March 21, 2010 Panel SessionMarch 21, 2010 Panel SessionHalf a Century of Computer Methods in Power System Analysis Planning andHalf a Century of Computer Methods in Power System Analysis Planning andHalf a Century of Computer Methods in Power System Analysis, Planning and Half a Century of Computer Methods in Power System Analysis, Planning and

Operations. A tribute to the Memory of Glenn W. Stagg and Jorge DopazoOperations. A tribute to the Memory of Glenn W. Stagg and Jorge Dopazo

Glenn W. Stagg and His Glenn W. Stagg and His Contributions to Advancing theContributions to Advancing theContributions to Advancing the Contributions to Advancing the

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Savu C. Savulescu and Sudhir VirmaniSavu C. Savulescu and Sudhir Virmani

KEY CONCEPTUAL AND KEY CONCEPTUAL AND TECHNOLOGICAL BREAKTHROUGHSTECHNOLOGICAL BREAKTHROUGHS

Conceptual breakthroughsConceptual breakthroughsƒƒintroduction of iterative loadintroduction of iterative load--flow computation methodsflow computation methodsƒƒusing large digital computers to perform power system using large digital computers to perform power system simulationssimulations

di th f SCADA t ith d ddi th f SCADA t ith d dƒƒexpanding the scope of SCADA systems with advanced expanding the scope of SCADA systems with advanced applications, thus eventually leading to the SCADA/EMSapplications, thus eventually leading to the SCADA/EMS

ƒƒgeneration control and optimizationgeneration control and optimizationƒƒgeneration control and optimizationgeneration control and optimizationTechnological breakthroughsTechnological breakthroughsƒƒusing large general purpose computers in SCADA/EMSusing large general purpose computers in SCADA/EMSƒƒusing large general purpose computers in SCADA/EMSusing large general purpose computers in SCADA/EMSƒƒperforming interactive computations as opposed to performing interactive computations as opposed to batch processing (Interactive Load Flow System)batch processing (Interactive Load Flow System)p g ( y )p g ( y )

ƒƒenvisioning the SCADA/EMS environment as a corporate envisioning the SCADA/EMS environment as a corporate data repositorydata repository

DIGITAL COMPUTER APPLICATIONSDIGITAL COMPUTER APPLICATIONS

Leading the transition to digital computersLeading the transition to digital computersƒƒintroduction of iterative methods for computing introduction of iterative methods for computing p gp gloadload--flowsflows

ƒƒusing large digital computers to perform power using large digital computers to perform power system simulationssystem simulations

ƒƒexpanding the scope of SCADA systems with expanding the scope of SCADA systems with advanced applications, thus eventually leading to advanced applications, thus eventually leading to the SCADA/EMS conceptthe SCADA/EMS concept

ti t l d ti i titi t l d ti i tiƒƒgeneration control and optimizationgeneration control and optimization

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

The Essential ApplicationsThe Essential ApplicationsƒƒLoad Flow Load Flow ƒƒTransient StabilityTransient StabilityƒƒShort Circuit (Fault) AnalysisShort Circuit (Fault) Analysis( ) y( ) y

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

Foresight Foresight "Unless the user community, which relied heavily "Unless the user community, which relied heavily y yy yon these studies, fully accepted their digital on these studies, fully accepted their digital computer implementation, they would be reluctant computer implementation, they would be reluctant

h l d li i "h l d li i "to accept the more rarely used applications"to accept the more rarely used applications"

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

The Stagg and ElThe Stagg and El--Abiad BookAbiad Bookƒƒbasic philosophy and attention to detail basic philosophy and attention to detail illustrated illustrated p p yp p yby this bookby this book

ƒƒtopics are addressed clearly, completely and with topics are addressed clearly, completely and with many worked out examplesmany worked out examples

ƒƒstandard reference for many yearsstandard reference for many years

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

The Gauss & Gauss Seidel Load FlowThe Gauss & Gauss Seidel Load Flowƒƒincludes formulation of the Zincludes formulation of the Z--bus, Zbus, Z--loop and Yloop and Y--bus bus ppmatrices (matrices (material usually found in books on circuit material usually found in books on circuit theory)theory)

ƒƒGauss Iterative Methods using Gauss Iterative Methods using YY--bus are bus are described described clearly and conciselyclearly and concisely

ƒƒit remains a useful tool today in special it remains a useful tool today in special applicationsapplications

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

Fault Fault AnalysisAnalysisƒƒthree phase networks are analyzedthree phase networks are analyzedp yp yƒƒ++-- 0 sequence transformation and the0 sequence transformation and theƒƒClarke’s alpha, beta, zero Clarke’s alpha, beta, zero components are components are describeddescribedp , ,p , , ppƒƒYY--bus bus and and ZZ--bus bus formulations are covered formulations are covered

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

Fault analysis Fault analysis -- the the ZZ--bus bus ƒƒYY--bus bus formulation required a complete iterative formulation required a complete iterative q pq psolution for each fault type and not used generallysolution for each fault type and not used generally

