power engineering guide edition 7 1

8/20/2019 Power Engineering Guide Edition 7 1

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Answers for energy.

siemens.com/energy

Power Engineering GuideEdition 7.1

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2/5412 Siemens Energy Sector • Power Engineering Guide • Edition 7.1

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Edition 7.1

© 2014 by Siemens AktiengesellschaftMunich and Berlin, Germany.

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3/5413Siemens Energy Sector • Power Engineering Guide • Edition 7.1

Dear reader,

This updated edition of the well-known Power Engineering Guide is a manual for everyone involved in the generation,transmission and distribution of electrical energy – from system planning, to implementation and control. Our guide isdesigned to assist and support engineers, technicians, planners and advisors, as well as students, trainees and teachersof electrical engineering and energy technology. Beyond that, we hope the Power Engineering Guide will also be usefulas a reference work for technical questions and support continuing education and training in the technical eld.

Our guide covers the entire portfolio of Siemens products for the transmission and distribution of electrical power –including high, medium and low voltage, switching substations, transformers and switchgear, and is organized by productand function. It also covers solutions in the areas of Smart Grids: energy automation, energy management and networkcommunication, as well as service and support. Key terms and abbreviations are explained in a handy appendix, andInternet addresses are provided for additional in-depth information.

Siemens AG is a global leader in electronics and electrical engineering. Siemens’ products, systems and integrated,complete solutions benet customers by meeting a wide variety of local requirements. They represent the key technologiesof the future and set global standards. All our developments and innovations – which also affect methods and processes –are distinguished by energy efciency, economy, reliability, environmental compatibility and sustainability. The portfolioincludes solutions for power transmission and distribution, for Smart Grids, for low and medium voltage as well as energyautomation.

The importance of electricity is emphasized by the rapidly increasing number of electrical applications and the fact thatdemand will continually grow in the coming decades. To help our customers master their respective challenges andachieve success and further growth, we continue to work on selectively strengthening and optimizing our portfolio.As a result, in addition to “traditional” products for power transmission and distribution, today’s portfolio includes a widerange of additional products. We offer grid operators, electricity customers, planners and builders of electrical systems theadditional benets of integrated communications and automation technology. Our spectrum of services includes theplanning, maintenance and repair of entire power supply systems.

Thanks to our vast experience in managing projects around the world, we provide power utilities, industrial companies,cities, urban planer and city hubs (airports and harbors) with cost-efcient custom-tailored solutions. Please do not hesitateto contact your local Siemens sales ofce. You will nd the contacts to Siemens in your region at www.siemens.com/energyand www.siemens.com/infrastructure-cities.

Yours,

Power Engineering Guide Editorial Team

Foreword


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Contents

5Siemens Energy Sector • Power Engineering Guide • Edition 7.1

Smart Grids and the New Age of Energy 7 1

Power Transmission and Distribution Solutions 17 2

Switchgear and Substations 81 3

Products and Devices 163 4

Transformers 257 5

Protection, Substation Automation,Power Quality and Measurements 299 6

Energy Management 425 7

Communication Network Solutionsfor Smart Grids 469 8

Power System Analysis and Planning 495 9

Services & Support 509 10

Glossary 527 11

Abbreviations, Trademarks 535 12



1 Smart Grids and the New Age of Energy

Fig. 1-1: The process of urbanization continues to accelerate. At the same time, the density and complexity of urban power supply systemsare also increasing



1

Smart Grids and the New Age of Energy

Electrical energy is the backbone of our economy, and supportsevery aspect of social and cultural life today. The comfort ofalways having electricity available is anything but guaranteed,however. We face major challenges in providing adequate powergeneration, transmission and distribution to meet the world’sneeds.

The global demand for electrical energy is steadily increasing atthe rate of approximately three percent a year, faster than thetwo percent annual increase in the global demand for primaryenergy. There are many factors contributing to this escalation,including rapid population growth and longer life spans. Theprocess of urbanization continues to accelerate, and growingamounts of electricity must be transported to heavily populatedareas, usually over long distances. At the same time, the densityand complexity of urban power supply systems are alsoincreasing (g. 1-1).

Fossil fuels, on the other hand, are becoming more scarce, andexploration and production of oil and gas are becoming moreexpensive. To slow the threat of climate change we must reduceour CO 2 emissions worldwide; for power supply systems, thismeans increased integration of renewable energy sources suchas hydro, wind and solar power. At the same time, it also meansboosting the energy efciency of power supply systems, so thatthey contribute to our environmental and climate protectionefforts, and help keep energy costs under control. The growinginternational trade in energy, fueled by the liberalization ofenergy markets, and the integration of power grids across regionsrequires investment in more transmission power supply systemsto ensure system stability and guarantee power supplies.

To meet all these challenges, an intelligent and exible systeminfrastructure, smart generation, and smart buildings are essen-tial. Achieving this will require a fundamental shift from thetraditional unidirectional ow of energy and communication toa bidirectional power ow (g. 1-2). In traditional power supplysystems, power generation follows the load – but in the future,power consumption will follow generation rather than the otherway around.

Power supply systems of today and tomorrow must integrateevery type of power generation to bridge the increasing dis-tances between power generation – offshore wind farms, forexample – and the consumer.

The objectives set for Smart Grids are as diverse as they areexciting and ambitious. Instead of overloads, bottlenecks andblackouts, Smart Grids will ensure the reliability, sustainabilityand efciency of power supplies. Information and communica-tion systems within the network will be systematically expanded




Fig. 1-2: The Power Matrix: The energy system is being t ransformed. Distributed power generation is growing – increasing the system’scomplexity. The energy chain has evolved into a multi-faceted system with countless new participants – the power matrix. It reectsthe reality of the energy system. Individual power matrices are appearing in each country and region – depending on the specicsituation, challenges and goals. Siemens knows the markets and needs of its customers, and offers innovative and sustainablesolutions in all parts of the power matrix

Fig. 1-3: A Smart Grid ensures that renewable energy sources can be better integrated into the system thanks to a two-way ow of energyand a bidirectional ow of communication data. Whereas the generation of power in conventional power supply systems depends onconsumption levels, a Smart Grid is also able to control consumption – depending on the availability of electrical power in the grid




1Transmission Systems (FACTS) address the greatest challenges inpower transmission.

FACTS devices can signicantly increase the power transmissioncapacity of existing alternating current (AC) systems and extendmaximum AC transmission distances by balancing the variablereactive power demand of the system. Reactive power compen-sation is used to control AC voltage, increase system stability,and reduce power transmission losses.

State-of-the-art FACTS devices include Fixed Series Compensators(FSC) and Thyristor Controlled Series Compensators (TCSC), orStatic VAR Compensators (SVC) for dynamic shunt compensa-tion. The latest generation of Siemens SVC devices is called SVCPLUS. These are highly standardized compact devices that caneasily be implemented in demanding network environments; forexample, to allow connection of large offshore wind farms.

AC technology has proven very effective in the generation,transmission and distribution of electrical power. Nevertheless,there are tasks that cannot be performed economically or withtechnical precision using AC. These include power transmissionover very long distances, as well as between networks operatingasynchronously or at different frequencies. In contrast, a uniquefeature of HVDC systems is their ability to feed power into gridsthat cannot tolerate additional increases in short-circuit currents.

The transmission capacity of a single HVDC transmission systemhas recently been extended by the Siemens Ultra High VoltageDirect Current transmission system (UHVDC). With a capacity ofmore than seven gigawatts and low rate of loss, UHVDC trans-mission is the best way to ensure highly efcient power trans-mission of 2,000 kilometers or more. Electrical Super Gridsbased on UHVDC transmission can interconnect regions acrossclimate and time zones, allowing seasonal changes, time of dayand geographical features to be used to maximum advantage.

Siemens’ most recent development in HVDC transmission iscalled HVDC PLUS. Its key component is an innovative ModularMultilevel Converter (MMC) that operates virtually free of har-monics. HVDC PLUS converter stations are highly compactbecause there is no need for complex lter branches. Thisfeature makes HVDC PLUS perfectly suited for installation onoffshore platforms; for example, to connect offshore windfarms.

See section 2.2, page 23 (HVDC), andsection 2.3, page 32 (FACTS).

