Dahai You

Review on blackout process in China Southern area main power grid in 2008 snow disaster

In the beginning of 2008, southern China had experienced extreme low temperature, heavy rain, snow, and freezing weather. This extreme weather had impaired the southern area power grid greatly and threatened the security and stability running of power system and power supply. The paper introduces the China southern area power grid basic disaster situation. Based on the China southern area power grid characters and the disastrous weather characters, it reviews the whole accident process of the 500kV main power grid in the snow disaster. Then summarizes the typical characteristics in the disaster of China southern area 500kV main power grid, and reveals the main problems exposed in the southern area 500 kV main power grid. The problems include: long distance large capacity transmission line proportion, the power supply development is not harmonious with the power grid development, and the 500kV transmission line corridor selection problem, etc. Some solutions and recommendations in power supply development and power grid development are given out according to the problems in the end.

A novel communication network for three-level wide area protection system

Wide area protection is the system protection against the electric power system wide area disturbance based on the modern measurement and communication technology. The three-level structure is a good structure for wide area protection system (WAPS), but it relies on high-performance communication system. The purpose of this paper is to design a suitable communication network for the three-level WAPS. By analyzing the communication needs of the WAPS, the authors divide messages need to be transmitted into several sorts, and determine the demands of various messages for communication system. Based on that, the optical fiber is selected as the communication medium, and the broadband integrated service digital network based on SDH/SONET and ATM is selected as the network type. A network topology of mixed ring-star is designed. The network makes full use of the IEC 61850 based LAN in substation and power plant. Then, the protocol sets for the key message transmissions are determined. Finally, the transmissions of key messages are simulated using OPNET modeler. The simulation result satisfies the real-time and reliability demands even under the worst situation, which confirms the effectiveness of the communication system.

Development of wide area current differential protection IED based on IEC 61850

Nowadays power system structure are becoming more and more complex. Capacity exchanged are increasing day and day, and voltage level of the network are raised continually. Those brings new challenge on network security. Security and stability of network depends on correct and rapid action of relay protection devices. With developed communication network technology, current differential protection can be introduced into wide area network. Duplicated protection can be made up with it and traditional protection. On the other hand, it can be also a now backup protection scheme which has faster action speed than traditional one. Using hierarchical function structure, uniform object model and abstract communication service interface of IEC 61850 as reference, modeling of wide area current differential protection IED is given. The model insures interoperability between IEDs. Hardware of wide area current differential protection IED is designed in this paper too. Plug-in hardware module are designed to constitute IED. The mapping relationship between logical device and plug-in hardware module is also depicted.

Analysis on the influencing factors of transformer sympathetic inrush current

Closing a transformer without load will lead to the emergence of sympathetic inrush current in adjacent transformer. Sympathetic inrush current always causes mal-operation of protective relay and harmonic over-voltage. Based on simplified equivalent circuit of two shunt-wound transformers, the magnetic analytical expression and rule of bias magnet attenuation are analyzed. After that, the reasons of sympathetic inrush current generation are illustrated. The effects of initial close angle, system resistance, load of transformer, shunt-wound capacitors, residual flux linkage connection in series and manner of grounding to sympathetic inrush current are then analyzed deeply. The conclusion is validated using emulate program. The conclusion of this paper is valuable in estimating the reasons of sympathetic inrush current and eliminating it.

Analysis of vulnerabilities in China's Southern Power System using data from the 2008 snow disaster

Early in 2008, some areas in southern China (especially Guizhou, Guangxi, Yunnan and Guangzhou Provinces) experienced extreme low temperature, heavy rain, snow, and freezing weather, which seriously damaged the power system. Based on the general disaster situation, this paper describes characteristics of local power grids in each province and the processes through which they broke down. Some detailed analysis on the potential risks and problems exposed in Chinas southern power grid are discussed, focusing on the energy structures, power plant distributions, power grid structures, primary equipment, second ary equipment and emergency control mechanisms. We then sugguest some solutions to reduce the likelihood of power grid breakdown in the future, and propose ideas for future research.

