Distribution Automation System with Real-Time Analysis Tools Dariush Shirmohammadi,W.H.Edwin Liu2,Ken C.Lau2,H.Wayne Hong n the past 10 years,the elec- automatic meter reading (AMR) tric power industry's involve- These analytical tools systems and its development of ment in distribution automation Energy Information Services (DA)has been principally allow effective utilization products and services through a focused on remote monitoring of existing DA infrastructures strategic alliance with Microsoft and control of the distribution and Tele-Communications,Inc. systems and their equipment. and real-time data by (TCD)are considered as preludes SCADA has constituted the most introducing intelligence to such anticipated dramatic significant attribute.Electric util- to DA/SCADA systems changes. ities in many locations around PG&E's initial efforts in adopt- the world have installed numer- ing DA technologies were princi- ous SCADA systems for their dis- pally focused on developing and tribution substations and feeders and built the installing DA infrastructure.DA infrastructure refers to infrastructure for real-time distribution operation and all components of a system for remote monitoring and control.Real-time data is available to human operators operation of distribution systems.DA infrastructure enabling them to monitor more and more events in their includes the hardware,basic operating software,and distribution systems and to control automatic equip communication protocols of the following systems: ment remotely. Master station computer system At the same time,the added volume of real-time data Telecommunication system has also created data overloads at some distribution Remote terminal units (RTUs) control centers.Without proper decision support tools, Automatic equipment operators could only rely on their past experience in Sensory devices and transducers. making operating decisions based on a subset of the The first three of these systems constitute the princi- data they receive.As a result,large volumes of real-time pal elements of a supervisory control and data acquisi- data along with much of the infrastructure built for auto- tion(SCADA)system. matic operation of the distribution systems could remain underutilized. Real-Time Applications for DA Systems This article features PG&E's approach to utilizing the In 1992,PG&E initiated an R&D project,named RADIAS (an existing infrastructures and available data more effec- acronym for real-time applications for distribution tively by introducing intelligence to DA/SCADA systems automation systems),to develop real-time analysis tools through development of advanced analytical tools for for its distribution automation systems.These analytical operations decision support. tools would allow effective utilization of the existing DA infrastructure and real-time data by introducing intelli- Distribution Automation at PG&E gence to the DA/SCADA systems.Figure 1 encapsulates Pacific Gas and Electric Company (PG&E)eagerly the objectives of the project.It indicates that the principal embraced DA from its inception.PG&E strongly believed function of the system is to transform raw data made that DA not only could enable the company to plan and available through the DA infrastructure(e.g.,SCADA data) operate its distribution systems more reliably and effi into useful information that can then be used by the oper- ciently but also could lead to products and services that ators and engineers to make informed decisions about the would dramatically change many aspects of the electric operations and planning of distribution systems. utility business. The advanced analytical tools developed under the PG&E's recent plans for large-scale installation of project include applications for state (load)estimation, fault location,power flow analysis,short circuit analysis reconfiguration,and volt/var support evaluation for dis- Shir Consultants 2 Pacific Gas and Electric Company tribution feeders.A major challenge in developing these s Opercon Systems,Inc. applications was to accommodate their real-time operat- ISN08950156/96/5.00©1996EFE Aprl199631