Bulk renewable integrationIn order to begin fullling the climate protection requirementsof 2020, we need to use energy efciently and reduce CO 2 emissions. Power generation needs to change accordingly.Large power plants will continue to ensure basic supplies, butthere will also be renewable energy sources that uctuatelocally depending on weather and other conditions.

and homogenized. Automation will increase considerably, andappropriately equipped smart substations will help reduce thecost and labor intensity of planning and operation. Ongoing,comprehensive monitoring will improve the way that plants andthe grid are run.

Distributed power generation and storage units will be com-bined into virtual power plants so they can also participate in thedevelopment of the market. Susceptibility to failure will beconsiderably reduced by “self-healing” systems that manage andredundantly compensate for faults at the local level. Consumerswill participate as end customers through smart meters thatoffer them better control of their own consumption, and this willmake load management easier because peak loads can beavoided through price benets. The potential of Smart Grids isenormous, and includes the use of buildings and electric vehi-cles linked into the network as controllable power consumers,generation, and even storage units.

Information and communication technology forms the cruciallinks between power generation, transmission, distribution andconsumption. The Smart Grid will create consistent structures,optimize power generation, and balance uctuating powerproduction with consumption (g. 1-3).

Siemens plays a leading role in the creation and expansion ofSmart Grids. Not only is Siemens uniquely positioned to trans-mitt and distribute power, Siemens is also the world marketleader in energy automation, which plays a decisive role in thecreation of Smart Grids.

Network planningBuilding Smart Grids is a highly complex task that begins witha detailed quantitative assessment of the system requirements,denition of actual targets and their required performancelevels, and specication of system concepts and equipment.Further, a comprehensive strategy for building Smart Gridsis necessary – not only for the power supply system, but also forother infrastructures and their interactions.

The foundation for designing an efcient Smart Grid is a detailedanalysis of the system’s required performance. This is the keytask for strategic network planning. Keeping a rigorous focus onthe system as a whole ensures that the architecture and congu-ration deliver the necessary performance levels, and meet otherrequirements as well. A state-of-the-art solution will integratethe most innovative technologies for power generation, trans-mission, distribution and consumption, while taking intoaccount each system’s individual history and current condition.In most cases, the transition from today’s power supply systemto the future Smart Grid cannot be made in one step; instead itrequires step-by-step modication plans.

See chapter 9, page 496.

Power electronics (HVDC / FACTS)Siemens power electronic solutions for High Voltage DirectCurrent transmission (HVDC) and Flexible Alternating Current




Energy Management System (EMS)At power plants, the focus is on ensuring reliable supply, usinggeneration resources efciently, and reducing t ransmissionlosses. An Energy Management System (EMS) handles these bybalancing the demands of the transmission system, generatingunits, and consumption. Intelligent Alarm Processors (IAPs)reduce the critical time needed to analyze faults in the grid andtake corrective action, as well as the risk of incorrect analysis.Innovative Voltage Stability Analysis (VSA) applications runningautomatically and independently alert the operator beforecritical situations that jeopardize static system voltage stabilityoccur, giving the operator time to take preventive action ratherthan having to react under stress. Increased grid reliability isprovided by Optimal Power Flow (OPF) applications that continu-ously work to keep the system’s voltage level high, and eliminateinvalid voltage conditions. Any control measures that must betaken can be automatically executed in a closed-loop-controlprocedure.

Using the most efcient resources is a challenge under today’smore stringent environmental restrictions, increasingly competi-tive markets, and growing contractual complexity. An integratedset of closely interacting applications – ranging from backofce-based, year-ahead resource optimization and maintenanceplanning to week- or day-ahead unit commitment and hydro-

scheduling to online closed-loop control of generating units –ensures maximum efciency grounded in powerful optimizationalgorithms and models. Security Constrained Unit Commitment(SCUC) has become the essential application for managing theworld’s most complex energy market in California at CaliforniaISO. SCUC increases grid and market efciency, reduces barriersto alternative power resources like demand-response and greengeneration, and gives the operators new tools for managingtransmission bottlenecks and dispatching the lowest-cost powerplants.


Smart substation automation and protectionThe automation and protection of substations must be enhancedto securely meet the extended requirements of future SmartGrids. The substation is in the process of becoming a node onthe utility IT network for all information from the distributionsubstation to the customer. For example, data from the feederautomation units, power quality, meters, decentralized energyresources and home automation systems will be collected andanalyzed to improve the system. Besides the new Smart Gridchallenges, the usual tasks of protection, control and automa-tion have to remain as reliable and efcient as ever. The objec-tives for substations are beginning to cross departmental bound-

M3~

HV MV LVOur solutions integrateall voltage levels and allnecessary informationfrom the energy supplyenviroment in one system.

Control room HMI

Energy automation system

Server 1 Server 2

HMI HMI

GPS

Master clock

Corporate

network

HV switchgear MV switchgear LV compartments

FirewallRouter

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Fig. 1-4: Siemens smart substation automation systems




1aries, encompassing operations, maintenance and securityrequirements. Smart substation solutions and their individualcomponents should be designed with this overarching vision andframework in mind. The use of intelligent feeder devices, anopen IEC 61850 communication architecture, powerful substa-tion computers, equipment knowledge modules and localstorage all support this approach. The automated substation forSmart Grids must integrate all aspects of intelligence, fromprotection, automation and remote control to operational safetyand advanced data collection. Going beyond the traditionalconcept of substation control and protection, the new auto-mated substation must reect the point of view of operators andmaintenance personnel to become a best-in-class system that issimple both to operate and maintain. Smart substation automa-tion ensures rapid and – more importantly – correct responses tounpredictable system events. The ability to reliably supplyelectrical power on demand can only be guaranteed by consid-ering the power supply system in its entirety (g. 1-4).

Smart substation automation systems from Siemens suppor t thefollowing goals:• Secure and reliable power supply• Guaranteed high levels of protection for facilities and people• Reduction of manual interactions to enhance rapid self-healing

operations• Implementation of intelligent remote error monitoring,

detection, reporting• Enabling condition-based predictive maintenance• Support for engineering and testing through plug-and-play

functionality• Proactively distributing substation information to all relevant

stakeholders• Reduced costs for installation and maintenance.

Siemens’ smart substation automation systems are alwayscustomized to meet each customer’s specic requirements. Theuse of standard components allows the system to scale in everyrespect. Siemens solutions offer a fully integrated and fullyautomated way to operate substations under normal and emer-gency conditions. The system is exible and open for futuremodications, making it easy to expand the substation whileallowing the addition of new Smart Grid functions.


Integrated Substation Condition Monitoring (ISCM)Integrated Substation Condition Monitoring (ISCM) is a modularsystem for monitoring all relevant substation components, fromthe transformer and switchgear to the overhead line and cable.Based on known, proven telecontrol units and subs tation auto-mation devices, ISCM provides a comprehensive solution per-fectly suited to substation environments. It integrates seamlesslyinto the existing communication infrastructure so that moni-toring information from the station and the control center isdisplayed.

See section 10.1.3, page 514.

Communication solutionsThe new Age of Electricity is characterized by a mix of bothcentral and decentralized power generation, which requiresbidirectional energy ows – including power from smart build-ings and residential areas where consumers are becoming“prosumers.” A key prerequisite for this paradigm shift is a homo-geneous, end-to-end communication network that providessufcient bandwidth between all grid elements.

Telecommunication systems for power grid transmission havea long history in the utility industry. In today’s transmissiongrids, almost all substations are integrated into a communica-tion network that allows online monitoring and controlling by anEnergy Management System (EMS).

In a distribution grid, the situation is quite dif ferent. Whereashigh-voltage substations are often equipped with digital com-munication, the communication infrastructure at lower distribu-tion levels is weak. In most countries, fewer than ten percent oftransformer substations and ring-main units (RMUs) are moni-tored and controlled remotely.

Communication technologies have continued to develop rapidlyover the past few years, and the Ethernet has become theestablished standard in the power supply sector. Internationalcommunication standards like IEC 61850 will further simplify theexchange of data between dif ferent communication partners.Serial interfaces will, however, continue to play a role in thefuture for small systems.

Because of the deregulation of energy markets, unbundling ofvertically integrated structures, sharp increases in decentralizedpower production, and growing need for Smart Grid solutions,the demand for communications is rapidly increasing. And thisapplies not just to higher bandwidths, but also to new SmartGrid applications, such as the integration of RMUs and privatehouseholds into power utilities.

For these complex communication requirements, Siemens offerscustomized, rugged communication network solutions forber optic, power line and wireless infrastructures based onenergy industry standards.

