Siemens Power Engineering Guide

Your local representative:

Distributed by:

Siemens Aktiengesellschaft

Power Transmission and Distribution Group International Business Development, Dept. EV IBD

P.O. Box 3220 D-91050 Erlangen

Phone: ++ 49 - 9131-73 45 40 Fax: ++ 49-9131-73 45 42 Power Transmission and Distribution group online:

http://www.ev.siemens.de

Power Engineering Guide

Transmission and Distribution

Sales locations worldwide (EV):

Siemens Power Transmission and Distribution Group offers intelligent so-lutions for the transmission and distri-bution of power from generating plants to customers. The Group is a product supplier, systems integrator and service provider, and specializes

in the following systems and services:

■High-voltage systems

■Medium-voltage systems

■Metering

■Secondary systems

■Power systems control and energy management

■Power transformers

■Distribution transformers

■System planning

■Decentralized power supply systems. Siemens’ service includes the setting up of complete turnkey installations, offers advice, planning, operation and training and provides expertise and commitment as the complexity of this task requires.

Backed by the experience of worldwide projects, Siemens can always offer its customers the optimum cost-effective concept individually tailored to their needs.

We are there – wherever and when-ever you need us – to help you build plants better, cheaper and faster.

Dr. Hans-Jürgen Schloß Vice President

Siemens Aktiengesellschaft Power Transmission and Distribution

Siemens AG is one of the world’s

leading international electrical and electronics companies.

With 416 000 employees in more than 190 countries worldwide, the company is divided into various Groups.

One of them is Power Transmission and Distribution.

The Power Transmission and

Distribution Group of Siemens with

24 700 employees around the world plans, develops, designs, manufactures and markets products, systems and complete turn-key electrical infrastruc-ture installations.

The group owns a growing number of engineering and manufacturing facilities in more than 100 countries throughout the world. All plants are, or are in the process of being certified to ISO 9000/9001 practices. This is of significant benefit for our customers. Our local manufacturing capability makes us strong in global sourcing, since we manufacture products to IEC as well as ANSI/NEMA standards in plants at various locations around the world.

Siemens Power Transmission and Distribution Group (EV) is capable of providing everything you would expect from an electrical engineering company with a global reach.

The Power Transmission and Distribu-tion Group is prepared and competent, to perform all tasks and activities in-volving transmission and distribution of electrical energy.

This Power Engineering Guide is de-vised as an aid to electrical engineers who are engaged in the planning and specifying of electrical power genera-tion, transmission, distribugenera-tion, control, and utilization systems. Care has been taken to include the most important application, performance, physical and shipping data of the equipment listed in the guide which is needed to perform preliminary layout and engineering tasks for industrial and utility-type installations.

The equipment listed in this guide is designed, rated, manufactured and tested in accordance with the Interna-tional Electrotechnical Commission (IEC) recommendations.

However, a number of standardized equipment items in this guide are de-signed to take other national standards into account besides the above codes, and can be rated and tested to ANSI/ NEMA, BS, CSA, etc. On top of that, we manufacture a comprehensive range of transmission and distribution equipment specifically to ANSI/NEMA codes and regulations.

Two thirds of our product range is less than five years old. For our cus-tomers this means energy efficiency, environmental compatibility, reliability and reduced life cycle cost.

For details, please see the individual product listings or inquire.

Whenever you need additional infor-mation to select suitable products from this guide, or when questions about their application arise, simply call your local Siemens office.

Sales locations worldwide:

http://www.ev.siemens.de/en/pages/ salesloc.htm

Quality and Environmental Policy

Quality and Environmental – Our first priority

Transmission and distribution equipment from Siemens means worldwide activities in engineering, design, development, man-ufacturing and service.

The Power Transmission and Distribution Group of Siemens AG, with all of its divi-sions and relevant locations, has been awarded and maintains certification to DIN EN ISO 9001 and DIN EN ISO 14001.

Certified quality

Siemens Quality Management and Environ-mental Management System gives our customers confidence in the quality of Siemens products and services. Certified to be in compliance with DIN EN ISO 9001 and DIN EN ISO 1400, it is the registered proof of our reliabilty.