ing environment.This meant that client/server architecture was the models developed needed to The major accomplishment designed for the system.It inte emulate the operation of the dis- grates the advanced power sys- tribution feeders and compo- of the project lies in tem applications that run on nents in great detail and with exploiting the integrated UNIX workstations with a Win- great accuracy and the solution environment for improved dows-based graphical user inter- algorithms needed to be robust face (GUD running on PCs. and numerically efficient. computing and processing The PC/Windows-based GUI The innovations of the project, was specifically developed with however,go beyond building extensive involvement of PG&E's advanced analytical tools.The distribution operators and engi- major accomplishments are in the exploitation of the neers.This interface uses the computer-aided-design integrated environment for computing and processing.A (CAD)technology and the California grid coordinates (CGC)to offer users geographical views of PG&E's distri- bution systems encompassing topological information, line equipment data and analysis results.Street maps have also been integrated as background to enhance the Raw SCADA dntn trom various source usability of the information. Figure 2 illustrates the overall architecture of the sys- INFORMATION tem.All components of this system along with their interactions with one another are depicted in this figure. Intormation on 'system operations ineludi ·Fault Location- The main components of the system are data sources, Potertial loading or voltage problems advanced applications,and the graphical user interface. Impact of dispersed generation The components of the system have been developed Analysis Function using different,yet standard,programming languages and reside on different hardware platforms.This is par- DECISION ticularly true for the existing data sources that had been developed over the last 10 years.Hence.it was of para- Recommendation for secure and optimum operat Switching operations to isolate fauits and restore mount importance for us to adhere to industry standard .Switchind operalions to relave overload practices and tools in designing the interfaces among Canreg control to improve voltage profile and VAB these components. Mitigate the impact-of distributed resources' Control/Recommendation Functions Data Sources The source of the real-time data is mainly PG&E's exist- Figure 1.Overall objective for the RADIAS project ing distribution SCADA systems.The system extracts this data from the real-time database of the SCADA mas- ter station computers.For PG&E,the distribution SCADA Facility Database master station is mainly a PC/Windows-based system Fault SCADA Senso called WinSCADA.Real-time data is transferred to the system applications periodically through standard DATA TCP/IP communication. Fault-related data is passed by fault sensors that State (load) Saved detect and measure fault currents.If there is a fault on a Estimation distribution feeder,all the installed fault sensors along. the fault current path will report applications,their loca- tion IDs,and the fault current magnitudes they have measured. Faull Short Power Location Distribution system models and parameters as well as historical information are acquired from a distributed INFORMATION relational database named D-EDSA database.Each one of PG&E's operating divisions keeps the information on its -Volt/VAR distribution feeders in the D-EDSA database on the divi- Reconfiguration -Control: sion's UNIX workstations.Information on system models DECISION and parameters include feeder topologies,equipment locations,and data and line section parameters.Histori- Figure 2.RADIAS architecture cal information is mainly limited to line section load types 32 IEEE Computer Applications in Power
and data.Data is downloaded and improve voltage pro- via ODBC technology to RADIAS Raw data made available file. applications on request basis. through the existing DA Each application has been The data is typically transferred designed to be invoked in one on a daily basis infrastructure is transformed or more of the following ways: Another source of data is into useful decision-support time-driven,data-driven,and from the user of the system command-driven.Each method (operators and engineers).User- information for operators of invoking applications can be specified input may include and engineers selected through a point-and- request to run an application, click interface through the request to view feeder informa- graphical user interface. tion and analysis results,and specification of parameters for running an application. Graphical User Interface Furthermore,users can use the graphical user interface Computer-aided-design(CAD)technology has brought to manually update the system model and its parameters tremendous benefits to architects and designers,but locally for a specific time period or a particular study those benefits are not yet fully realized in the electric without affecting the D-EDSA master database. power industry.A CAD file can typically be characterized as a vector description of drawings with object-oriented Advanced Applications representations of drawing entities.Different objects can Advanced applications fall into two main categories: be stored in distinct layers for viewing control.Attributed applications that define and analyze distribution sys to this file design,Windows-based CAD software can tem's current operating condition;and applications that zoom