An important element in creating and operating Smart Grids iscomprehensive, consistent communication using sufcientbandwidth and devices with IP/Ethernet capability. Networks ofthis kind must eventually extend all the way to individual con-sumers, who will be integrated into them using smart metering.Consistent end-to-end communication helps meet the require-ment for online monitoring of all grid components and, amongother things, creates opportunities to develop new businessmodels for smart metering and integrating dis tributed powergeneration.





Advanced Distribution Management System (ADMS)Energy distribution systems become increasingly complex dueto the integration of distributed energy resources and storage,smart metering, and demand response. In combination withincreased grid automation, this leads to inundating util ities’systems with data that needs to be intelligently managed. At thesame time, utilities are under growing regulatory and customerpressure to maximize grid utilization and provide reliability at alltimes.

Catering to the next era of d istribution control systems, theADMS integrates three core components Distribution SCADA,OM, and Advanced Fault and Network Analysis, operated undera Common User Environment. It enables the user to• Monitor, control and optimize the secure operation of the

distribution network and• Efciently manage day-to-day maintenance efforts while

guiding operators during critical periods such as storms andoutage related restoration activities.

ADMS integrates the intelligent use of smart meter informationand regulating capabilities for distributed resources at the sametime, thus providing a solid foundation for the management ofthe emerging Smart Grid.

See section 7.2, page 443.

Distribution automation and protectionThe prerequisite for comprehensive automation and protectiondesign is determining the required levels of automation andfunctionality for distribution substations and RMUs. This coulddiffer among the RMUs in one distribution grid or in the same

feeder because of different primary equipment or communica-tion availability. However, with or without limited communica-tion access, a certain level of automation and Smart Grid func-tionality can still be realized, as can a mix of functions in onefeeder automation system. The following levels of distributionautomation can serve as a roadmap for grid upgrades movingtoward the implementation of a Smart Grid:

Local Automation (without communication)• Sectionalizer (automated fault restoration by using switching

sequences)• Voltage regulator (automated voltage regulation for long

feeders)• Recloser controller (auto reclose circuit-breaker for overhead

lines)

Monitoring only (one-way communication to distributionsubstation or control center)• Messaging box (for example, short-circuit indicators with

one-way communication to distribution substation or controlcenter for fast fault location)

Control, monitoring and automation (two-way communicationto distribution substation or control center)• Distribution Automation RTU (DA-RTU) with powerful

communication and automation features applicable toSmart Grid functions, for instance:– Automated self-healing routines– Node station for power quality applications– Data concentrator for smart metering systems– Node station for decentralized power generation– Node station for demand-response applications

Protection, control, monitoring and automation ( two-waycommunication to distribution substation or control center)• Recloser controller for overhead lines, plus auto-reclose

breaker with enhanced protection functionality and advancedcommunication and automation features

To fulll all these requirements in a Smart Grid feeder automationsystem, a modular approach to protection, monitoring, automa-tion and communication equipment is needed. Siemens offers acomplete portfolio for each level of Smart Grid application:• Robust primary and secondary equipment to withstand tough

outdoor conditions• Flexible IO modules adapted to the requirements of the

specic RMU type, for example, for direct output to motor-driven switches or input from RMU sensors

• Optimized CPUs with advanced automation and protectionfunc tions to secure a safe and reliable power supply, with auto-mated system recovery functions and convenient remote access

• Reliable (emergency) power supplies for all components in theRMU, for example, to operate the switchgear motor drive, torun a heating system for outdoor application, or to power thecontroller and communication units

• Future-oriented, fast communication via different infrastruc-tures, for example, GPRS-/GSM modem, ber optic, and powerline carrier

Fig. 1-5: Spectrum Power ADMS combines SCADA, outagemanagement, and fault and network analysis functions forthe rst time on a software platform under a common userinterface




1• Multiple communication protocols like IEC61850 and DNPi to

connect the RMU with the distribution subs tation, controlcenter, or end-user applications

• Modular, sustainable controller functions to fulll specic SmartGrid requirements like fault detection and isolation, automaticreclosing functions, voltage or load-ow regulation, and more

• A user-friendly, powerful engineering tool with seamlessintegration in the overall engineering process of the distributionautomation system to enable maximum re-use of data

• Open interfaces for all system components, enabling theintegration of other applications; in other words, a system thatis equipped for future Smart Grid modications

To manage these tasks with a global perspective, it is crucial tofully understand the overall structure of distribution grids:primary and secondary equipment, voltage levels (from highvoltage via medium voltage to low voltage), indoor and outdoorapplications, and multiple local regulations and standards. A bigadvantage derives from the use of exible components in thesame system family for the diverse feeder automation applica-tions. Siemens provides this and more with our comprehensiveAdvanced Energy Automation portfolio, which transforms aSmart Grid vision into reality.

Distributed Energy Resources (DER)The integration of distributed energy resources (DER) calls for acompletely new concept: the virtual power plant. A virtualpower plant connects many small plants that participate in theenergy market in a completely new way. It makes it possible touse sales channels that otherwise would not be available to theoperators of individual plants. Linked together in the network,the plants can be operated even more efciently – and thereforemore economically – than before, beneting the operators ofdecentralized generating facilities.

In the virtual power plant, decentralized energy managementand communication with the generating facilities play a specialrole, and thanks to the Siemens products Decentralized EnergyManagement System (DEMS) and DER Controller, are optimallysupported. The centerpiece is DEMS, which enables the intelli-gent, economical and environmentally friendly linkage of decen-tralized energy sources. The DER Controller facilitates communi-cations, and is specically tailored to the requirements ofdecentralized energy sources.


Decentralized Energy Management System (DEMS)DEMS, the core of the virtual power plant, is equally appropriatefor utilities, industrial operations, operators of functional build-ings, energy self-sufcient communities, regions and energyservice providers. DEMS uses three tools – predictions, opera-tional planning and real-time optimization – to optimize power.The prediction tool anticipates electrical and heat loads; forexample, as a function of the weather and the time of day.Predicting generation from renewable energy sources is alsoimportant, and is based on weather forecasts and the uniquecharacteristics of the plants. Short-term planning to optimizeoperating costs of all installed equipment must comply withtechnical and contractually specied background conditionsevery 15 minutes for a maximum of one week in advance. Thecalculated plan minimizes the costs of generation and operation,while DEMS also manages cost efciency and environmentalconsiderations.


Fig. 1-6: In vitual power plants, decentralized energy management and communication with generating facilities pl ay a special role, andthanks to the Siemens products DEMS and DER controller, are optimally supported




Smart metering solutionsSmart metering connects consumers to the Smart Grid throughbi-directional communication, thus underpinning the newrelationship between consumer and producer. The Smart Grid isalready radically changing the gas, water and electricity land-scape. More than ever, regulatory requirements, technologyadvances, and heightened expectations of system operators aredriving the integration of communicating hardware and systems,leading to an explosion of data. Siemens smart metering solu-tions are making the benets of the Smart Grid tangible today.Siemens’ class-leading technology and services are deployedand proven in markets around the world. There are a numberof smart metering solutions and services on the market andpotentially, one could end up using multiple agents to supportyour metering needs making a complex solution even moreconfusing. Siemens removes this complexity. Its end-to-enddomain knowledge and expertise spanning the entire energyconversion chain is our main differentiator. Siemens offersa comprehensive line of products, accredited solutions, andservices, supplying complete solution packages for smartmetering. Siemens can supply the meter, retrieve, validate andpresent the data, and open up useful energy managementopportunities, taking responsibility for the whole operation,from start to nish.

Siemens’ smart metering portfolio includes:• Metering hardware and system components, including single-

phase and three-phase AMI meters• Automated metering and information system (AMIS)• Grid appl ication platform EnergyIP• Smart prepayment metering solution• Solutions to combat non-technical loss (MECE)• Grid metering solutions• Commercial and industrial metering solutions• Smart multi-dwelling unit solution, and• End-to-end smart metering design, implementation and

integration services

Siemens’ grid application platform EnergyIP helps leading elec-tric, gas and water utilities worldwide modernize the speed ofprocessing sensor data. Siemens transforms business operationswith a software application approach that delivers accuratebilling, proactive outage management, revenue protection,customer engagement, and more. Deployed at over 50 utilitiesworldwide, our solutions empower utilities to rapidly deploysoftware and communications systems in order to effectivelyscale and maximize operational efciency.

See section 10.3, page 521.