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Power Transmission Systems

High Voltage

Medium Voltage

Low Voltage

Transformers

Protection and Substation Control

Power Systems Control and Energy Management

Metering

Services

System Planning

Conversion Factors and Tables

Contacts and Internet Addresses

Conditions of Sales and Delivery

Energy management systems are also im-portant, to ensure safe and reliable opera-tion of the transmission network.

Distribution

In order to feed local medium-voltage dis-tribution systems of urban, industrial or ru-ral distribution areas, HV/MV main substa-tions are connected to the subtransmission systems. Main substations have to be lo-cated next to the MV load center for rea-sons of economy. Thus, the subtransmis-sion systems of voltage levels up to 145 kV have to penetrate even further into the populated load centers.

The far-reaching power distribution system in the load center areas is tailored exclusive-ly to the needs of users with large numbers of appliances, lamps, motor drives, heating, chemical processes, etc. Most of these are connected to the low-voltage level. The structure of the low-voltage distribu-tion system is determined by load and re-liability requirements of the consumers, as well as by nature and dimensions of the area to be served. Different consumer char-acteristics in public, industrial and commer-cial supply will need different LV network configurations and adequate switchgear and transformer layout. Especially for indus-trial supply systems with their high number of motors and high costs for supply inter-ruptions, LV switchgear design is of great importance for flexible and reliable opera-tion.

Independent from individual supply charac-teristics in order to avoid uneconomical high losses, however, the substations with the MV/LV transformers should be located as close as possible to the LV load centers. The compact load center substations should be installed right in the industrial produc-tion area near to the LV consumers. The superposed medium-voltage system has to be configured to the needs of these substations and the available sources (main substation, generation) and leads again to different solutions for urban or rural public supply, industry and large building centers. In addition distribution management sys-tems can be tailored to the needs, from small to large systems and for specific re-quirements.

Fig. 2: Distribution: Principle configuration of distribution systems Consumers

MV/LV transformer

level

Low-voltage supply system

Large buildings with distributed transformers vertical LV risers and internal installation per floor

Industrial supply with distributed transformers with subdistribution board and motor control center Public supply

with pillars and house connections internal installation

Local medium-voltage distribution system

Ring type

Connection of

large consumer Industrial supplyand large buildings Public supply

Spot system Feeder cable

Medium voltage substations

MV/LV substation looped in MV cable by load-break switch-gear in different combinations for individual substation design, transformers up to 1000 kVA LV fuses Circuit-breaker Load-break switch Consumer-connection substation looped in or connected to feeder cable with circuit-breaker and load-break switches for connec-tion of spot system in different layout

Main substation with transformers up to 63 MVA

HV switchgear MV switchgear

Fig. 3: System Automation:

Principle configuration of protection, control and communication systems

Power system switchgear

SCADA functions Distribution management functions Network analysis Power and scheduling applications Grafical information systems Training simulator

System coordination level

Control room equipment

Bay protection – Overcurrent – Distance – Differential etc. Bay switching interlocking Control Bay coordination level

Other bays

BB and BF (busbar and breaker failure)

protection Substation control Data processing Switchgear

interlocking

Data and signal input/output

Automation Other bays

Substation coordination level

Power system substation

Power network telecommunication systems

Other sub-stations Other sub-stations

Power line carrier communication

Fiber-optic communication

Metering Despite the individual layout of networks,

common philosophy should be an utmost simple and clear network design to obtain

■flexible system operation

■clear protection coordination

■short fault clearing time and

■efficient system automation.

The wide range of power requirements for individual consumers from a few kW to some MW, together with the high number of similar network elements, are the main characteristics of the distribution system and the reason for the comparatively high specific costs. Therefore, utmost standard-ization of equipment and use of mainte-nance-free components are of decisive im-portance for economical system layout. Siemens components and systems cater to these requirements based on worldwide experience in transmission and distribution networks.

Protection, operation, control and metering

Safe, reliable and economical energy supply is also a matter of fast, efficient and reliable system protection, data transmission and processing for system operation. The com-ponents required for protection and opera-tion benefit from the rapid development of information and communication technology. Modern digital relays provide extensive possibilities for selective relay setting and protection coordination for fast fault clear-ing and minimized interruption times. Re-mote Terminal Units (RTUs) or Substation Automation Systems (SAS) provide the data for the centralized monitoring and control of the power plants and substations by the energy management system.