ƒƒUse of Use of ZZ--bus bus made it feasible to use Thevenin's made it feasible to use Thevenin's Theorem for short circuit calculations Theorem for short circuit calculations

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

Numerical integration Numerical integration ƒƒChapters 9 and 10 provide a clear explanation of the:Chapters 9 and 10 provide a clear explanation of the:p p pp p p

Euler and modified EulerEuler and modified EulerPicardPicardRungeRunge--Kutta and Kutta and Milne's predictor corrector methodsMilne's predictor corrector methods

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

The synchronous machine models The synchronous machine models ƒƒdescriptions include:descriptions include:

derivation of swing equation, derivation of swing equation, the dthe d--q axis phasor diagram q axis phasor diagram electrical equations (except for damper electrical equations (except for damper windings)windings)

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

Glenn Stagg Glenn Stagg -- the practical visionarythe practical visionaryƒƒa 2000 bus transient stability program was a 2000 bus transient stability program was developed in developed in 19671967--1970 1970 with:with:

detailed synchronous and induction machine models detailed synchronous and induction machine models the ability to synthesize arbitrary excitation system modelsthe ability to synthesize arbitrary excitation system modelsuse the fourth order Rungeuse the fourth order Runge--Kutta methodKutta method

performance guidelines (LF and TS)performance guidelines (LF and TS)ƒƒperformance guidelines (LF and TS) performance guidelines (LF and TS) to run efficiently on IBM 360 mainframes to run efficiently on IBM 360 mainframes

ƒƒuse Assemblyuse Assembly language tolanguage toƒƒuse Assembly use Assembly language tolanguage tominimize processing minimize processing overheadsoverheadsmeet performance requirements and memory meet performance requirements and memory constraints constraints p q yp q y

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

The BreakthroughThe Breakthroughƒƒacceptance of LF and TS digital simulations was a acceptance of LF and TS digital simulations was a major step in converting the AEP engineers to the major step in converting the AEP engineers to the use of digital computers use of digital computers

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

Soon other Digital Computer Applications Soon other Digital Computer Applications gained acceptance at AEPgained acceptance at AEPƒƒBPA's EMTPBPA's EMTPƒƒEconomic DispatchEconomic DispatchƒƒHydro SchedulingHydro SchedulingƒƒState Estimation, etc.State Estimation, etc.ƒƒaccounting, payroll and other financial and business accounting, payroll and other financial and business

DIGITAL COMPUTER APPLICATIONS DIGITAL COMPUTER APPLICATIONS (cont'd)(cont'd)

Glenn Stagg Glenn Stagg -- the entrepreneurthe entrepreneurƒƒin 1970 to formed Stagg Systems, Inc. with three in 1970 to formed Stagg Systems, Inc. with three others others

ƒƒStagg Systems was the first to implement large Stagg Systems was the first to implement large Energy Management Systems in general purpose Energy Management Systems in general purpose (IBM 370) computers(IBM 370) computershihi t ib ti tt ib ti t EMS SCADAEMS SCADA d ib d td ib d tƒƒhis his contributions to contributions to EMS SCADA are EMS SCADA are described nextdescribed next

ENERGY MANAGEMENT SYSTEMSENERGY MANAGEMENT SYSTEMS

The early days of online computing in system The early days of online computing in system operationsoperationsƒƒuntil mid 1950s, telemetering and control were until mid 1950s, telemetering and control were predicated on analog technologypredicated on analog technology

ƒƒAEP, where Glenn Stagg became Assistant Vice AEP, where Glenn Stagg became Assistant Vice president for Computer Applications in 1958, president for Computer Applications in 1958, started to use onstarted to use on--line digital computers in power line digital computers in power system operations in the early 1960ssystem operations in the early 1960s

economic dispatcheconomic dispatcheconomic dispatcheconomic dispatchrealreal--time system monitoringtime system monitoringindustry first successful state estimatorindustry first successful state estimatorindustry first successful state estimatorindustry first successful state estimator

Dopazo, J. F., Stagg, G. W., Klitin, O. A. and Vanslyck, L. S., "State Calculation of Dopazo, J. F., Stagg, G. W., Klitin, O. A. and Vanslyck, L. S., "State Calculation of Power Systems from Line Flow Measurements", IEEE Transactions on PAS, VOL. Power Systems from Line Flow Measurements", IEEE Transactions on PAS, VOL. PASPAS--89, No. 7, September/October 1970, pp. 169889, No. 7, September/October 1970, pp. 1698--17081708

ENERGY MANAGEMENT SYSTEMS ENERGY MANAGEMENT SYSTEMS (cont'd)(cont'd)

The insight: using large scale The insight: using large scale general purposegeneral purposecomputers to implement the complete functionality of a computers to implement the complete functionality of a SCADA/EMSSCADA/EMSSCADA/EMSSCADA/EMS