There is no doubt that the future belongs to the Smart Grid, andthat power generation will change signicantly by the time itbecomes a reality. Large power plants will continue to ensurethe basic supply, but there will also be renewable energysources, causing uctuations in the grid. In the not too distantfuture, exible intermediate storage of temporary excess powerin the grid will be possible using electric vehicles and stationarystorage units. Sensors and smart meters will switch these units

on or off, ensuring efcient load management. From generatinglarge offshore wind farms to delivering smart metering inhomes, Siemens is one of the worldwide leading providers ofproducts, systems, technology and solutions for Smart Grids.




1



2

Power Transmission and Distribution Solutions

2.1 Overview of Technologies and Services 182.1.1 Solutions for Smart and Super Grids

with HVDC and FACTS 182.1.2 AC/DC Transmission and Distribution 182.1.3 Totally Integrated Power

We Bring Power to the Point –Safely and Reliably 20

2.1.4 Consultant Support for Totally Integrated Power 212.1.5 Managing Entire Projects 222.1.6 Partners throughout the System Life Cycle 22

2.2 High-Voltage Direct-Current Transmission 232.2.1 Siemens HVDC Technologies 232.2.2 Main Types of HVDC Schemes 232.2.3 LCC HVDC – The “Classical” Solution 242.2.4 Ultra-HVDC Transmission (UHV DC) Bulk Power 252.2.5 HVDC PLUS – One Step Ahead 25

2.2.6 DC Compact Switchgear DC CS 272.2.7 Siemens HVDC Control System: Win-TDC 302.2.8 Services 31

2.3 Flexible AC Transmission Systems 322.3.1 Parallel Compensation 322.3.2 Series Compensation 342.3.3 Synchronous Condenser 35

2.4 Power Transmission Lines 362.4.1 Gas-Insulated Transmission Lines 362.4.2 High-Voltage Power Cables 412.4.3 Overhead Lines 46

2.5 Grid Access Solutionsfor Decentralized Power Generation 60

2.5.1 References 62

2.6 SIESTORAGE 662.6.1 The Modular Energy Storage System

for a Reliable Power Supply 662.6.2 Spot-on for a Wide Range of Applications 682.6.3 High Power Availability and Reliability 692.6.4 Benets of Comprehensive Competence 71

2.7 E-Houses for Power Distribution 72

2.7.1 Plug-and-Play Power Supply Solution 722.7.2 Cost-Effective Solution 732.7.3 Time-Efcient Solution 732.7.4 Flexible and Optimized Design 732.7.5 One-Stop Solution 75

2.8 Microgrids – The Next Step towardsan Efcient Use of Distributed Resources 76

2.8.1 Operation, Monitoring, Administration,Planning – All Under One Roof 76

2.8.2 Microgrid Market Segments 772.8.3 Siemens Microgrid Management Systems 79



2 Power Transmission and Distribution Solutions

• Reliable: assuring and improving security and quality of supply• Economic: providing best value through innovation, efcient

energy management and “level playing eld” competition andregulation

Smart Grids will help achieve a sustainable development. It isworthwhile mentioning that the Smart Grid vision is in the sameway applicable to the system developments in other regions of theworld. Smart Grids will help achieve a sustainable development.

An increasingly liberalized market will encourage trading oppor-tunities to be identied and developed. Smart Grids are a neces-sary response to the environmental, social and political demandsplaced on energy supply.

2.1.2 AC/DC Transmission andDistribution

HVDC and FACTSToday’s power transmission systems have the task of transmittingpower from point A to point B reliably, safely and efciently. It isalso necessary to transmit power in a manner that is not harmfulto the environment. Siemens offers comprehensive solutions,technical expertise and worldwide experience to help systemoperators meet these challenges.

For each application and technical transmission stage, Siemensoffers optimized solutions with HVDC transmission or FACTS forthe most efcient operation of power systems.

Typical applications for FACTS include fast voltage control,increased transmission capacity over long lines, power owcontrol in meshed systems, and power oscillation damping. WithFACTS, more power can be transmitted within the power system(section 2.3). When technical or economical feasibility of con-ventional three-phase technology reaches its limit, HVDC will bethe solution (g. 2.1-2). Its main application areas are econom-ical transmission of bulk power over long distances and intercon-nection of asynchronous power grids. Siemens’ latest innovationin high-voltage direct-current technology is HVDC PLUS. Theadvantages of the new system, which employs voltage-sourcedconverters, include a compact layout of the converter stations,and advanced control features such as independent active andreactive power control and black start capability.

2.1 Overview ofTechnologies and Services

Feeding the power generated at different locations over longdistances into power systems often calls for optimized powertransmission and distribution solutions. Despite the challenges itposes, however, interconnecting of different regions, countriesor even continents remains a viable option for providing theseareas with economical access to power (g. 2.1-1). As a solutionprovider with extensive experience in every aspect of powertransmission and distribution, Siemens has already implementeda large number of projects linking power systems or connectingdecentralized generating units to the grid. In each case, condi-tions were unique. And because Siemens strives to provide itscustomers with the most cost-efcient results, the implementedsolutions using different technologies were also unique.

With Totally Integrated Power, Siemens offers a comprehensivelow-voltage and medium-voltage por tfolio which makes powerdistribution efcient, reliable, and safe – in cities, infrastructure,buildings, and industrial plants.

2.1.1 Solutions for Smart and Super

Grids with HVDC and FACTSThe power grid of the future must be secure, cost-effective andenvironmentally compatible. The combination of these threetasks can be tackled with the help of ideas, intelligent solutionsas well as advanced technologies.

Innovative solutions with HVDC (High-Voltage Direct-CurrentTransmission) and FACTS (Flexible AC Transmission Systems)have the potential to cope with the new challenges. By means ofpower electronics, they provide features which are necessary toavoid technical problems in the power systems, they increasethe transmission capacity and system stability very efcientlyand help to prevent cascading disturbances.

The vision and enhancement strategy for the future electricitynetworks are, for example, depicted in the program for “SmartGrids”, which was developed within the European TechnologyPlatform.

Features of a future Smart Grid such as this can be outlined asfollows:• Flexible: fullling operator needs whilst responding to the

changes and challenges ahead• Accessible: granting connection access to all network users,

particularly for Renewable Energy Sources (RES) and high-efciency local generation with zero or low carbon emissions


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Power linesSince the very beginning of electric power supply, overhead lineshave constituted the most important component for transmissionand distribution systems. Their portion of the overall length ofelectric circuits depends on the voltage level and on local condi-tions and practice. When environmental or structural factors makeoverhead lines impossible, Siemens’ “underground” transmissionpath is the ideal solution. Siemens gas-insulated transmissionlines (GIL) can be an economically viable alternative to conven-tional power cables (section 2.4).

Grid accessDecentralized generating units are custom-engineered, whichinvolves reconciling contrasting parameters, such as high reli-ability, low investment costs and efcient transmission, in thebest possible solution. Specic attention is paid to intelligentlydesigning the “collection systems” at the medium-voltage level,which is followed by the high-voltage transmission systemproviding the grid access. By relying on both transmission tech-nologies, Siemens can offer AC as well as DC solutions at boththe high- and medium-voltage levels (section 2.5).

Solar powerAs an alternative power supply for rural electrication, Siemensintegrates solar power in the low-voltage distribution system forprivate consumers, as stand-alone systems or even with gridconnection (section 2.6).

Investmentcosts Total

ACcostsBreak-even distance

DC terminal costs

AC terminal costs –including grid transformers

TotalDCcosts

DC linecosts

AC linecosts

Transmission distance

* SSC = Series or shunt compensation of AC lines – required for each section of the line

2xSSC*

2xSSC*

Fig. 2.1-2: AC versus DC transmission cost over distance.The break-even distance amounts typically to 600 kmfor a power transmission of 1,000 MW

P

P

P

Symbols: TPSC/TCSC DC transmissionand interconnection

North system50 Hz

South system60 Hz

Central system60 Hz

Clean andlow-costenergy

Industrialenergy supply

Tariff

Tariff

Powerexchange

Power exchange– Asynchronous networks

Avoidance ofloop ows

Fault- CurrentLimiter

Cleanenergy

SVC FSC B2B as GPFC HVDC PLUS

SVC PLUS

Bulk power andlong distance

F C L

Submarinecable links

Fig. 2.1-1: Power transmission and distribution solutions

2.1 Overview of Technologies and Services


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20 Siemens Energy Sector • Power Engineering Guide • Edition 7.1

2.1.3 Totally Integrated Power We Bring Power to the Point –Safely and Reliably

Efcient, reliable, safe: These are the demands placed on electri-cation and especially power distribution (g. 2.1-3). And ouranswer – for all application areas of the energy system – isTotally Integrated Power (TIP). It is based on our comprehensiverange of products, systems and solutions for low and mediumvoltage, rounded out by our support throughout the entirelifecycle (g. 2.1-4) – from planning with our own software toolsto installation, operation and services.