Siemens energy management systems ensure a high supply quality, minimize gen-eration and transmission costs and opti-mally manage the energy transactions. Modularity and open architecture offer the flexibility needed to cope with changed or new requirements originating e.g. from de-regulation or changes in the supply area size. The broad range of applications in-cludes generation control and scheduling, management of transmission and distribu-tion networks, as well as energy trading. Metering devices and systems are impor-tant tools for efficiency and economy to survive in the deregulated market. For ex-ample, Demand Side Management (DSM) allows an electricity supply utility from a control center to remotely control certain consumers on the supply network for load control purposes. Energy meters are used for measuring the consumption of electricity, gas, heat and water for purposes of billing in the fields of households, commerce, industry and grid metering.

Overall solutions – System planning

Of crucial importance for the quality of power transmission and distribution is the integration of diverse components to form overall solutions.

Especially in countries where the increase in power consumption is well above the average besides the installation of gener-ating capacity, construction and extension of transmission and distribution systems must be developed simultaneously and together with equipment for protection, supervision, control and metering. Also, for the existing systems, changing load struc-tures, changing requirements due to energy market deregulation and liberalization and/ or environmental regulations, together with the need for replacement of aged equip-ment will require new installations. Integral power network solutions are far more than just a combination of products and components. Peculiarities in urban de-velopment, protection of the countryside and of the environment, and the suitability for expansion and harmonious integration in existing networks are just a few of the factors which future-oriented power sys-tem planning must take into account.

Outlook

The electrical energy supply (generation, transmission and distribution) is like a pyra-mid based on the number of components and their widespread use. This pyramid rests on a foundation formed by local expan-sion of the distribution networks and pow-er demand in the ovpow-erall system, which is determined solely by the consumers and their use of light, power and heat. These basic applications arise in many variations and different intensities throughout the en-tire private, commercial and industrial sec-tor (Fig. 4).

Reliability, safety and quality (i.e. voltage and frequency stability) of the energy sup-ply are therefore absolute essentials and must be assured by the distribution net-works and transmission systems.

Consumers

Light Power Heat

Monitoring, Control, Automation Applications

Generation Transmission

Distribution

Fig. 4: Industrial applications

is a crucial factor in the economic and so-cial development of a particular country. In the industrialized countries the concept of the “decentralized power supply” is also gaining ground, largely because of environ-mental concern. This has had its conse-quences for the generation of electricity: wind power is experiencing a renaissance, more development work is being carried out into photovoltaic devices and combined heat and power cogeneration plants are growing in popularity in many areas for both ecological and economic reasons. These developments are resulting in some entirely new energy network structures.

Additional tasks...

The scope and purpose of tomorrow’s dis-tribution systems will no longer be to sim-ply “supsim-ply electricity”. In future they will be required to “harvest” power and redis-tribute it more economically and take into account, among other considerations, envi-ronmental needs. In the past it was no easy task to supply precisely the right amount of electricity according to demand because, as is well-known, electricity cannot be readily stored and the loads were continually chang-ing. Demand scheduling was very much based on statistical forecasting – not an ex-act science and one that cannot by its very nature take into account realtime variations. Demand scheduling problems can become particularly acute when power stations of limited generating capacity are on line.

The changing state of the world’s ener-gy markets and the need to conserve re-sources is promoting more intelligent solutions to the distribution of man’s silent servant, electricity. Change is gen-erally wrought by necessity, often driven by a variety of factors, not least social, political, economic, environmental and technological considerations. Currently the world’s energy supply industries – principally gas and electricity – are in the process of undergoing radical and crucial change that is driven by a mix-ture of all these considerations. The col-lective name given to the factors affect-ing the electricity supply industry worldwide is deregulation.

