Toward effective substation automation

may/june 2007 IEEE power & energy magazine 671540-7977/07/$25.00©2007 IEEE

BBECAUSE THE TENNESSEE VALLEY AUTHORITY’S (TVA) TRADITIONAL SUBSTATIONpractice has become an increasingly ineffective framework for meeting business expectations, TVAhas launched a bold initiative to radically transform its standard practice. The cornerstone for thisnew practice is the IEC 61850 communications standard, augmented with complementary technolo-gies and procedures. TVA believes this approach has the potential to not only streamline the substa-tion’s application environment for advanced capabilities but also save enormous resources inconstruction, operations, maintenance, and data management, whether building a new site or refur-bishing an existing one. These savings will be achieved by aligning all aspects of substation practicewith the communications network and the opportunities it offers.

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68 IEEE power & energy magazine may/june 2007

The site of this project is the new 161-kV to 500-kVBradley substation, being constructed approximately 25miles east of Chattanooga, Tennessee. in Bradley County(see Figure 1 and Figure 2). This is TVA’s biggest transmis-sion upgrade in the Chattanooga area in nearly 3 decades.Eventually, there will be a 230-kV yard as well. The facilityis expected to begin service in May 2008.

Four Key DefinitionsBefore this discussion proceeds, a few simplified definitionsare in order. They should make descriptions clearer andhopefully aid the reader. These are not universal definitionsbut should be taken in the context of this article.

✔ The primary system comprises substation equipmentthat directly carries, conditions, transforms, and inter-rupts power. Examples include buses, lines, transform-ers, load tap changers (LTCs), switches, breakers,capacitor banks, and reactors. We may also refer to thisequipment collectively as the power infrastructure.

✔ The secondary system comprises all components andsystems used to monitor, control, protect, and auto-mate the substation. Examples include PTs, CTs,transducers, control panels, protection relays, measure-ment devices, meters, transducers, controllers, RTUs,data communications equipment, and human machineinterface (HMI). We may also refer to this equipmentcollectively as the technology infrastructure. It is criti-cal to human and equipment safety, system reliability,and the execution of all other utility applications relat-ed to the substation.

✔ Integration refers to the integration of data and/orfunctionality for the benefit of applications. Withoutapplications, there would be no need for data, func-tionality, communications, or integration. Applications

rule. Integration may be performed by the applicationthat directly needs it or by another automated processthat can serve the needs of multiple applications (e.g.,a proxy server or repository). The specific approachesadopted by a utility are a local assessment and imple-mentation issue.

✔ Automation typically refers to substation applicationsthat produce information, control actions, or manage atechnical utility process. This is generally achievedthrough computerized processing, the application’sinteraction with the power system, and communica-tions with other substation resources. Automationexamples include protection, supervisory control, andvoltage control. Fully automated applications operatewithout the direct intervention of humans. Semi-auto-mated applications require some human intervention inwhat is otherwise an automated process.

Emerging from No-Man’s LandBetter than a decade ago, intelligent electronic devices(IEDs) revolutionized the collection and processing of sub-station data. Applying digital signal Processing (DSP) to thereal-time voltage and current signals of a three-phase powersystem connection, they made it possible to extract a wealthof data representing virtually every aspect of the local powersystem’s behavior.

As time passed, it became clear that the required com-panion communications architecture would be longer incoming. The potential value of integrated IEDs was largelystranded by the limited capabilities available from tradition-al communications practice, originally designed for supervi-sory control and data acquisition (SCADA). Naturally,potential applications requiring communications supportwith higher performance, tighter timing, and peer-to-peer

figure 1. Site selected for the Bradley Substation (Site 1).

SITE 1 Selected for Bradley(Refer to Map, Next Sheet)

Original Boundary

Modified Boundary

161 kV Transmission

500 kV Transmission

Existing Transmission

Parcel Boundary

SITE 1: Note thatlines show smallerthan in legend.

may/june 2007 IEEE power & energy magazine

delivery have been most affected. But the IEC 61850 com-munications standard is now available, supported by a grow-ing number of IED products.

The Bradley Project’s mission is to 1) design, implement,and prove a broader, coherent, and synergistic technologyinfrastructure around the IEC 61850 cornerstone and 2)realign existing TVA practices to that infrastructure, enablingadvanced substation automation capabilities and removingcostly bottlenecks.

