Developing a voltage-stability-constrained security assessment system part I: Determination of power system voltage security operation limits

The method for determining the voltage security operation limits in a practical voltage security analysis (VSA) system based on VSAT software for large power systems is introduced in this paper. These operation limits include bus voltage limits, branch/corridor transfer power limits and P-load limit of the whole system. The voltage security operation limits are determined by the most critical contingency among the studied contingency set. The most critical contingency determines the P-load limit of the whole system, and all kinds of operation parameter limits are operation parameter values corresponding to this P-load limit under pre-contingency. An operation parameter limit is upper limit if the function relationship between this operation parameter and load power is an increasing curve, or lower limit if the function relationship between this operation parameter and load power is an decreasing curve. These operation parameter limits are helpful for operators to monitor the system operation state. © 2005 IEEE.published_or_final_versio

Developing a voltage-stability-constrained security assessment system part II : Structure and function design and technology used

This is the second part in a two-part paper on the development of a voltage stability constrained security assessment system (VSC-SAS). In this part, overall VSC-SAS structure and function design and technology used will be presented. The system is expected to be used in both on-line and off-line modes. In on-line mode, on-line SCADA/EMS data will be used for VSC-SAS use; while in off-line mode (usually day-ahead calculation), historical data can be used for VSC-SAS. Both results (i.e. system operation limits) can be selected to compare with real time operation conditions and supervision power system operation security margin. © 2005 IEEE.published_or_final_versio

How Ethnic Minority Students Perceive Patterns in Chinese Characters: Knowledge of Character Components and Structures

This chapter assesses ethnic minority (EM) adolescent Chinese as a Second Language (CSL) learners’ perception of visual patterns in Chinese characters and examines the role of component and structural knowledge in CSL beginner and intermediate level curricula. In this exploratory mixed methods study, 213 Grades 7 to 11 EM students of different ethnic origins in Hong Kong and Macau without prior training in components and spatial configurations of Chinese characters completed a set of tests that measured their character component and structural knowledge, including (i) the Separation of Character Components Test; (ii) the Constitution of Character Components Test; and (iii) the Character Structure Test. Five ways of componential analysis of Chinese characters, namely (1) unanalytical agglomeration of strokes; (2) agglomeration of sequenced strokes; (3) arbitrary repetition of (parts of) component; (4) hybrid agglomeration of strokes and components; and (5) agglomeration of components, were identified to be used by the participants. The participants’ television viewing habits had a significant effect on their performance on the test; however, overall, their demographic background and after-school activities had no significant effects on their test performance. With reference to the findings, recommendations on enhancing EM adolescent CSL learners’ orthographic awareness for literacy success are given towards the end of the chapter. In particular, an Integrative Perceptual Approach for Teaching Chinese Characters (Tse, Marton, Ki, & Loh, 2007) is recommended for teaching orthographic knowledge in a way that is beneficial to students’ all-round second language (L2) development

Developing a Power System Dynamic Security Assessment System, Part II: structure and function design and technology used

This is the second part in a two-part paper on the development of a power system dynamic security assessment system (DSA). In this part, the overall structure, function design and technology used of a DSA tool including TSA- transient stability assessment, VSA- voltage stability assessment is presented. The system is expected to be used in both on-line and off-line modes. In on-line mode, real-time SCADA/EMS data will be used with specific time interval; while in off-line mode (usually day-ahead calculation), historical data can be used for DSA. Both results involving TSA and VSA can be integrated and selected to compare with real time operation conditions and supervision power system operation security margin.link_to_subscribed_fulltex

Implementation of a power system dynamic security assessment and early warning system

A real time dynamic security assessment and early warning (DSAEW) system for the purpose of keeping interconnected power systems operating in security region, monitoring dynamic security margin constantly and ensuring system operation reliability is proposed in this paper. The framework of the DSAEW system is designed in accordance with Client/Server and Browser/Server models based on the TCP/IP protocol. In this paper, the overall system architecture, function design and technology used of such tool including TSA- Transient Stability Assessment, VSA- Voltage Stability Assessment is presented. Furthermore, the calculation of some operation limits involving the bus voltage limits, the branch/corridor transfer power limits and the P-load limit of the whole system is introduced in this paper as well. On one hand, the DSAEW system can easily and conveniently integrate with existing Energy Management System (EMS) to implement the real time dynamic security assessment. On the other hand, the DSAEW system can make intensive dynamic analysis related to the specified case study as an off-line simulation platform. © 2007 IEEE.link_to_subscribed_fulltex