This is the changing operating scenario the electricity supply industry as a whole faces as it moves inexorably into the 21st century. How can it rise to the challenge of liberal-ized markets and the opportunities presented by deregulation? One of the answers is the better use of information technology and “intelligent” control to affect the necessary changes born of deregulation. However, to achieve this utilities need to be very sure of the technical and commercial compe-tence of their systems suppliers. Failure could prove to be very costly not just in fi-nancial terms, but also for a utility’s reputa-tion with its consumers in what is becom-ing increasbecom-ingly a buyer’s market. Formbecom-ing and maintaining close partnerships with long-established systems suppliers such as Siemens is the best way of ensuring suc-cess with deregulation into the millennium. Siemens can look back on over 100 years of working in close co-operation with power utilities throughout the world. This accumu-lated experience allows the company’s Power Transmission and Distribution Group to address not just technical issues, but also better appreciate many of the opera-tional and commercial aspects of electricity distribution. Experience gained over the past decade with the many-and-varied aspects of deregulation puts the Group in an almost unique position to advise utilities as to the best solutions for taking full advantage of the opportunities offered by deregulation.

Innovation the issue of change

Although today’s technology obviously plays a very important role in the company’s current business, innovation has always been at the vanguard of its activities; indeed it is the common thread that has run through the company since its incep-tion 150 years ago. In future power dis-tribution technology, computer software, power electronics and superconductivity will play increasingly prominent roles in in-novative solutions. Scope for new

technol-ogies is to be found in decentralized energy supply concepts and in meeting the needs of urban conurbations. Siemens is no longer just a manufacturer of systems and equip-ment, it is now much more. Overall con-cepts are becoming ever more important.

All change!

Power distribution technology has not changed significantly over the past forty years… indeed, the “rules of the game” have remained the same for a much longer period of time.

A new challenge

Recently decentralized power supply sys-tems have cornered a growing share of the market for a number of reasons. In devel-oping and industrializing countries, it has become clear that the energy policies and systems solutions adopted by nations with well-established energy infrastructures are not always appropriate. Frequently it is more prudent to start with small decentral-ized power networks and to expand later in a progressive way as demand and eco-nomics permit. Much benefit can also be gained if generation makes use of natural or indigenous resources such as the sun, water, wind or biomass. Countries that struggle with population growth and migra-tion to the towns and cities clearly need to pay close attention to protecting their bal-ance of payments. In such cases, the expan-sion of power supplies into the countryside

Nowadays these and similar problems are not insoluble because of decentralized power supplies and the use of “intelligent” control. The Power Transmission and Dis-tribution Group has developed concepts for the economic resolution of peak energy de-mand. One is to use energy stores. Batteries are an obvious choice, for these can be equipped with power electronics to en-hance energy quality as well as storing electricity.

Intelligent energy management…

One of the options for matching the amount of electricity available to the amount being demanded is, even today, the rarely used technique of load control. Energy saving can mean much more than just consuming as few kilowatt-hours as possible. It can also mean achieving the flexibility of demand that can make a valuable contribution to a country’s economy. Naturally, in places such as hospitals, textile factories and electronic chip fabrication plants it is extremely impor-tant for the power supply not to fail – not even for a second. In other areas of elec-tricity consumption, however, there is much more room for manoeuvre. Controlled in-terruptions of a few minutes, and even a few hours, can often be tolerated without causing very much difficulty to those in-volved. There are other applications where the time constant or resilience is high, e.g. cold stores and air-conditioning plants, where energy can be stored for periods of up to several hours. Through the application of “intelligent” control and with suitable finan-cial encouragement (usually in the form of flexible tariff rates) there is no doubt that very much more could be made of load control.

Improving energy quality…

Power electronics systems, for example SIPCON, can help improve energy quality – an increasingly important factor in deregu-lated energy markets. Energy has now be-come a product. It has its price and a de-fined quality. Consumers want a definite quality of energy, but they also produce reaction effects on the system that are detrimental to quality (e.g. harmonics or reactive power).

Energy quality first has to be measured and documented, for example with the SIMEAS®

family of quality recorders. These measure-ments are important for price setting, and can serve as the basis for remedial action, such as with active or passive filters. Power electronics development has opened up many new possibilities here, although con-siderable progress may still be made in this area – a breakthrough in silicon carbide technology, for example.