Bay level IED modeling and realizing using IEC 61850

Interoperability is the most important objective of IEC 61850. Model design and realization are critical steps to implement IEC 61850 and achieve interoperability. Based on analysis of interoperability support, a universal design method of IED model is given, and problems of bay level IED model realization are analyzed. Bay level IED is embedded system, and its information models are usually realized in the form of data structures. Several existing data structures are analyzed with the view point of interoperability. And a new data structure named as ASCI-FC-data structure is designed. Unlike other data structure, it includes FCs (functional constraints), and shows the true hierarchical structure of information model at the same time, which makes it better to support interoperability. Then data store structure making use of binary chain list is given with examples to prove the advantages of it in object locating and traversing. A method of FC filtering for ASCI-FC-data structure stored in binary chain list is also given to show the advantages of this data structure.

A Method for Assessing Power System Security Risk

All along, countries of the world have adopted different methods to guarantee the operation security of power system. However, there were still a lot of large-area power outages in the world recently, which causing enormous economic losses. It indicates that the existing methods cannot completely guarantee the security of power system, and there is an urgent requirement to find new ways as a supplement. In this paper, an operable method for assessing power system security risk has proposed. Based on the analysis of the cooperation of the government and enterprises, the assessment process is discussed. The assessment indices are given by the Accident Tree Analysis and Analytic Hierarchy Process. Finally, we take Guangdong power grid as an example to briefly describe the practical application of the method.

Research on Protection Equipment with Digital Interface Based on IEC-61850

A newly developed microcomputer relay protection with digital interface is presented. It adopts digital optical communication technology and Ethernet network instead of traditional metallic cable. Therefore it can highly enhance the anti-interference ability and reliability of the protections. The hardware structure and software pattern are introduced respectively. The new protection adopts the high-speed DSP TMS320VC33 as its hardware platform and RTL8019AS as the Ethernet controller. Task scheduling is based on multi-task mechanism. Ethernet communication tasks priority is lower than the sampling task and the protection task but higher than the keyboard and display tasks. Switches among tasks are realized by dispatching and receiving signals. Some performance test results are presented in the end and prove the new protections potential to be realized in the field in future.

Research on improvements of using electronic current transformer on distance protection

Traditional magnetic current transformer (CT) always has the problem of saturation, which depresses the accuracy of distance protections impedance measurement and shortens its protection zone. Based on this analysis, traditional measures to solve this problem are summarized first, and then the newly developed electronic current transformer (ECT) is introduced as a new way to solve the problem. Because of its high accuracy, high stability, wide frequency band, and most of all, without the problem of magnetic saturation, ECT has become a popular substitute for traditional CT. It can improve the starting unit, phase selecting unit, impedance unit and other functional units of distance protection. Experimental analysis shows that using ECT instead of traditional CT can enhance the operating accuracy and reliability of distance protection greatly.

A Newly Developed Line Protection with Ethernet Communication Interface Based on 1EC61850

As more and more users require the microprocessor protection device has Ethernet interface based on IEC61850, a newly developed relay protection equipment based on DSP with Ethernet communication interface is introduced. The hardware circuit design, drive program and TCP/IP protocols are developed in detail to explain how to realize the Ethernet communication. We use DSP TMS320VC33 as the hardware platform and RTL8019AS as the Ethernet control chip. RTL8019AS is connected with DSP by (complex programmable logic device) CPLD. The integral layer model for Ethernet communication is a seven layers model based on IEC61850. The transport layer uses UDP protocol to transport data, as it is faster and more efficient. It can finish the Ethernet communication task and switch to other tasks by sending out and releasing signals to DSP. Experiment shows that it can satisfy HOkV line and below voltage relay protections technology requirement to Ethernet communication successfully.