The Bradley Project ObjectivesThe following are specific Bradley Project objectives, as theyrelate to transformation of TVA’s substation practice:

1) The project shall follow and improve on the EPRIreport titled: Guidelines for Implementing SubstationAutomation using IEC 61850.

2) The new practice must produce an application environ-ment that is open, interoperable, capable and timely (ina performance sense), secure, flexible, and economical-ly viable. The latter quality is especially important, andwe will examine it in more detail.

3) A number of targeted applications must be successfullyaccommodated. Some are new for TVA and have notbeen feasible using traditional practice. The others willrequire a serious departure from past practice. Theseapplications are listed in a following section. Some

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figure 2. Map showing Site 1, selected for the Bradley Substation.

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applications (e.g., protection) may best be implement-ed as distributed applications, partitioned and distrib-uted among two or more IEDs in the substation.Distributed applications will be coordinated via inter-locks, implemented as “virtual connections” over thenetwork, using generic object-oriented substation event(GOOSE) messages.

4) The targeted applications must share a common tech-nology infrastructure. Separate infrastructures for dif-ferent applications are not acceptable, although notevery application may need to use all aspects of thecommon infrastructure. Separate infrastructures aremore expensive to build and maintain, they inhibit inte-gration, and they lack the flexibility to accommodatechanging needs.

5) The new practice must accommodate IEDs from multi-ple suppliers. TVA wants the latitude to select the bestproduct available for each system role.

6) The project must produce a workable, economicallyfeasible substation practice that is directly reusable atother sites, whether new sites or sites to be refurbished.

7) The substation configuration language (SCL) of IEC61850 must be fully supported for all IEDs and the sub-station at large. IED configuration is currently verylabor intensive, involving a number of differentapproaches of varying sophistication and ease-of-use. Alarge portion of the value provided by the IEC 61850standard resides with its SCL capabilities to simplifysystem and device configuration and ongoing data man-agement.

8) Convenient, effective data management proceduresmust be instituted that enable continual additions andchanges to be made to the system without disruptingoperation.

9) Existing construction, equipment location, equipmentinstallation, data integration, automation, testing, andcommissioning practices must be reoriented to takeadvantage of the communications network. Changes inpractice must achieve both lower cost and improvedcapability, relative to existing practice. One advantageexpected from the envisioned technology infrastructureis that its services should be universally availablethroughout the substation. This should allow more flexi-bility as to where equipment is located, except forequipment that needs to be physically wired to compo-nents of the primary infrastructure.

10) Configuration and application downloads to IEDs mustbe supported through the network, both locally andremotely. TVA really wants a network-oriented systemthat can be completely supported by personnel inremote locations, unless something breaks. Even then,they would like to understand the scope and substanceof a problem before dispatching personnel to deal withit, so that they can be prepared to do the required repairor replacement work.

11) Operation and maintenance (O&M) procedures, IEDs,and applications must allow designated devices to inter-operate in a test mode on the network while the networkand remaining IEDs are concurrently supporting normaloperational responsibilities. The design must allowthese tests to be set up, initiated, run, and interpretedfrom both local and remote locations. Tests must beable to use substituted data, either locally stored or pro-vided by the test setup.

12) The status and health of the technology infrastructuremust be adequately monitored, so that failures orincipient problems can be detected, isolated, and cor-rected. In this sense, the operation of the technologyinfrastructure needs the same attention afforded tothe power infrastructure. These two infrastructuresare interdependent and both are critically importantto the utility.

13) Contingency plans must be implemented to automatical-ly deal with IED and communication failure scenariosthat would otherwise unreasonably impair operation ofthe system. As in the UCA 2.0 pilot project completed atthe Tiptonville switching station, devices with program-mable logic will likely incorporate contingencies forcompleting certain types of operations in spite of certaintypes of communication failures or failures of otherdevices. Each IED will be continually aware of the oper-ating status of other network devices and will use thisinformation for making contingency decisions.

Project Plans This TVA initiative to transform its standard substation prac-tice is being coordinated under the Bradley Substation lineproject. As such, this effort must operate under the scheduleand milestones of the line project. Where the term “BradleyProject” is used, it is intended as an umbrella reference.