Alternatives…

It should be appreciated, however, that de-centralized power supplies are not a pana-cea. For those places where energy density requirements are high, large power stations are still the answer, and especially when they can supply district heating. Theoreti-cally, it should still be possible to employ conventional technology to transport very large amounts of electricity to the megaci-ties of the 21st Century. Even if the use of overhead power lines was not an option, due to say there being insufficient space or

resistance from people living nearby, it would be possible to use gas-insulated lines (GIL), an economical alternative investigated by Siemens.

The development aim of reducing costs has meanwhile been attained here, and cost-effective applications involving distances of serveral kilometres are therefore possible. The system costs for the gas-insulated trans-mission lines (GIL) developed by Siemens exceed those of overhead lines only by about a factor of 10.

Fig. 6: Silicon carbide

Fig. 7: GIL

Cooling station (liquid nitrogen) GIL

Energy store

Switching station Power plants

Energy management via satellite

Long-distance DC transmission

Converter station Solar energy

Wind energy

Distribution station

Biomass power plant Irrigation system

Fuel cells

Pumping station

Fig. 8: The mega-cities of the 21st century and the open countryside will need different solutions – very high values of connection density in the former and decentralised configurations in the latter

This has been achieved by laying the tubu-lar conductor using methods simitubu-lar to those employed with pipelines. Savings were also made by simplifying and standardizing the individual components and by using a gas mixture consisting of sulfur hexafluo-ride (SF6) and nitrogen (N2).

The advantages of this new technology are low resistive and capacitive losses. The electric field outside of the enclosure is zero, and the magnetic field is negligibly small. No cooling and no phase angle compensa-tion are required. GILs are not a fire hazard and are simple to repair.

Energy trade

The new “rules of the game” that are being introduced in power supply business eve-rywhere are demanding more capability from utility IT systems, especially in areas such as energy trading. Siemens has been in the fortunate position of being able to accumulate early practical experience in this field in markets where deregulation is being introduced very quickly – such as the United Kingdom, Scandinavia and the USA – and so is now able to offer sophisticated systems and expertise with which utilities can get to grips with the demands of the new commercial environment.

In the past it was always security of supply that took the highest priority for a utility. Now, however, although it remains an im-portant subject, more and more

sharehold-ers are demanding a more reasonable re-turn on their investment. Deregulation gen-erally means privatization; profit orientation is therefore clearly going to take over from concern with cost. In addition this means that competition will inevitably produce some concessions in the price of electrici-ty, which will increase the pressure on en-ergy suppliers. Many power supply compa-nies are striving to introduce additional energy services, thereby making the pure price of energy not the only yardstick their customers apply when deciding how to make their purchases.

Siemens – the energy systems house

Siemens is offering solutions to the prob-lems that are governed by the new “rules of the game”. The company possesses con-siderable expertise, mainly because it is a global player, but also because it covers the total spectrum of products necessary for the efficient transmission and distribution of electricity. As with other Groups within the company, Power Transmission and Distribu-tion no longer regards itself as simply a pur-veyor of hardware. In future Siemens will be more of a provider of services and total solutions. This will mean embracing many new disciplines and skills, not least finan-cial control and complete project manage-ment. One of the reasons is that in future “BOT” (Build, Operate & Transfer)

compa-nies and independent operating utilities will no longer confine their activities to just en-ergy production; they will be expected to become increasingly involved in energy dis-tribution too.

Potential for the future

The ongoing development of high-temper-ature superconductors will doubtless ena-ble much to be achieved. Major operational innovations will, nonetheless, come from the more pervasive use of communications and data systems – two areas of technolo-gy where innovations can be seen every 18 months. Consequently, it will be from these areas that the enabling impetus for significant advances in power engineering will come.

Contents

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Transmission Lines (GIL) ... 2/38 Overhead Power Lines ... 2/40 High-Voltage Direct Current Transmission ... 2/49 Power Compensation in Transmission Systems ... 2/52

High Voltage

High Voltage

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Introduction

High-voltage substations form an important link in the power transmission chain be-tween generation source and consumer. Two basic designs are possible:

Air-insulated outdoor switchgear of open design (AIS)

AIS are favorably priced high-voltage sub-stations for rated voltages up to 800 kV which are popular wherever space restric-tions and environmental circumstances do not have to be considered. The individual electrical and mechanical components of an AIS installation are assembled on site. Air-insulated outdoor substations of open design are not completely safe to touch and are directly exposed to the effects of weather and the environment (Fig. 1).

