Guo Zhizhong

PMU placement and data processing in WAMS that complements SCADA

Although WAMS can measure power system synchronously in the time scale of millisecond. But the large amount of data it produced determines that it cannot take the place of SCADA presently. At the same time, PMU, which is the basic equipment, cannot configure at the rule of complete observability as that was done in SCADA. The configuration aims at special applications is too unilateral to apply universally. So it is necessary to find out a common PMU placement method in practice. This paper presents a PMU placement method at the rule of observability of kernel network, which was simplified by the load zone classification. By using the PMU measurement information extending method, the systems operation states can be obtained by using less PMUs. State estimation is applied to improve the precision of the processed data. This method makes WMAS accurate data complement SCADA non-accurate data effectively, and let WAMS and SCADA complement each other in practice. So, it is valuable in Mining the ability of SCADA and reducing the scale of WAMS.

Electric power grid structural vulnerability assessment

With the rapid development of economy and the increasing interdependence between national infrastructures, power system is becoming more and more complicated. Moreover, because of the deregulation of power system and the impact of power market, the deteriorated natural environment and the potential terrorism attack, power system is facing with more challenges and becomes more vulnerable than ever. So, It is necessary to assess the vulnerability of the power system, to identify the vulnerable parts so that to provide reference to protect the critical assets, develop the response to the unpredicted incidents, promote the awareness of the operators, standardize the procedure of operations and assure the safety and stability of power systems. Vulnerability assessment is a systematic project, and different methods lead to different results. The structural vulnerability of electric power grid discussed in this paper is to ascertain the ability that the system keeps integral and operates within the constraints in occasion that series equipments failed and out of service. As a common instance, node vulnerability and plain vulnerability are defined, as well as four kinds of structural vulnerability indices are defined respectively according to the violation of system limit, system adjustment, possible loss of load and sensitivity of the power on transmission line to the line impedance

Vulnerability Assessment of Cyber Security in Power Industry

Cyber system plays an important role in supervising and controlling power system. Besides its contribution of much convenience to power industry, the cyber system brings some potential danger because of its inherent vulnerability. It is significant to assess the vulnerability of cyber system, determine its risk to power industry, find out the weak parts, set appropriate response to the probable accidents and enhance the safety of the cyber system. By analyzing the threats and vulnerability of cyber system in detail, mainly including the vulnerability of SCADA (supervisory control and data acquisition) system, EMS (energy management system) and MIS (management information systems), this paper proposes two methods, the probabilistic assessment and the integrated risk assessment, to assess the cyber security vulnerability and some ways are suggested to promote the security of cyber system in power industry

Cyber Security Vulnerability Assessment of Power Industry

Cyber system plays an important role in supervising and controlling power system. Besides its contribution of much convenience to power industry, the cyber system brings some potential danger because of its inherent vulnerability. It is significant to assess the vulnerability of cyber system, determine its risk to power industry, find out the weak parts, set appropriate strategies to avoid the probable accidents and enhance the safety of the cyber system. After analyzing the threats and vulnerability of cyber system, mainly including the vulnerability of SCADA (supervisory control and data acquisition) system, EMS (energy management system) and MIS (management information systems), this paper proposes two methods, the probabilistic assessment and the integrated risk assessment, to assess the cyber security vulnerability. And some ways are suggested to promote the security of cyber system in power industry

Analysis and Treatment of Electronic Voltage Transformers Exceeded Tolerance Problem

For speeding up of substation digitization processing, transformers do not need high efficiency signal output. In the high-voltage power system, the traditional voltage transformers have been gradually replaced by electronic voltage transformer. As electronic voltage transformer based on capacitive voltage dividers excellent performance, it has become the best substitute of the traditional voltage transformer, widely used in power system. This paper presented the basic structure and analysis the experiment data. The main reasons of exceed tolerance problem is RC oscillating circuit and detention electric charge. By choosing a suitable value resistance, the problem has been solved. According to IEC60044-7, the ECVT reaches the requirement. It can completely meet the demands of the development of modern power.

Research on time process-oriented power system static security analysis

In allusion to the fact that the traditional off-line security analysis based on the data of one time section can not adapt to the continuous state change of power system appropriately, a time process-oriented security analysis method is presented in the paper. The basic idea of time process-oriented method is explained. With the abundant measurements and load forecasting information, the characteristic vector of each time section is extracted. The load curve is partitioned into several time sub-processes by the improved K-means clustering algorithm considering the successive time series of power load. The indices extracting the maximum and minimum characteristic sections of every time sub-process are defined. Then the representativeness of the characteristic sections is verified. While ensuring the static security, the time process-oriented method can improve the transmission efficiency to some extent. The calculation and analysis of IEEE 30-bus system shows the effectiveness of the method proposed in the paper.

A new topology structure and load flow solution for radial distribution networks

In this paper an efficient power flow solution with topology analysis is studied to support distribution network reconfiguration techniques in practice use. A new topology model is proposed which defined as a tree node data structure to describe the connecting relationship among the nodes dynamically. The depth-first search strategy with node storage queue technique is also used to form the tree structure rooted from the supply node. The forward and backward sweep process is accomplished with the help of the tree traversal technique. The application of recursive equations makes the program simple and concise. Numerical results are presented to illustrate the effectiveness of the proposed method.

Reactive power moment method for optimal compensation on radial distribution systems

Based on the radial structure of distribution systems, this paper proposes the concept of the reactive power moment: the linear and quadric moment of reactive power. The model of the reactive power moment is established for optimal compensation on distribution systems accordingly. The quadric moment of reactive power is used to determine the location of the capacitors. The linear moment of reactive power is used to determine the type and size of the capacitors placed on the system. This proposed method is tested on several experimental systems and test results show that this method is fast, computationally efficient, and eminently suitable for radial distribution systems.

Overview of current power industry development in China

The power industry in China has made great progress in the new century. Through power restructuring, a well-regulated power market is established. While the installed power capacity increases rapidly, much attention is put into the adjustment of power source structure. And the power network construction is trying to keep step with the expanding of power source. Along with the gradual implementation of west to east power transmission and north-south exchange project and the construction of Three Gorges Power System, the nationwide grid interconnection comes into being. With the rapid development of power system, many new technologies are put into application

A new fast method for supplying measures to avoid the high voltage mode of electromagnetic voltage transformer

A new fast method for supplying preventive measures to avoid the failure of electromagnetic voltage transformers (EMVT) due to sustained overvoltage on switch-off is proposed. This method makes full use of the characteristics of artificial neural networks and utilizes the Kohonen network model to design a classifier which can fast supply a satisfactory solution to prevent EMVT damage due to a sustained overvoltage on switch-off. Tests on a 110 kV EMVT show that the fast method has improved protection performance.<<ETX>>