Smart interfaces allow linking to industrial or building automa-tion (g. 2.1-4), making it possible to fully exploit all the optimi-zation potential of an integrated solution. This is how we pro-vide our customers around the world with answers to theirchallenges. With highly efcient, reliable and safe power distri-bution, we lay the foundation for sustainable infrastructure andcities, buildings and industrial plants. We bring power to thepoint – wherever and whenever it is needed.

Totally Integrated Power of fers more:• Consistency: For simplied plant engineering and

commissioning, as well as smooth integration into automationsolutions for building or production processes

• One-stop-shop: A reliable partner with a complete portfolio forthe entire process and lifecycle – from the initial idea to after-sales service

Fig. 2.1-3: Comprehensive answers for power dist ribution in complexenergy systems – from Siemens

Fig. 2.1-4: TIP is the perfect link to industrial and building automation

Process/Industrialautomation

Storagetechnologies

Medium-voltageswitchgear and

protection technology

Transformer

≤ 110 kV

Buildingautomation

PROFINET PROFIBUS ... Modbus

Consulting,planning

OperationOrder,delivery

Engineering Service,modernization

Installation,commissioning

Products, systems and solutions

Industrial Ethernet

Automation

Electrication

Low-voltage switchboardwith protection and

measuring technology

Low-voltagedistribution

Renewables

• Safety: A comprehensive range of protection components forpersonnel safety, and l ine and re protection, safety by meansof type testing

• Reliability: A reliable partner who works with systemoperators to develop long-lasting solutions that meet thehighest quality standards

• Efciency: Bringing power to the point means greater plantavailability and maximum energy efciency in powerdistribution

• Flexibility: End-to-end consistency and modular design ofTotally Integrated Power for any desired expansions andadaptation to future requirements

• Advanced technology: Reliable power distribution especiallyfor applications in which supply is critical, continuousrenement of the technology.


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2.1.4 Consultant Supportfor Totally Integrated Power

Comprehensive services for the planning and conceptdrafting of electric power distribution systemsExperts – the Siemens TIP Consultant Support team – helpelectrical designers in many countries nd holistic solutions forthe elds of infrastructure, building and industry – even when itcomes to critical power supply, for example, in hospitals anddata centers.

All along the various planning phases, planners have recourse,to efcient software tools, online tender specication texts, andplanning and application manuals.

The innovative SIMARIS® planning tools set standards in terms ofplanning efciency. They support the planning process whendimensioning electric power distribution systems, determiningthe equipment and systems required, and preparing tenderspecication texts. The product portfolio of devices and systemsrequired, ranging from the medium-voltage switchgear tomodular installation devices in the dis tribution board, ismapped. This enables to plan entire power distribution systemsfrom start to nish using the free-of-charge SIMARIS planningtools (g. 2.1-5).

Siemens also provides qualied support for creating technicalspecication lists in the form of online tender specication textswithin the framework of Totally Integrated Power. The fullyintegrated Siemens portfolio for electric power dis tribution canbe found there. The clear tree structure in combination with asearch function helps users nd texts for the desired products.The text modules that were selected can be compiled in custom-ized specications (g. 2.1-6).

The planning and application manuals will help you familiarizeyourself with the technical background when planning powersupply systems, and implementing it in product and systemssolutions. In addition to the topical introduction provided by theplanning manuals, the application manuals include solutioncriteria and approaches for planning power dist ribution toindustry-specic buildings that meet our customers’ needs.Typical congurations and boundary conditions are presented inthe form of examples, which are then turned into feasibleconcepts for the relevant building types, using specic productsand system proposals. All manuals can be downloaded from ourwebsite as PDFs (g. 2.1-7).

For further information:www.siemens.com/simariswww.siemens.com/specificationswww.siemens.com/tip-cs/planningmanuals

Fig. 2.1-5: The SIMARIS planning tools – easy, fast and safe planningof electric power distribution

Fig. 2.1-7: Planning and application manuals impart specializedand up-to-date knowledge

Fig. 2.1-6: Text modules for tender specications covering allSiemens products for electric power distribution


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For further information:www.siemens.com/energy/power-transmission-solutionswww.siemens.com/energy/hvdc-facts-newsletter

Fig. 2.1-8: Siemens services for the entire system life cycle

Development phase3 years

Financial close

Implementation phase3 years

Start ofcommercial use

Operation25 years

Maintenance and after-sales services

Overall project management

Engineering• Basic design• Conceptual design• Detailed design

Procurement• Manufacturing• Global sourcing• Local sourcing

Construction• Erection• Commissioning• Training

Technical advice• Feasibility study

Performances values:LossesReliabilityAvailability

• Design transmissionsystem

Financial advice• Economical assessment• Feasibility study

FlexibilityRentabilityEstimates

• Bankability

Capabilities for project development, implementation and operation

2.1.5 Managing Entire Projects

Project managementSupplying power is more than just combining a number ofindividual components. It calls for large-scale projects, such astransmission systems or industrial complexes, especially incountries where the demand for power is growing at an acceler-ated pace. The best partner to handle such large projects is anexpert who can carefully analyze the demand, take an integratedapproach to project planning, and consider all the general condi-tions. A qualied project partner is one that can provide high-quality components and services for both power transmissiontasks and power system management. Such a partner also canensure that the systems are installed expertly.

Turnkey solutionsSiemens’ many years of experience allow to offer turnkeypower transmission solutions that are tailored to individualrequirements. Siemens supplies all components, includingpower plants, AC or DC transmission systems, and high-voltageinterconnected power systems with high, medium and lowvoltage that nally reach the individual customers. What makesthese turnkey solutions so attractive is that one par ty is respon-sible for coordinating the entire project, thereby reducing thenumber of interfaces between system operator and supplier to abare minimum. Turnkey projects also reduce the operator‘s ownshare in project risks, since Siemens is responsible for deliveringa system that is ready for operation.

Engineering, procurement, production and constructionIn addition to comprehensive planning and management ser-vices, engineering is one of Siemens’ special strengths. Siemenscan produce or procure all necessary components and performall construction work up to testing, commissioning and puttingan entire system into operation. With Siemens as a partner,companies can benet from Siemens’ extensive manufacturingexpertise and from the work of experienced Siemens engineerswho have already participated in a wide range of projects world-wide. Working on this basis, Siemens can provide the besttechnology for projects based on proprietary Siemens compo-nents and additional hardware purchased from reputable ven-dors. Siemens experts have the important task of determiningwhich of the various technical options are best suited for imple-menting the project. They consider transmission capacity,transmission efciency and the length of the transmission line,and after the best technical solution has been determined, theyassess its long-term cost efciency for the operator. Only thencan the actual implementation begin for installation and on-timecommissioning.

MaintenanceSystems will operate at their best when equipment lasts a longtime and provides continuous trouble-free operation. TheSiemens maintenance service ensures that all components arealways running safely and reliably. Siemens continuously main-tains operator systems through regular inspections including allswitchgear and secondary technology. If a malfunction occursduring operation, Siemens is immediately on the job; support is

available 24 hours a day, 365 days a year. And with the increaseduse of state-of-the-art online monitoring and remote diagnosissystems, Siemens offers additional possibilities for keepingoperating costs to a minimum.

Optimization and modernizationTechnological evolution leads to equipments and systems whichare continuously improving. Siemens offers retrot and upgradeservices for existing schemes. This fast and economical solutionallows customers to invest their capital wisely and take fulladvantage of Siemens’ experience in adapting older systemsto new technical standards.

2.1.6 Partners throughout the SystemLife CycleSiemens is with system operators every step of the way to helpthem develop their projects, to create nancing solutions and toprovide project management (g. 2.1-8), and supports thembeyond engineering, production and construction. This supportcontinues as the system is commissioned, as customers needmaintenance services and even when it is time to modernize.The partnership between Siemens and the system operatorsdoes not stop when a turnkey job is nished: Siemens accompa-nies the system operators throughout the entire life cycle oftheir systems, offering a wide range of services with productsof the highest quality that are always based on the most durabletechnologies.