Gas-insulated indoor or outdoor switchgear (GIS)

GIS compact dimensions and design make it possible to install substations up to 550 kV right in the middle of load centers of urban or industrial areas. Each circuit-breaker bay is factory assembled and includes the full complement of isolator switches, grounding switches (regular or make-proof), instrument transformers, control and protection equipment, inter-locking and monitoring facilities commonly used for this type of installation. The earthed metal enclosures of GIS assure not only insensitivity to contamination but also safety from electric shock (Fig. 2).

Gas-insulated transmission lines (GIL)

A special application of gas-insulated equipment are gas-insulated transmission lines (GIL). They are used where high-volt-age overhead lines are not suitable for any reason. GIL have a high power transmis-sion capability, even when laid under-ground, low resistive and capacitive losses and low electromagnetic fields.

Fig. 1: Outdoor switchgear

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High-Voltage Switchgear for Substations

Turnkey Installations

High-voltage switchgear is normally com-bined with transformers and other equip-ment to complete transformer substations in order to

■Step-up from generator voltage level to high-voltage system (MV/HV)

■Transform voltage levels within the high-voltage grid system(HV/HV)

■Step-down to medium-voltage level of distribution system (HV/MV) The High Voltage Division plans and con-structs individual high-voltage switchgear installations or complete transformer sub-stations, comprising high-voltage switch-gear, medium-voltage switchswitch-gear, major components such as transformers, and all ancillary equipment such as auxiliaries, control systems, protective equipment, etc., on a turnkey basis or even as general contractor.

The spectrum of installations supplied ranges from basic substations with single busbar to regional transformer substations with multiple busbars or 1 1_/

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circuit-break-er arrangement for rated voltages up to 800 kV, rated currents up to 8000 A and short-circuit currents up to 100 kA, all over the world.

The services offered range from system planning to commissioning and after-sales service, including training of customer per-sonnel.

The process of handling such an installa-tion starts with preparainstalla-tion of a quotainstalla-tion, and proceeds through clarification of the order, design, manufacture, supply and cost-accounting until the project is finally billed. Processing such an order hinges on methodical data processing that in turn contributes to systematic project handling. All these high-voltage installations have in common their high-standard of engi-neering, which covers power systems, steel structures, civil engineering, fire pre-cautions, environmental protection and control systems (Fig. 3).

Every aspect of technology and each work stage is handled by experienced engineers. With the aid of high-performance computer programs, e.g. the finite element meth-od (FEM), installations can be reliably de-signed even for extreme stresses, such as those encountered in earthquake zones. All planning documentation is produced on modern CAD systems; data exchange with other CAD systems is possible via stand-ardized interfaces.

By virtue of their active involvement in national and international associations and standardization bodies, our engineers are

always fully informed of the state of the art, even before a new standard or specifi-cation is published.

Quality/Environmental Management

Our own high-performance, internationally accredited test laboratories and a certified QM system testify to the quality of our products and services.

Milestones:

■1983: Introduction of a quality system on the basis of Canadian standard CSA Z 299 Level 1

■1989: Certification of the SWH quality system in accordance with

DIN EN ISO 9001 by the German Association for Certification of Quality Systems (DQS)

■1992: Repetition audit and extension of the quality system to the complete EV H Division

■1992: Accreditation of the test labora-tories in accordance with DIN EN 45001 by the German Accreditation Body for Technology (DATech)

■1994: Certification of the environmental-systems in accordance with

DIN EN ISO 14001 by the DQS

■1995: Mutual QEM Certificate

Ancillary equipment Design Civil Engineering Buildings, roads, foundations Structural Steelwork Gantries and substructures Major com-ponents, e.g. trans-former Substation Control Control and monitoring, measurement, protection, etc. AC/DC auxililiaries Surge diverte rs Earth ing syste m Po we r c able s

Control and signal cables Carrier -frequ. equipment Ve_n tila tio n Lig htn in_g Environmental protection Fire protection

Fig. 3: Engineering of high-voltage switchgear

Know how, experience and worldwide presence

A worldwide network of liaison and sales offices, along with the specialist depart-ments in Germany, support and advise our customers in all matters of switchgear technology.