ƒƒSCADA/EMS industry in the early 1970s (and throughout SCADA/EMS industry in the early 1970s (and throughout many subsequent years):many subsequent years):many subsequent years):many subsequent years):

most systems based on somost systems based on so--called "process computers" (mini and supercalled "process computers" (mini and super--minicomputers)minicomputers)

Stagg Systems in the early 1970s:Stagg Systems in the early 1970s:ƒƒStagg Systems in the early 1970s:Stagg Systems in the early 1970s:general purpose IBM 370 family architecture at the core of the general purpose IBM 370 family architecture at the core of the SCADA/EMSSCADA/EMS

––first large scale, full function SCADA/EMS implemented by Stagg first large scale, full function SCADA/EMS implemented by Stagg Systems at Southern Company ServicesSystems at Southern Company Services

––first implementation of the "weighted least squares" state estimatorfirst implementation of the "weighted least squares" state estimatorƒƒ... fast forward 20 ... fast forward 20 -- 30 years later:30 years later:

onlyonly general purpose machines... general purpose machines...

ENERGY MANAGEMENT SYSTEMS ENERGY MANAGEMENT SYSTEMS (cont'd)(cont'd)

Deploying advanced applications that can be Deploying advanced applications that can be used both offline and in realused both offline and in real--timetimeƒƒInteractive Load Flow (ILF) SystemInteractive Load Flow (ILF) System

extended the batch algorithm with interactive capabilitiesextended the batch algorithm with interactive capabilitiescould be installed and would operate efficiently on acould be installed and would operate efficiently on a

––corporate computer facility utilized for online and batch processing corporate computer facility utilized for online and batch processing of commercial as well as engineering applicationsof commercial as well as engineering applicationsof commercial as well as engineering applicationsof commercial as well as engineering applications

Detroit Edison Company Detroit Edison Company ---- IBM System/370 Model 158 corporate computer IBM System/370 Model 158 corporate computer facilities also used for Customer Information System (CIS) and batch facilities also used for Customer Information System (CIS) and batch processing of accounting and engineering workprocessing of accounting and engineering work

––realreal--time computer system for power system control and security time computer system for power system control and security assessmentassessment

Southern Company Services SCADA/EMSSouthern Company Services SCADA/EMSpresented during the firstpresented during the first--ever IEEE session dedicated to ever IEEE session dedicated to interactive computing (PICA 1975)interactive computing (PICA 1975)

ENERGY MANAGEMENT SYSTEMS ENERGY MANAGEMENT SYSTEMS (cont'd)(cont'd)

Anticipating the futureAnticipating the futureƒƒThe control center as an information resourceThe control center as an information resource

became a major theme in speeches and presentations conducted became a major theme in speeches and presentations conducted by Glenn Stagg in mid 1980sby Glenn Stagg in mid 1980sformed the foundation of SCADA/EMS solutions delivered byformed the foundation of SCADA/EMS solutions delivered byformed the foundation of SCADA/EMS solutions delivered by formed the foundation of SCADA/EMS solutions delivered by Stagg SystemsStagg Systems

ƒƒAvoiding recurring obsolescence Avoiding recurring obsolescence ---- Glenn Stagg:Glenn Stagg:argued that using offargued that using off--thethe--shelf computers and software that shelf computers and software that belong to an upward compatible product line was key to assuring belong to an upward compatible product line was key to assuring the permanence of the SCADA/EMS solutionthe permanence of the SCADA/EMS solutionthe permanence of the SCADA/EMS solutionthe permanence of the SCADA/EMS solutionanticipated the era of de facto standards for portability and anticipated the era of de facto standards for portability and interoperabilityinteroperability

"as new systems technology advancements develop utility computer systems must have the"as new systems technology advancements develop utility computer systems must have theas new systems technology advancements develop, utility computer systems must have the as new systems technology advancements develop, utility computer systems must have the builtbuilt--in flexibility to incorporate them without extensive, meaning prohibitively expensive, in flexibility to incorporate them without extensive, meaning prohibitively expensive, retrofitting"retrofitting" -- Stagg, G. W., '''Energy Management Systems: How to Cope with the Future," 118 Stagg, G. W., '''Energy Management Systems: How to Cope with the Future," 118 Public Utilities Fortnightly 52, July 24, 1986Public Utilities Fortnightly 52, July 24, 1986

CONCLUSIONSCONCLUSIONS

Highlighted a few of Glenn's contributions to the Highlighted a few of Glenn's contributions to the development and acceptance of digital development and acceptance of digital computers in the electric utility industrycomputers in the electric utility industryIncluded some of his key insights that were Included some of his key insights that were y gy gahead of their timeahead of their timePersonal and professionalPersonal and professional tributetribute of the panelof the panelPersonal and professional Personal and professional tribute tribute of the panel of the panel members to a giant of the industry who shaped members to a giant of the industry who shaped our careers and set an example thatour careers and set an example that allall of usof usour careers and set an example that our careers and set an example that all all of us of us continue to followcontinue to follow