The project started building momentum in the early springof 2005. TVA contacted IED suppliers whose productsinclude both the kinds of functionality being sought and sup-port for IEC 61850 communications. The selected group ofsuppliers, which is not completely finalized, is considered tobe part of the Bradley Project team. Although TVA, assistedby consulting firms EnerNex Corporation and Utility Con-sulting International (UCI), is formulating the design planand how it will be implemented, the suppliers are consideredan important asset for dealing with unanticipated problemsand determining how their products can best be applied toachieve the project objectives.

The remainder of this article discusses how the individualproject objectives are being approached.

Universal ConstructionAs the first major consequence of these objectives, TVA willbe applying a new implementation concept called “universalconstruction.” Leveraging the flexibility offered by the net-worked communications infrastructure, it revolutionizes existing



construction practice by applying prewired, preconfiguredassembly techniques. Preselected, standardized assets are phys-ically located and integrated in a standardized manner. Equip-ment that has required half the control house in traditionalpractice will now be installed in a half-dozen open relay racks.

By design, there will now be relatively few discretewires in the substation. Their use is limited to short localinterconnections, backup TRIP/CLOSE functions for break-ers, and “A-train” transformer-differential protection. Allother connections between devices will be implemented as“virtual connections,” using the substation’s Ethernet localarea network (LAN). Expected benefits include standard-ized construction, shorter construction cycles, reduced engi-neering and labor requirements, fewer accidents, andimproved quality.

Protection, Control, Data Acquisition,and Automation In line with its project objectives, TVA will fully implementsubstation protection, control, data acquisition, and automa-tion applications via networked communications. The 40 sup-porting IEDs, supplied by four mainline manufacturers, willinclude one or more line relays, transformer protection relays,redundant devices for breaker and motor operated disconnect(MOD) applications, transformer monitoring concentrators,LTC controllers, and station computers. The capability to dis-tribute automation applications among several IEDs and tostandardize those designs for other sites will significantlyreduce recurring engineering efforts.

Together, the substation Ethernet LAN and IEC 61850standards provide an open, utility-centric communicationsenvironment, supporting capable and timely, secure, andflexible information transfers. As requirements change,applications and devices can be reconfigured via download;there is no need to modify the physical communicationsinfrastructure.

Distributed ApplicationsTVA will leverage the peer-to-peer GOOSE capabilities with-in IEC 61850 by partitioning certain applications into cooper-ative modules and distributing them among different IEDs.This will provide unprecedented flexibility to manageBradley’s information and automation environment.

Protection applications are a good example. Their job isto protect equipment in the substation (or connected to it)from scenarios that could cause damage or system insta-

bility. In recent years many relay products have appearedwith programmable logic capabilities, allowing protectionprograms to be distributed across several relays, thus phys-ically spanning areas of the facility that need to partici-pate. But to date, interlocking status exchanged betweenrelays continues to be signaled through point-to-point,hardwired contacts, supported by great lengths of stationwiring. IEC 61850 networked communications, providingnumerous “virtual connections” via GOOSE messaging,can now be used to deliver interlocking status and com-mands within 4 ms. In like manner, all sorts of “smart”controllers, IEDs, and intelligent subsystems can coopera-tively communicate over the substation LAN to achievevery sophisticated capabilities.

ApplicationsThe following are the utility applications that TVA antici-pates running at Bradley. These applications are in factimplementations of business processes that TVA believesare necessary to support its strategic substation objectives.These objectives obviously go beyond a narrower, tradi-tional view of the place substations have in supporting mis-sion-critical, mission-important, and mission-supportivegoals for the utility-at-large. Each application has a vitalbusiness purpose.

✔ SCADA: To maintain system reliability and opera-tional norms in response to failures and other adverseconditions.

✔ Protection: To prevent damage to the primary systeminfrastructure and to limit the scope and duration ofoutages.

✔ Selective data collection, reporting, and logging: Fordelivery to multiple departments on a subscriptionbasis.

✔ Synchrophasor measurements: For improving stateestimation.

✔ Transformer monitoring: To prevent catastrophic trans-former failures.

✔ Time-tagged, time-correlated, spooled event and powersystem data collection: For application performanceanalysis and troubleshooting.