Siemens has for many years been a lead-ing supplier of high-voltage equipment, regardless of whether AIS, GIS or GIL has been concerned. For example, outdoor substations of longitudinal in-line design are still known in many countries under the Siemens registered tradename “Kiel-linie”. Back in 1968, Siemens supplied the world’s first GIS substation using SF6 as

insulating and quenching medium. Gas-in-sulated transmission lines have featured in the range of products since 1976.

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Standards

Air-insulated outdoor substations of open design must not be touched. Therefore, air-insulated switchgear (AIS) is always set up in the form of a fenced-in electrical op-erating area, to which only authorized per-sons have access.

Relevant IEC 60 060 specifications apply to outdoor switchgear equipment. Insulation coordination, including minimum phase-to-phase and phase-to-ground clearances, is effected in accordance with IEC 60071. Outdoor switchgear is directly exposed to the effects of the environment such as the weather. Therefore it has to be designed based on not only electrical but also envi-ronmental specifications.

Currently there is no international standard covering the setup of air-insulated outdoor substations of open design. Siemens de-signs AIS in accordance with DIN/VDE standards, in line with national standards or customer specifications.

The German standard DIN VDE 0101 (erec-tion of power installa(erec-tions with rated volt-ages above 1 kV) demonstrates typically the protective measures and stresses that have to be taken into consideration for air-insulated switchgear.

Protective measures

Protective measures against direct contact, i. e. protection in the form of covering, obstruction or clearance and appropriately positioned protective devices and mini-mum heights.

Protective measures against indirect touch-ing by means of relevant groundtouch-ing meas-ures in accordance with DIN VDE 0141. Protective measures during work on equipment, i.e. during installation must be planned such that the specifications of DIN EN 50 110 (VDE 0105) (e.g. 5 safety rules) are complied with

■Protective measures during operation, e.g. use of switchgear interlock equip-ment

■Protective measures against voltage surges and lightning strike

■Protective measures against fire, water and, if applicable, noise insulation.

Stresses

■Electrical stresses, e.g. rated current, short-circuit current, adequate creepage distances and clearances

■Mechanical stresses (normal stressing), e.g. weight, static and dynamic loads, ice, wind

■Mechanical stresses (exceptional stresses), e.g. weight and constant loads in simultaneous combination with maximum switching forces or short-circuit forces, etc.

■Special stresses, e.g. caused by instal-lation altitudes of more than 1000 m above sea level, or earthquakes

Variables affecting switchgear

installation

Switchgear design is significantly influ-enced by:

■Minimum clearances (depending on rated voltages) between various active parts and between active parts and earth

■Arrangement of conductors

■Rated and short-circuit currents

■Clarity for operating staff

■Availability during maintenance work, redundancy

■Availability of land and topography

■Type and arrangement of the busbar disconnectors

The design of a substation determines its accessibility, availability and clarity. The design must therefore be coordinated in close cooperation with the customer. The following basic principles apply:

Accessibility and availability increase with the number of busbars. At the same time, however, clarity decreases. Installations involving single busbars require minimum investment, but they offer only limited flex-ibility for operation management and main-tenance. Designs involving 1 1_/

2 and 2

cir-cuit-breaker arrangements assure a high redundancy, but they also entail the high-est costs. Systems with auxiliary or bypass busbars have proved to be economical. The circuit-breaker of the coupling feeder for the auxiliary bus allows uninterrupted replacement of each feeder circuit-breaker. For busbars and feeder lines, mostly wire conductors and aluminum are used. Multi-ple conductors are required where currents are high. Owing to the additional short-circuit forces between the subconductors (pinch effect), however, multiple conduc-tors cause higher mechanical stressing at the tension points. When wire conductors, particularly multiple conductors, are used higher short-circuit currents cause a rise not only in the aforementioned pinch ef-fect but in further force maxima in the event of swinging and dropping of the con-ductor bundle (cable pull). This in turn re-sults in higher mechanical stresses on the switchgear components. These effects can be calculated in an FEM (Finite Element Method) simulation (Fig. 4).

