C.N. Lu

An electricity tracing method with application to power loss allocation

Abstract This paper proposes a method for tracing the current and power flows in a network. Based on circuit theory, a node based strategy from either seller or buyers point of view is used to determine the branch current components contributed by each generator or load. After the current components are unbundled, the network is decomposed into different networks and a procedure is used to compute the bus voltages in the decomposed networks. In each network, power variables are related to only one generation or load bus. Using the computed voltages and currents, the powers flowing on the transmission lines are unbundled. To demonstrate the applications of the traced results, three-node based schemes are used to allocate losses to participants in a pool model. Test results on a six-bus system are included to illustrate the effectiveness of the proposed method. Comparison of the results with previous methods are also given.

Data extraction from a geographic information system for power system applications

This paper presents a preliminary design of an automated mapping/facilities management (AM/FM) system based on an integrated geographic information system (GIS). The GIS provides an environment for building an electric facilities database which includes graphic information and facility attribute data. The database can be used for engineering analysis, accounting and map production. Facility and network data can be retrieved by searching through the graphic and nongraphic data files. The retrieved data can then be used to form input data files for power system applications. With the powerful graphic capability of the system, simulation results can be viewed from the computer screen along with the graphic displays. In this paper, the integration of the GIS database and application software is illustrated by using a three-phase load flow program. The structure of the GIS database is introduced, and the interface programs are described. It is also shown that with the aid of GIS the facility statistic reports on system facilities can be easily established.<<ETX>>

Improving base case solution for on-line ATC calculations

The base case for computing available transfer capability (ATC) may be from the real-time state estimation (SE) or a future postulated system condition. Many existing ATC calculations are using off-line planning models. A survey result shows that most transaction business will take place in the next hour. In a network with limited transmission margins, to accommodate the next-hour market, there exists a need for an accurate real-time network model that can be used in the on-line ATC calculations. Due to the data exchange activity in the interconnected network, measurements used in an on-line model estimation might occur, say, as much as 30 seconds or several minutes apart. This paper investigates the measurement time skew effects in the real-time ATC calculations. In order to reduce the time skew effect, three measurement treatment schemes including a linear extrapolation scheme, an exponential smoothing scheme and a dynamic state estimation (DSE) are proposed. Test results show that with proper measurement updates, SE can provide a more accurate real-time base case for security analysis and ATC calculations. Costly overdesign of communication system for interarea data exchange could be avoided by using the proposed methods.

Integration of automatic mapping/facility management in distribution system analysis

Abstract This paper presents the use of an Automatic Mapping/Facility Management (AM/FM) system for distribution system analysis and design. The AM/FM provides an environment for building a database which contains both graphic information and non-graphic facility data. This database can be used by various departments for engineering analysis, accounting, inventory, map production, and so forth. This system can be used to retrieve facility data from the database and support different applications such as system analysis or planning. With the state-of-the-art graphic user interface (GUI), output results of the application can be shown on the screen along with the graphic displays of the system that includes the geographic information. In this paper, the integration of the AM/FM is illustrated by a three-phase load flow program, that is, a very precise and sophisticated three-phase distribution system model was used. It is also shown that a statistical report of facilities can be easily built with the aid of the AM/FM.

Wide area network performance study of a distribution management system

Moving towards a more competitive environment, distribution automation is considered a necessity for future power system operations. To include new automatic functions in a distribution management systems (DMS), loadings of the data links in the SCADA system will become very heavy. System upgrade or migration will need to be considered such that it can maintain a proper performance. To avoid overpaying for network equipment or services, two wide area network (WAN) architectures for a Taiwan Power Companys regional DMS are investigated. The WAN modeling is aimed to verify whether the hardware design could accommodate the communications load and ensure that transit times are within the systems functional requirements. Simulation results indicate that a WAN with distributed processing capability would provide better SCADA performance than an extension of the old centralized system that covers the feeder automations.

Vector implementations of fast decoupled and Gauss-Seidel load flows

Abstract Several vector implementations of fast decoupled load flow and Gauss-Seidel load flow are presented in this paper. Vectorized direct (W-.matrix) and iterative (preconditioned conjugate gradient) methods are used to solve the linear equations offast decoupled loadflow. A vectorization scheme for the Gauss-Seidel load flow method has also been developed. Comparisons of these methods using Alliant FX/80 and Convex 3840 computers are reported.

Communication network performance study of a high-tech park power quality monitoring system

Facing with increasingly sophisticated customers and more stringent demands on the quality of power that they supply, several utilities have installed power quality (PQ) monitoring systems to monitor the quality of the power they deliver to customers. For a PQ monitoring system that covers a great area, one of the main concerned in the design of the communication network for the system is the effect of conflicts and contention between devices on total system operation. Contention causes work to be queued or blocked from execution and system performance may suffer as a result. In this paper, a discrete event simulation technique is used to study the performance of two communication schemes for a high-tech park PQ monitoring system, one with dedicated phone lines and the other one with the corporate intranet or over large distance via the Internet. Through simulations the interactions between all devices in the system and the cause of conflict and contention can be identified. Based on the simulation results, system designers could adopt available options to increase bandwidth utilization or transmit to different bandwidth to maintain an adequate communication performance.