulations adopting the measurement-based load model accord with the real system. The measurement-based load modeling technology was put into practice in North East power Grid in 2002, and load models based on field measurement were relatively constructed. There were four artificial three-phase short circuit tests in 2004 and 2005 respectively in North East power Grid, and the measured dynamic data from PMU and load data from load characteristics recorders validated the constructed load models and checked the generalization capability of the load model. The well generalization capability of the measurement-based load models verifies the validation of measurement-based load modeling technology. © 2007 IEEE.

关键词： Electric load management

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Cause analysis of turbine power disturbance inducing power system low frequency oscillation of resonance mechanism

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第17期27卷 83-87页

作者： Xu, Yan-Hui He, Ren-Mu Han, Zhi-Yong Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

Resonance mechanism is one of the theories that interpret power system low frequency oscillation. According to the resonance mechanism, power disturbance of prime mover can arouse power system forced low frequency oscillations. Therefore, the causes of turbine power disturbance were analyzed. The coupling model between thermodynamic system of plant and power system was set up by MATLAB. The possibility of combustion ratio of boiler and control valve of governing system disturbance inducing the variation of turbine power was researched in detail. The simulation results indicate that power system low frequency oscillations of resonance mechanism might be caused by the disturbance of control valve, when it's frequency is consistent with or close to power system natural oscillations frequency. Because of the biggish inertia of boiler, the disturbance of combustion ratio cannot invoke power system low frequency oscillation of resonance mechanism.

关键词： Electric power systems

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Flow transferring identification algorithm for multi-branches removal event with consideration of transient phenomena

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第16期27卷 24-30页

作者： Xu, Hui-Ming Bi, Tian-Shu Huang, Shao-Feng Yang, Qi-Xun Key Lab. of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

Cascading trips caused by flow transferring are the crucial causation of a lot of well-known blackouts. It severely threatens the security and reliability of power systems. Flow transferring relativity factor (FTRF) is extended from single branch removal event to multi-branches removal event. According to refraction and reflection process of flow transferring, the calculation formula of FTRF for multi-branches chain removal event is deduced. Moreover, by using the relationship of node injection currents and branch currents, a method of post-fault branch current estimation and a flow transferring identification algorithm based on WAMS to distinguish flow transferring in transient period is presented. The simulation results of 10-generator 39-bus New England system show that the proposed estimation method and the identification algorithm work well.

关键词： Electric power systems

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Multi-swing stability assessment approach based on variation rate of transient energy for power systems

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第16期27卷 13-18页

作者： Song, Fang-Fang Bi, Tian-Shu Yang, Qi-Xun Key Lab. of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

The lack of quantitative stability analysis software for power system is one of the main reasons for losing good chance to implement the emergency control and even finally resulting in the large outage. Recently, the rapidly developing wide area measurement system (WAMS) gives a new way for quick on-line quantitative transient stability assessment. Starting with the single machine energy function, the relationship between the variation rate of transient unbalance energy and multi-swing stability was analyzed in detail, and the corresponding characteristic of the variation rate of transient energy was proved. Then, a new multi-swing stability assessment criterion based on WAMS was proposed. Numerical simulations were conducted on 6-machine 22-bus system of China electric power research institute to demonstrate the effectiveness of this criterion.

关键词： Electric power systems

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Three design schemes of compensation currents for D-STATCOM used for unbalanced load

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Dianli Xitong Zidonghua/Automation of Electric power systems 2007年第1期31卷 75-79页

作者： Zhu, Yongqiang Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control School of Electric and Electronic Engineering North China Electric Power University Beijing 102206 China

Three design schemes of compensation currents for D-STATCOM in delta connection used for unbalanced load compensation are introduced. They are the schemes based on compensation principle of admittance, no zero sequence component design and an optional design method of maximum minimizing phase current. Comparisons are made considering technical indexes and engineering significance among the proposed three schemes. In serious unbalanced operating conditions, the obvious difference in amplitude among the compensation currents in three phases may lead to one or two phase overloading and the compensation capability is restricted. The optional design makes the compensation currents in three phases to be equal or close to each other as possible as it can, which is helpful to ensure the D-STATCOM having high-usage and desirable compensation effect. Similar performance can be obtained to some extent with the simpler scheme of no zero sequence component design.

关键词： Electric loads

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HV power equipment running state detection based on image processing and recognition

HV power equipment running state detection based on image pr...

引用

2006 International Conference on power system Technology, powerCON2006

作者： Shutao, Zhao Baoshu, Li Xiaohui, Zhu North China Electric Power University Baoding 071003 China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding 071003 Hebei Province China North China Electric University

ISBN: (纸本)1424401119

Aimed at the necessary on the automatic detection level in unattended substation, a new method which monitoring and diagnosis the high-voltage (HV) power equipment running state based on image processing is put forward. Image processing techniques realize and strengthen the capability of the human vision. It is a non-contact measurement method, which can monitor the HV power equipment running state online. In recent years, it is widely applied in many fields and gets plentiful and substantial success. The HV power equipment running state detection process is introduced in this paper. After image preprocesses and feature extraction, the automatic target recognition algorithm based on the radial basis function neural network (RBFNN) is presented. © 2006 IEEE.

关键词： HVDC power transmission

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Simulation validation strategy based on wide area measurement

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Dianli Xitong Zidonghua/Automation of Electric power systems 2007年第18期31卷 11-15页

作者： Ma, Jin Sheng, Wenjin He, Renmu Yue, Chengyan Zhang, Jin Rhethanz, C. Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China ABB China Research Center Beijing 100016 China

Digital simulation is the guiding tool in power system operation and control. Thus, its veracity directly affects both the security and economical operation of a power system. Since the wide area measurement system (WAMS) can provide synchronous dynamic data independent of models and parameters, this paper presents a simulation validation strategy based on WAMS to decouple the system into small areas with fewer components at different voltage levels. Therefore, by taking the measured data of WAMS as dynamic equivalent signals in digital simulation, the simulation validation work can be carried out in a much specified area and the wrong component causing the error can be found. The realization method of the simulation validation strategy proposed is also presented via the PSS/E simulation tool. Detailed case studies show the effectiveness of the method.

关键词： Electric power systems

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