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2.2 High-Voltage Direct-Current Transmission

Siemens HVDC transmission is used when technical and/oreconomical feasibility of conventional high-voltage AC transmis-sion technology have reached their limits. The limits are over-come by the basic operation principle of an HVDC system, whichis the conversion of AC into DC and viceversa by means of highpower converters.

Featuring its fast and precise controllability, a Siemens HVDC canserve the following purposes:• Transmission of power via very long overhead lines or via long

cables where an AC transmission scheme is not economical oreven not possible

• Transmission of power between asynchronous systems• Exact control of power ow in either direction• Enhancement of AC system stability• Reactive power control and support of the AC voltage• Frequency control• Power oscillation damping.

2.2.1 Siemens HVDC Technologies

Depending on the converter type used for conversion betweenAC and DC, two technologies are available:• Line Commutated Converter technology (LCC) based on

thyristor valves• Voltage Sourced Converter technology (VSC) based on IGBT

valves, also known as HVDC PLUS.

Both technologies enable Siemens to provide attractive solutionsfor most challenging transmission tasks ranging from extra-high-voltage bulk power transmission to the connection of systems inremote locations to main grids; from long distance overhead lineor cable to interconnection of two systems at one location.

2.2.2 Main Types of HVDC Schemes

The main types of HVDC converters are distinguished by their DCcircuit arrangements (g. 2.2-1), as follows:

Back-to-back:Rectier and inverter are located in the same station. Theseconverters are mainly used:• To connect asynchronous high-voltage power systems or

systems with different frequencies• To stabilize weak AC links• To supply more active power where the AC system already is at

the limit of its short-circuit capability• For grid power ow control within synchronous AC systems.

Cable transmission:DC cables are the most feasible solution for transmitting poweracross the sea to supply islands/offshore platforms from themainland and vice versa.

Long-distance transmission:Whenever bulk power is to be transmitted over long distances,DC transmission is the more economical solution compared tohigh-voltage AC.

Back-to-backstation

AC AC

Submarine cabletransmission

Long-distanceOHL transmission

AC AC

AC AC

DC Cable

DC Line

Fig. 2.2-1: Overview of main power transmission applications withHVDC


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2.2.3 LCC HVDC –The “Classical” SolutionAfter more than 50 year’s history with Siemens constantlycontributing to its development, LCC HVDC is still the mostwidely used DC transmission technology today.

Technology

Thyristor valvesThe thyristor valves are used to perform the conversion from ACinto DC, and thus make up the central component of the HVDCconverter station. The valves are described by the followingfeatures:• Robust design• Safe with respect to re protection due to consequent use of

re-retardant, self-extinguishing material• Minimum number of electrical connections and components

avoiding potential sources of failure• Parallel cooling for the valve levels using de-ionized cooling

water for maximum utilization of the thyristors• Ear thquake-proof design as required (g. 2.2-2)• Direct Light-Triggered Thyristors (LTT) with wafer-integrated

overvoltage protection – the standard solution for transmissionratings up to 5,000 MW

• Electrically triggered thyristors for bulk power transmission upto 7,200 MW and above.

Filter technology Filters are used to balance the reactive power of HVDC andpower system and to meet high harmonic performance stan-dards.• Single-tuned, double-tuned and triple-tuned as well as high-

pass passive lters, or any combination thereof, can beinstalled depending on the specic requirements of a station

• Active AC and DC lters are available for highest harmonicperformance

• Wherever possible, identical lters are selected maintainingthe high performance even when one lter is switched off.

ApplicationsThe primary application areas for LCC HVDC are:• Economical power transmission over long distances• Interconnection of asynchronous power grids without increase

in short-circuit power• Submarine DC cable transmission• Hybrid integration of HVDC into a synchronous AC system for

stability improvement• Increase in transmission capacity by conversion of AC lines into

DC lines.

Power ratingsTypical ratings for HVDC schemes include:• Back-to-back: up to typically 600 MW• Cable transmission: up to 1,000 MW per HVDC cable• Long-distance transmission: up to typically 7,200 MW.

Fig. 2.2-3: Two times two 400 kV converter systems connected inseries form a ± 800 kV UHV DC station

Fig. 2.2-2: Earthquake-proof and re-retardant t hyristor valves in500 kV long-distance transmission in Guizho-Guangdong,China


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2.2.4 Ultra-HVDC Transmission(UHV DC) Bulk PowerUHV DC from Siemens is the answer to the increasing demandfor bulk power transmission from remote power generation tolarge load centers. After having been awarded the contract in2007, Siemens has successfully commissioned the world’s rst±800 kV UHV DC system with 5,000 MW in China SouthernPower Grid in 2010 (g. 2.2-3).

TechnologyThe high DC voltage imposes extreme requirements to theinsulation of the equipment and leads to huge physical dimen-sions (g. 2.2-4). The capability to withstand high electrical andmechanical stresses is thoroughly investigated during thedesign. All components are extensively tested to assure that theywithstand most severe operating conditions and meet highestquality standards.

The thyristor valves are equipped with either 5’’ or 6’’ thyristorsdepending on the transmission rating (g. 2.2-5).

ApplicationsUHV DC transmission is the solution for bulk power transmissionof 5,000 MW or higher over some thousand kilometers. Com-pared to a 500 kV LCC HVDC system, the Siemens 800 kV UHVDC reduces line losses by approx. 60 % – an important aspectwith respect to CO2 reduction and operational cost.

Special attention has to be paid to the corresponding AC networksthat have to supply or absorb the high amounts of electric power.

Power ratingsThe Siemens 800 kV HVDC systems are designed to transmit upto 7,200 MW over long distances.

2.2.5 HVDC PLUS – One Step Ahead

VSC technology offers unique advantages for HVDC transmissionwhich become more and more important for applications likeconnecting remote renewable energy sources, oil and gasplatforms or mines to an existing grid.

Using the latest modular IGBT (Insulated Gate Bipolar Transistor)technology in a pioneering Modular Multilevel Converter (MMC)design, Siemens engineers have developed HVDC PLUS as alandmark product in the evolution of HVDC transmission.

The high power ratings available today make HVDC PLUS increas-ingly attractive also for projects where LCC HVDC could be usedfrom a technical perspective.

FeaturesHVDC PLUS provides important technical and economicaladvantages compared to LCC:• HVDC technology in the smallest possible space:

An HVDC PLUS station does typically not require any harmonic

Fig. 2.2-5: UH voltage and power electronics – the thyristor valvesare designed to operate at 800 kV voltage level. Yunnan-Guangdong, China

Fig. 2.2-4: A 20.8 m long wall bushing is required in order to connectthe 800 kV terminal of the indoor thyristor valves to theoutdoor HVDC equipment and overhead line

Fig. 2.2-6: Converter Station of the TransBay Project close to thecity center of San Francisco. The world’s rst VSC HVDCtransmission scheme in Modular Multi-level Converter(MMC) topology


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lters (g. 2.2-6). The MMC design allows to realize nearlyperfect sinusoidal AC-side converter terminal voltages whichare virtually free from harmonics. Together with a compactdesign of the MMC, this makes HVDC PLUS perfectly suitablefor offshore platforms or stations with limited space(g. 2.2-7).

• Independence from short-circuit capacity:HVDC PLUS can operate in networks with very low short-circuitcapacity or even in isolated systems with or without owngeneration using its black-start capability.

• Unipolar DC voltageThe DC voltage polarity is xed independently from thedirection of power ow. This allows integration into multi-terminal systems or DC grids. HVDC PLUS can operate withextruded XLPE or mass-impregnated DC cables.

• Economical design and standardization:The modularly designed HVDC PLUS converter stations can beperfectly adapted to the required power rating.

• For symmetrical monopolar congurations, standard ACtransformers can be used, whereas LCC transformers requirespecial design due to additional stresses from DC voltage andharmonics.

ApplicationsHVDC PLUS can be applied in all elds of HVDC transmission –there are no technical restrictions. The advantages of HVDC PLUSwill be most apparent in circumstances that require the follow-ing capabilities:• Black start of AC networks• Operation in AC networks with low short-circuit capacity• Compact design, e. g., for offshore platforms• Operation in DC multi-terminal systems or in a DC grid.

Power ratingsThe design of HVDC PLUS is optimized for power applications inthe range from 30 MW up to 1,000 MW or higher, depending onthe DC voltage.