in and out,pan,and drag the drawing in any multi- provide recommendations for improving the reliability, plying factor,and can locate objects and turn display lay- security,and efficiency of the current and future operat- ers on and off.Special viewing capabilities including ing conditions.Advanced applications that are designed aerial,tile,and magnifying lens can also be implemented. to define and analyze the current operating conditions The system's graphical user interface was a cus- are: tomization of the AutoPower software (developed by Distribution state (load)estimation,which esti- Opercon)that exploits the CAD concepts to offer users a mates the current operating status of a distribution near real-time friendly interface.The interface provides feeder by using limited real-time SCADA data and the 32-bit long integer module to load the feeder files in historical load data color displays and uses the CGC information to place all Distribution power flow,which analyzes what-if equipment at their respective correct locations on the scenario studies based on real- time saved cases Distribution short circuit analysis, which calculates three-phase unbalanced fault currents Distribution fault location,which determines possible fault loca- tions based on the fault sensor sig- nals and fuzzy logic algorithm. Advanced applications that are designed to make recommendations to improve the reliability,security,and the efficiency of the current operating con- ditions are: Distribution feeder reconfigura- tion,which recommends the opti- mal open/closed status of switches to isolate faults,restore services,reduce losses,and elimi- nate feeder overload. Distribution feeder voltage and var control,which recommends opti- mal tap positions and capacitor/ Figure 3.RADIAS-Vu aerial display of portions of two PG&E feeders with reactor status to minimize losses street maps superimposed Apni1199633
display.Geographical maps generated from U.S.Bureau of Census data were A9的有Ch also integrated to the display of PG&E's feeders for referencing purposes Some of the major features of the graphical user interface are: CAD displaying system with vec- tor representation of objects Vector data display with capability to zoom,pan,scroll,and drag in any scaling factors Locating drawing objects and text Special viewing through aerial,tile and lens views Layer control for displaying feed- ers and devices Toggling tie-line maps Toggling overloaded line display and line flow display Simulating switch operations or other real-time changes in the dis- tribution system parameters or Figure 4.Three mechanisms of zooming in for RADIAS-Vu topology Integrating street maps and feed- ers Window Help Open system design for linking databases,drawings,and FOR- TRAN applications 2243 Open system design for linking Microsoft office tools. 5045 A fraction of the features are shown in Figures 3 through 5.Figure 3 depicts an aerial display of portions of two 123 9942 Line Section our心eU0名群iM1 1228 PG&E feeders in Marine County,north 236 of San Francisco,superimposed on street maps constructed from mapping files.Figure 4 shows three mechanisms et动nCe t.011120 Resetance of zooming on different parts of a feed- er.Figure 5 illustrates the capability to 3 display the RADIAS analysis results for 8836 different portions of a feeder in a user- defined format. Note that this graphical user inter- face demonstrates a practical and eco nomical way to implement a simple :CGC179393 2-4150 pay oplora off Comrmuricellons version of AM/FM/GIS and SCADA inte- Figure 5.RADIAS-Vu displaying the results of RADIAS analysis gration for distribution automation applications.It links the real-time SCADA data,distribu- guages and reside on different hardware platforms.Fig- tion network model,some electrical facility information, ure 6 depicts the major components of the system and some spatial data together.It also provides opera- along with the hardware and software platforms used tors and engineers with a geographical view of the distri- for each component.The multiplicity of the frameworks bution circuits as well as real-time and study results. as well as the need for continued ease of development. support,upgrade,and interoperability encouraged us System Integration to design and develop the entire architecture and its Different components of the system have been devel- interfaces in conformance to industry standard prac- oped using different,yet standard,programming lan tices and guidelines.The data and commands between 34 IEEE Computer Applications in Power