✔ Integrated, automated control of breakers, LTCs,capacitor banks, and voltage regulators: For distribu-tion control and management applications.

✔ Power waveform analysis: Harmonic, distortion, andtransient analysis to improve power quality.

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The potential value of integrated IEDs was largely stranded by the limited capabilities available from traditionalcommunications practice, originally designed for SCADA.

✔ Scenario-response capabilities: Use of contingent, oper-ational responses in “smart” equipment to avoid failures.

✔ Substation HMI: For advanced O&M support and dis-placement of station panels.

Network-Based Operation and Maintenance PracticeSubstations are often in inconvenient locales, at least for peo-ple who must test and maintain them. Round trips to the sub-station represent a frustrating loss of service time andmanpower. With the advent of this new practice, TVA wantsto be able to isolate and diagnose problems remotely, so thatpersonnel pretty much know what needs to be done beforethey trek to the substation site. Likewise, they need to be ableto perform configuration and program updates for substationIEDs over the network from remote locations.

These are just a few examples of what we mean by network-based practice. Because the secondary system willbe based on IEDs that are connected to the network, there isevery expectation that O&M procedures will become alignedwith network capabilities.

Testing MethodologyWhile the network represents a host of new opportunities, itcan initially be intimidating as well. One might stand in thesubstation, faced with a problem, and think, “How do I getmy arms around this?” We will not be comfortable with net-work technology as an ally until we can conveniently manip-ulate this resource to our purposes.

As part of the Bradley Project, we have to develop a test planand a supporting methodology for determining whether func-tions, applications, and IEDs are working properly. When theyare not, which will certainly happen innumerable times while thesystem is being integrated and checked out, we need to be ableto diagnose the problem. The problem may be faulty design,failed equipment, erroneous configuration, bad setup, or a cock-pit problem. In most cases, it won’t be sufficient to run the prob-lem down to a piece of equipment; we will need to understandwhat caused the problem. No other course of action is safe dur-ing the design and integration stage. In this sense, we need test-ing tools that allow us to dig deeper than O&M personnel mayneed. So there is an expectation that these initial test tools can beadapted to derive network-based O&M test procedures.

The test methodology may be centered on the followingconcepts. This scheme, or one like it, may possibly beimplemented with the aid of an already-developed product.

✔ A laptop runs a test case program, which has a menu oftest cases available. Each test case addresses a specificfunction that can be performed over the network. A testcase will typically have a number of parameters. Theseparameters may be prepackaged in “canned” sets, or theoperator may be allowed to provide customized entries.

✔ The operator may initiate a test case from the laptop,or he may direct the laptop to initiate the requestfrom a system IED. Two or more IEDs (includingthe originator) may participate in the ensuingexchange. Initiation of the test case will result in asequence of messages, generated by the variousIEDs participating in the test. The sequence maycomprise one or more messages. For some testcases, the messages may continue indefinitely, untilthe operator terminates the test case.

✔ Once a test case is initiated, the test case program lis-tens to all messages, records them, time-tags them, anddisplays them in a way that the operator can conve-niently interpret. The test case program should flagobvious syntax problems and alert the operator if theexpected sequence of messages does not follow to con-clusion. In some instances, the data to be returned arepredictable, and the test case program can checkwhether the results are correct. In other instances (par-ticularly where the parameters have been customized),the operator must make sense of the traffic sequence.Note that the test case program should ignore any traf-fic that is not part of the test case sequence.

✔ Several test modes should be possible: “One-shotmode,” “repeat mode” (with some periodicity select-ed), and “multiple mode.” Multiple-mode would beused once the operator has confidence that individualtest cases are operating properly. In this mode, heshould be able to launch a number of different testcases to run concurrently in a repetitive mode. Theobjective here is to simulate the traffic patterns thatnaturally occur in the actual operating environment.

✔ One additional mode, “listening mode,” would also behelpful. In this mode the program is simply set up tolisten for specific traffic. Filters would be used todetermine what messages to capture.