Topologies (g. 2.2-8)Different topologies are available in order to t best for theproject specic requirements:• Half-bridge (HB) topology

The DC voltage is always controlled in one polarity only. Such aconguration is preferred for DC circuits with pure cablecongurations. The risk of DC-side faults are small andtypically lead to a permanent shutdown of the link

• Full-bridge (FB) topologyThe DC voltage can be controlled in a wide range includingboth polarities. Such a topology is predestinated for DC circuitswith overhead lines, and provides the same features as knownfrom HVDC Classic: DC line faults (e.g. due to lightning strikes)are cleared safely by a short-time reversion of the voltage.Furthermore, operation at reduced DC voltage levels is possible,which is often specied in case of pollution problems of lineinsulators.

Fig. 2.2-7: The heart of HVDC PLUS is a modular multilevel converter(MMC) which can be scaled according to the voltage orpower requirements. Transbay Cable, USA

Fig. 2.2-8: MMC topologies: half and full bridge

Half-bridge type MMC:

The power capacitor can

be connected in onepolarity to the terminals.

Full-bridge type MMC:

The power capacitor canbe connected in eitherpolarity to the terminals.

0

0

U dc

U ac

U dc U ac

U acU dc

U acU dc

-U dc

"on" "off"

Fig. 2.2-10: Full-bridge MMC: The DC voltage is independent fromthe AC voltage and can be controlled to zero, or even beentirely reversed maintaining current control on the ACand DC sides including under shor t-circuit conditions

12

n

1

2

n

U AC

U Conv.

+ U d /2

-U d /2

0

AC and DC Voltages

Fig. 2.2-9: Half-bridge MMC: The DC voltage is always higher thanthe AC voltage

1

2

n

1

2

n

U AC

U Conv.

+ U d /2

-U d /2

0


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2.2.6 DC Compact Switchgear DC CS

Business drivers for the development of DC compactswitchgearThe changing generation and load structure in existing powergrids requires increased transmission capacity. Longer transmis-sion distances and increased loading tend to reduce the AC grid’sstatic and dynamic stability. To amend this, HVDC systems can beintegrated into existing AC grids to provide the required transmis-sion capacity, and at the same time increase grid stability.

What is more, the global trend towards decarbonization ofpower generation calls for an increased use of renewable energysources (RES). While RES like offshore wind are typically found atgreat distances from the load centers, HVDC provides an effec-tive (and in some cases the only) technical solution for powertransmission.

The compact 320 kV DC switchgear DC CS is needed for HVDCcable connections to remote offshore wind farms, as well as foronshore HVDC projects. Thanks to its compact design, the DC CShelps to reduce the HVDC system’s space requirements. Hence itis predestinated for applications where space is limited or expen-sive, e.g. offshore HVDC platforms for remote windfarms, as wellas close to city centers.

Using the DC CS outdoors even in rough climates adds to thiseffect. In the near future, DC compact switchgear and transmis-sion solutions facilitate the realization of multi-terminal arrange-ments or DC grids, backing up the existing AC networks.

Fig. 2.2-11: Standardized modules of the DC CS product line

Fig. 2.2-12: 320 kV DC switchyard in/out bay

1

1

2

2

33

4

4

5

5

Disconnector andearthing switch

Voltage and currentmeasurementInterface modules

Passive modules

Surge arrester

= 31C01= 32C01= 41C01= 42C01

-Z1

-F1

-T1

-Q51

-Q11

-Q52

-F2

-Z2


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Modular structureThe 320 kV Direct-Current Compact Switchgear (DC CS) (withoutcircuit-breaker) is developed based on proven 8DQ1 550 kV ACGIS design and a new DC insulator following the well-establishedresin-impregnated-paper design which is used in wall bushingsfor decades.

The DC CS is a highly modularized product line, with standard-ized and predened modules (g. 2.2-11) which minimize therequired interface engineering complexity between the DC CSmodules as well as interfaces to e.g. control and protectionsystems. Examples of a 320 kV converter pole feeder arrange-ments are given in g. 2.2-12 and g. 2.2-13.

The range of modules l ike 0°/90° disconnector and earthingswitch modules, 45°/90° angle modules grant exibility to adaptto complex arrangements such as designs with a single ordouble busbar.

The module catalog is completed by an RC divider for voltagemeasurement, the zero ux compensated current measurementsystem, surge arrester and compensation modules required forservice access, and both axial and lateral heat dilatation.

Application and special arrangementsDC compact switchgear can be applied at various locations withan HVDC system as displayed in g. 2.2-13. An important appli-cation option for DC CS is between the converter transformerand the converter valves. With bipolar arrangements where 2 ormore converters are arranged in a line with neutral in between,the section between the secondary connection of a convertertransformer and the respective converter valves is stressed witha DC voltage offset resulting in a mixed voltage stress AC/DCrequiring dedicated DC equipment. On the DC terminal, the DCswitchyard, transition stations (enabling compact transitionfrom cable to overhead line) along the line and nally futuremulti-terminal stations can be planned with DC CS.

The most important benet of 320 kV DC compact switchgear isits inherent size advantage compared to air-insulated DC switch-yard equipment.

Furthermore, the option for outdoor installation, even underextreme environmental conditions, is an advantage of DC CS. Iffor technical reasons, like temperature below -30 °C, a housingis required, the DC CS ts into pre-fabricated, containerizedbuilding modules (g. 2.2-14). Containerized arrangementsfurther have the advantage to pre-assemble and test wholeswitchyard/substation layouts locally at the manufacturer’s orthe container builder’s plant, cutting short remote erection andcommissioning efforts and costs, as well as simplifying theinterface to civil works. Layouts with identical design which arerepetitively used in a HVDC scheme can be planned and exe-cuted likewise, e.g. cable transition stations. Building andfoundation costs can therefore be greatly reduced.

Fig. 2.2-14: 320 kV containerized arrangement

Fig. 2.2-13: 320 kV DC compact switchgear in the Siemens factoryin Berlin

Finally, an underground installation hidden from view and publicaccess is possible thanks to the encapsulation and compactdesign.

Regarding planned projects in densely populated areas, withcritical points which are already occupied by trafc junctions andAC overhead lines as well as by natural barriers like rivers, hugepotential for compact DC transmission solutions is existent.


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Table 2.2-1: Technical data of ±320 kV DC CS

Technical data for switchgear type ±320 kV DC CS

Rated voltage ±320 kV

Rated current 4,000 ARated short-circuit current 50kA/1sec

Max. continuous operating voltage ±336 kV

Lightning impulse voltage to earth/across terminals

±1175 kV±1175 kV±336 kV

Switching impulse voltage to earth/across terminals

±950 kV±950 kV±336 kV

DC withstand voltage 504 kV, 60 min

Ambient temperature -30°C…+50°C

Application Indoor/Outdoor

Contact person to be quoted in the Power Engineering Guide:Dr. Denis [email protected] / 7-44510Questions regarding this draft:Maik [email protected] / 7-43518

~

Bipolarconguration

AC

U

t

AC + DC DC

U

t

U

t

Converter DCswitchyard

Transition stationcable – OHL

Multi-terminalstation

Fig. 2.2-15: Application for DC compact switchgear, between transformer and valves, DC switchyard, transition station and multi-terminalstation


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2.2. Siemens HVDC Control System: Win-TDCThe control and protection system is an important element in anHVDC transmission. The Siemens control and protection systemfor HVDC has been designed with special focus on high exibilityand high dynamic performance, and benets from the know-ledge gained from over 30 years of operational experience inHVDC and related elds of other industries (g. 2.2-16).

High reliability is achieved with a redundant and robust design.All control and protection components from the human-machineinterface (HMI), control and protection systems down to themeasuring equipment for DC current and voltage quantities havebeen designed to take advantage of the latest software andhardware developments. These control and protection systemsare based on standard products with a product lifecycle of25 years or more.

The name Win-TDC reects the combination of the PC-based HMIsystem SIMATIC WinCC and the high-performance industrialcontrol system SIMATIC TDC for Microsoft Windows.

SIMATIC WinCC (Windows Control Centre) is used for operatorcontrol and monitoring of HVDC systems.

SIMATIC TDC (Technology and Drive Control) is a high-perfor-mance automation system which allows the integration of bothopen-loop and high-speed closed-loop controls within this singlesystem. It is especially suitable for HVDC (and other powerelectronics applications) demanding high-performance closed-loop control. For extremely fast control functions as required inHVDC PLUS systems, SIMATIC TDC is complemented by thededicated PLUSCONTROL comprising the fast Current ControlSystem (CCS) and the Module Management System (MMS).