applications on different com- is already in place in PG&E. puters are based on standard The GUI links together Future installations of applica- TCP/IP technology.The SQL*net, tions are expected to take place ODBC,and NetDDE are used to real-time SCADA data, once the field testing is success- access databases.The software the distribution network fully completed. environment is based on Socket model,some electrical programming technology both on UNIX and Windows.For a facility information, Acknowledgment Many people from PG&E's manage communication network,we cur- and some spatial data ment at R&D and Distribution depart- rently use PG&E's existing ments as well as their staff engineers LAN/WAN backbone systems. have made major contributions in developing,testing,and integrating the The objective of the system inte- RADIAS system.The authors are high- gration has been to develop a flexible architecture so ly grateful for their valuable contributions. that each component can be enhanced in the future without any difficulty For Further Reading Future Directions A.Abur,D.Shirmohammadi,C.S.Cheng,"Estimation of Switch Sta- tuses for Radial Power Distribution Systems,"Proceedings of the The system was primarily developed for operations deci- 1995 IEEE Interational Symposium on Circuits and Systems. sion support and engineering analysis.However,as the X.F.Zhang.F.Soudi,D.Shirmohammadi.C.S.Cheng,"A Distribu- components of this system have started to become avail- tion Short Circuit Analysis Approach Using a Hybrid Compensation Method"(95 WM 221-2 PWRS),IEEE Transactions on Power .Systems, able,they are considered for other applications within Volume 10,Number 4,November 1995. PG&E.Some of these planned and actual applications C.S.Cheng and D.Shirmohammadi,"A Three-Phase Power Flow are: Method for Real-Time Distribution System Analysis"(94 SM 603-1 Use of the graphical user interface as a preliminary PWRS),IEEE Transactions on Power Systems,Volume 10,Number 2, May1995. computer mapping system for marketing studies H.W.Hong,C.F.Imparato,"Integrated Support Systems for Elec- specially in identifying critical and elastic cus- tric Utility Operations,"IEEE Computer Applications in Power,Janu- tomers ay1992, Use of the applications and their graphical presen- tations to detect and identify data errors in the Biographies existing facility databases Dariush Shirmohammadi is the principal consultant and founder Use of the RADIAS applications to study power of Shir Consultants,a power engineering consulting firm in San quality problems specially as related to voltage Ramon,California.He worked for PG&E between 1985 and 1995 where his last position was director of the Energy Systems sags due to faults in adjacent feeders. Automation Group.At this position,he was responsible for devel- While a small number of analytical tools are still oping and implementing distribution automation technologies.He under development and testing,the application of the also worked in Ontario Hydro (1982-85)and Hydro Quebec (1977- 79).Shirmohammadi received his PhD in electric power engineer- system for operation decision support and planning ing from the University of Toronto in 1982.He is a senior member analysis is quite promising.System integration among of the IEEE. the SCADA,analytical applications,and graphical user Edwin Liu is a senior automation engineer at PG&E and is interface has been completed.One field test installation responsible for several advanced projects in both analytical methodology and computer application development areas.He received his PhD in 1987 from the University of California at Berke- .DATA SOURCE ley in electrical engineering and computer sciences.Before joining SCADA Maste PG&E in 1991,he worked for Empros Systems International.He Hardware:PC-Windows also taught graduate courses in San Francisco State University.He Software:C++,Delphi, is a senior member of the lEEE Visual C++ Ken Lau is a senior research associate at PG&E's Research Development department and is responsible for PG&E's R&D pro- Facility Database: gram in distribution automation.He joined PG&E in 1977 and has Hardware:SUN-UNIX Software:Oracle Database served in varlous electric distribution engineering,planning,opera- GRAPHICAL USER INTERFACE tions,and administration positions.He received his BSEE from the TCPAP,NetDDE University of California at Berkeley and is registered professional SQL Net●DBc,Socket ardware:PC-Windows electrical engineer in California. Programming,LAN/WAN Sottware:Visual-C+ Wayne Hong is the principal engineer and cofounder of Oper- con Systems,Inc..Alameda,California,a software developer spe- ADVANCED cializing in power protection,control. and engineering APPLICATIONS applications.He is also a consultant on the UCA/DAIS project.He developed the AutoPower and Fault Locating System for utilities Hardware:SUN-UNIX He worked for PG&E from 1978 to 1993.As director in the Energy Software:FORTRAN Control Center,he spearheaded the development of various engi- neering algorithms,computer applications,and system integration Figure 6.Component integration projects. Apml199635