✔ One other thing: Because data is delivered in packetsthat include encapsulating layers, the program shouldalert the operator if any of those layers appear to be cor-rupted or improperly implemented. This information


We will not be comfortable with network technology as an ally until we can conveniently manipulate thisresource to our purposes.


might come from stack notifications, since all of theselayers should be stripped when the data are delivered tothe application. Some expert help is required here tospecify a realistic approach.

Reusable PracticeThe Bradley effort will produce the foundation of a new sub-station practice, oriented around use of the IEC 61850 com-munications standard, complementary technologies, and newprocedures. It will not be complete, for there will always benew products, applications, and other variables en route to awell-established practice. But it will be coherent and viable.It will not be missing important pieces that preclude its use.We will find that the design documents and experience origi-nating from the Bradley effort will lend themselves to reason-able reapplication at subsequent sites.

TVA has examined application of this new practice atexisting sites. Prior experience with refurbishment effortsmakes it clear that incremental improvements are veryexpensive over the long haul. There are several reasons.First, incremental improvements always have to accommo-date the infrastructure to be retained, even though the lattermay be scheduled for replacement in the next round. Thecosts associated with a zigzag course always exceed those ofa direct path, if the direct path is straightforwardly achiev-able. Budget and manpower limitations, however, are oftenoverriding considerations. Nevertheless, some in TVA havepresented a compelling case for wholesale refurbishment ofthe secondary system with the new substation practice envi-sioned in this article. The bypassed incremental expense andthe advantages gained potentially swamp the cost of doingso. The Bradley Project will no doubt go a long way towardclarifying the best approach.

ConclusionThe IEC 61850 standard provides the means to integratecommunications, information, and applications into a coher-ent, flexible, very powerful framework for the secondary sys-tem. With its deployment, more information can beexchanged and more applications can be run. And we shallsee that integrated, accessible information is truly the enablerof effective and economic substation automation.

For Further ReadingL.Anderson, K-P. Brand, and W. Wimmer, “The communicationstandard IEC 61850 supports flexible and optimized substation

automation architectures,” in Proc 2nd Int. Conf. Integrated Pro-tection, Control, Communication Experience, Benefits andTrends; October 10-12, 2001.

C. Hoga and G. Wong, “IEC 61850: Open Communica-tion in practice in substations,” in Proc. IEEE PES 2004Power Systems Conf. Exposition.

R. Mackiewicz, “The impact of standardized models, pro-gramming interfaces, and protocols on substations, in Proc.IEEE 2003 Substation Conf.

A. Apostolov, “High-speed, peer-to-peer, communica-tions-based bus protection,” in Proc. IEEE PES 2001 WinterPower Meeting.

A. Apostolov and B. Vandiver, “Functional testing of IEC61850-based IEDs and systems,” IEEE - September 2004.

B. Smith, C. McClure, and R. Ehlers, “TVA's EvolvingSubstation Integration Transmission & Distribution World;April 2006.

BiographiesMichael Ingram is the general manager of Research andDevelopment with the Tennessee Valley Authority in Chat-tanooga, Tennessee. He is responsible for research, develop-ment, and demonstration of new technologies to supportlow-cost, reliable power production, power delivery, energy uti-lization, and environmental stewardship. He is a senior memberof the IEEE Power Engineering Society, and a Registered Pro-fessional Engineer. He has authored or co-authored over 40technical papers and articles within his area. He was TVA Engi-neer of the Year and a top-ten finalist for "Federal Engineer ofthe Year" in both 2001 and 2006. He received his B.E.E. degree,with honors, from Auburn University and the M.S. degree inengineering from the University of Tennessee at Chattanooga.

Randy Ehlers is a consulting engineer for Utility DataCommunications with EnerNex Corporation in Knoxville,Tennessee. He was a lead consultant with Utility Consult-ing International (UCI) in Cupertino, California. He assistsutilities with integration and automation projects involvingadvanced communication technologies. Until 2003, Randywas the U.S. product manager for substation integrationand automation systems at Siemens. He has 30 years expe-rience in the architecture, development, and integration ofsuch products and has been awarded two computer patents.He received his B.A. and M.S.E.E. degrees from Rice Uni-versity, Houston, Texas, and M.S.C.S. degree from USC,Los Angeles, California. He has been an IEEE member formore than a decade.

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With the deployment of IEC 61850, more information can be exchanged and more applications can be run.

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Toward effective substation automation