SIMATIC WinCC and SIMATIC TDC are used in a wide range of in-dustrial applications including power generation and distribution.

In Siemens LCC HVDC systems, the DC currents and voltages aremeasured with a hybrid electro-optical system: DC current with ashunt located at HV potential, DC voltage with a resistive/capacitive voltage divider. Both systems use laser-poweredmeasuring electronics so that only optical connections are madeto the ground level controls – this provides the necessary HVisolation and noise immunity.

For HVDC PLUS, the DC currents are measured with a zero uxmeasuring system, which provides the required accuracy anddynamic response for fast control during grid transients. Thezero ux cores are located at ground level on suitable locations,e. g., converter hall bushings or cable sealing ends.

Siemens provides proven hardware and software systems builtaround state-of-the-art technologies. Their performance andreliability fulls the most demanding requirements for both newinstallations and control system replacement (g. 2.2-17).

PLUSCONTROLSIMATIC TDC

Measuring

Operator Level

C&P Level

I/O Level

I/O Unit I/O Unit

Local HMI

Remote HMI

SCADA Interface

RCI

SIMATIC WinCC

CCS

MMS 1 MMS n

Fig. 2.2-16: Win-TDC hierarchy – More than 30 years of experienceare built into the hie rarchical Siemens HVDC controlsystem which is based on standard components mostwidely used also in other industries

Fig. 2.2-17: The control and protection cubicles are intensively tes tedin the Siemens laboratories before they are shippedto site, assuring fast and smooth commissioning of theHVDC system


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For further information:www.siemens.com/energy/hvdcwww.siemens.com/energy/hvdc-pluswww.energy.siemens.com/hq/en/power-transmission/hvdc/ innovations.htm

2.2. Services

The following set of services completes the Siemens HVDCportfolio.

Turnkey serviceExperienced staff designs, installs and commissions the HVDCsystem on a turnkey basis.

Project nancingSiemens is ready to assist customers in nding proper projectnancing.

General servicesExtended support is provided to customers of Siemens from thevery beginning of HVDC system planning, including:• Feasibility studies• Drafting the specication• Project execution• System operation and long-term maintenance• Consultancy on upgrading/replacement of components/

redesign of older schemes, e. g., retrot of mercury-arc valvesor relay-based controls.

Studies during contract execution are conducted on systemengineering, power system stability and transients:• Load-ow optimization• HVDC systems basic design• System dynamic response• Harmonic analysis and lter design for LCC HVDC• Insulation and protection coordination• Radio and PLC interference• Special studies, if any.


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2.3 Flexible AC TransmissionSystems

Flexible AC Transmission Systems (FACTS) have been evolving toa mature technology with high power ratings. The technology,proven in numerous applications worldwide, became a rst-rate,highly reliable one. FACTS, based on power electronics, havebeen developed to improve the performance of weak AC systemsand to make long distance AC transmission feasible and are anessential part of Smart Grid and Super Grid developments (referto chapter 1).

FACTS can also help solve technical problems in the interconnectedpower systems. FACTS are available in parallel connection:• Static Var Compensator (SVC)• Static Synchronous Compensator (STATCOM)

or in series connection:• Fixed Series Compensation (FSC)• Thyristor Controlled/Protected Series Compensation (TCSC/TPSC).

2.3.1 Parallel Compensation

Parallel compensation is dened as any type of reactive powercompensation employing either switched or controlled units thatare connected in parallel to the transmission system at a powersystem node.

Mechanically Switched Capacitors/Reactors (MSC/MSR)Mechanically switched devices are the most economical reactivepower compensation devices (g. 2.3-1a).• Mechanically switched capacitors are a simple but low-speed

solution for voltage control and network stabilization under

Fig. 2.3-1a: Mechanically switched capacitors (MSC), mechanically switched reactors (MSR) and mechanically switched capacitorswith damping network (MSC DN)

Fig. 2.3-1b: Static var compensator (SVC) with three branches (TCR, TSC, lter) and coupling transformerFig. 2.3-1c: SVC PLUS connected to the transmission systemFig. 2.3-1d: Hybrid SVC connected to the transmission system

a) b) c)

1 1

2

1

2

3

8 92

3 33

3

2

3

5 5

46

72

4

3

3

5

6

7

d)

2

Hybrid SVC

≤ 800 kVIndividual MVAr

MSC (DN)/MSR(DN = Damping network)

SVC

Parallel compensation

1 Switchgear 2 Capacitor 3 Reactor 4 Thyristor valve(s) 5 Transformer 6 IGBT converter 7 DC capacitors 8 Arrester 9 Resistor

≤ 800 kV≤ 300 MVAr

≤ 800 kV≤ 1000 MVAr

≤ 800 kV≤ ± 250 MVAr

(and more)

SVC PLUS

MSC MSR

MSC DN

heavy load conditions. Their utilization has almost no effect onthe short-circuit power but it increases the voltage at the pointof connection

• Mechanically switched reactors have exactly the oppositeeffect and are therefore preferable for achieving stabilizationunder low load conditions

• An advanced form of mechanically switched capacitor is theMSCDN. This device is an MSC with an additional dampingcircuit for avoidance of system resonances.

Static Var Compensator (SVC)Static var compensators are a fast and reliable means of control-ling voltage on transmission lines and system nodes (g. 2.3-1b,

Fig. 2.3-2: Static Var Compensator (SVC) installation


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2.3 Flexible AC Transmission Systems


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g. 2.3-2). The reactive power is changed by switching or con-trolling reactive power elements connected to the secondaryside of the transformer. Each capacitor bank is switched ON andOFF by thyristor valves (TSC). Reactors can be either switched(TSR) or controlled (TCR) by thyristor valves.

When system voltage is low, the SVC supplies capacitive reactivepower and rises the network voltage. When system voltage ishigh, the SVC generates inductive reactive power and reducesthe system voltage.

Static var compensators perform the following tasks:• Improvement in voltage quality• Dynamic reactive power control• Increase in system stability• Damping of power oscillations• Increase in power transfer capability• Unbalance control (option).

The design and conguration of an SVC, including the size of theinstallation, operating conditions and losses, depend on thesystem conditions (weak or strong), the system conguration(meshed or radial) and the tasks to be performed.

SVC PLUS – new generation of STATCOMSVC PLUS is an advanced STATCOM which uses Voltage-SourcedConverter (VSC) technology based on Modular MultilevelConverter (MMC) design.• MMC provides a nearly ideal sinus-shaped waveform on the AC

side. Therefore, there is only little – if any – need for harmonicltering

• MMC allows for low switching frequencies, which reducessystem losses.

• SVC PLUS uses robust, proven standard components, such astypical AC power transformers, reactors and switchgear.

• Using containerized SVC PLUS solutions with small operatingranges will result in signicant space savings in comparison toa conventional SVC installation.

ApplicationsSVC PLUS with its superior undervoltage performance fullls thesame task as conventional SVCs. Due to the advanced tech-nology, SVC PLUS is the preferred solution for grid access solu-tions (e. g., wind parks).

Modular system designThe modular SVC PLUS is equipped with industrial class IGBT(Insulated Gate Bipolar Transistors) power modules and DCcapacitors.• A very high level of system availability, thanks to the

redundancy of power modules• Standard WinCC and SIMATIC TDC control and protection

hardware and software are fully proven in practice in a widerange of applications worldwide.

Portfolio• Standardized congurations are available: ± 25, ± 35, and

± 50 MVAr as containerized solutions. Up to four of these unitscan be congured as a fully parallel operating system

• Easily expendable and relocatable• Open rack modular system conguration (in a building) allows

for operating ranges of ± 250 MVAr and more.• Hybrid SVCs comprise a combination of both, multilevel

STATCOM and conventional thyristor based SVC technology.This solution combines the benets of the SVC PLUS, especiallythe undervoltage performance, with the exibility ofunsymmetrical operating ranges by TSR and TSC.

Fig. 2.3-3: Two SVC PLUS units in New Zealand

Fig. 2.3-4: SVC PLUS containerized solution


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2.3 Flexible AC Transmission Systems


Fig. 2.3-5: View of a TCSC system

2.3.2 Series Compensation

Series compensation is dened as inser tion of

power engineering guide edition 7 1

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