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When rated and short-circuit currents are high, aluminum tubes are increasingly used to replace wire conductors for busbars and feeder lines. They can handle rated currents up to 8000 A and short-circuit currents up to 80 kA without difficulty. Not only the availability of land, but also the lie of the land, the accessibility and lo-cation of incoming and outgoing overhead lines together with the number of trans-formers and voltage levels considerably influence the switchgear design as well. A one or two-line arrangement, and possi-bly a U arrangement, may be the proper solution. Each outdoor switchgear installa-tion, especially for step-up substations in connection with power stations and large transformer substations in the extra-high-voltage transmission system, is therefore unique, depending on the local conditions. HV/MV transformer substations of the dis-tribution system, with repeatedly used equipment and a scheme of one incoming and one outgoing line as well as two trans-formers together with medium-voltage switchgear and auxiliary equipment, are more subject to a standardized design from the individual power supply compa-nies.

Design of Air-Insulated Outdoor Substations

Fig. 4: FEM calculation of deflection of wire conductors in the event of short circuit

Horizontal displacement in m Vertical displacement in m –1.4 –1.0 –0.6 –0.2 0.2 0.6 1.0 1.4 –1.4 –1.2 –1.0 –0.8 –0.6 –1.6 –1.8 –2.0 –2.2 0

Preferred designs

The multitude of conceivable designs in-clude certain preferred versions, which are dependent on the type and arrangement of the busbar disconnectors:

H arrangement

The H arrangement (Fig. 5) is preferrably used in applications for feeding industrial consumers. Two overhead lines are con-nected with two transformers and inter-linked by a single-bus coupler. Thus each feeder of the switchgear can be main-tained without disturbance of the other feeders. This arrangement assures a high availability.

Special layouts for single busbars up to 145 kV with withdrawable circuit-break-er and modular switchbay arrangement

Further to the H arrangement that is built in many variants, there are also designs with withdrawable circuit-breakers and modular switchbays for this voltage range. For detailed information see the following pages:

Fig. 5: Module plan view

= T1 M M M M M M – F1 – Q0 – T1 – T1 – T5 – Q1 – Q0 – Q8 – T1 – T5 – Q1 – Q0 – Q8 – Q1 – Q1 = T1 – F1 – Q0 – T1 – Q10 – Q11

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For 123/145 kV substations with single busbar system a suitable alternative is the withdrawable circuit-breaker. In this kind of switchgear busbar- and outgoing discon-nector become inapplicable (switchgear

Fig. 6a: H arrangement with withdrawable circuit-breaker, plan view and sections

Fig. 6b: H arrangement with withdrawable circuit-breaker, ISO view Fig. 7: Technical data

without disconnectors). The isolating dis-tance is reached with the moving of the circuit-breaker along the rails, similar to the well-known withdrawable-unit design tech-nique of medium-voltage switchgear. In disconnected position busbar, circuit-break-er and outgoing circuit are separated from each other by a good visible isolating

dis-tance. An electromechanical motive unit ensures the uninterrupted constant moving motion to both end positions. The circuit-breaker can only be operated if one of the end positions has been reached. Move-ment with switched-on circuit-breaker is impossible. Incorrect movement, which would be equivalent to operating a discon-nector under load, is interlocked. In the event of possible malfunction of the posi-tion switch, or of interrupposi-tions to travel between disconnected position and operat-ing position, the operation of the circuit-breaker is stopped.

The space required for the switchgear is reduced considerably. Due to the arrange-ment of the instruarrange-ment transformers on the common steel frame a reduction in the required space up to about 45% in compar-ison to the conventional switchgear sec-tion is achieved.

Description

A common steel frame forms the base for all components necessary for reliable oper-ation. The withdrawable circuit-breaker contains:

■Circuit-breaker type 3AP1F

■Electromechanical motive unit

■Measuring transformer for protection and measuring purposes

■Local control cubicle

All systems are preassembled as far as possible. Therefore the withdrawable CB can be installed quite easily and efficiently on site.

The advantages at a glance

■Complete system and therefore lower costs for coordination and adaptation.

■A reduction in required space by about 45% compared with conventional switchbays

■Clear wiring and cabling arrangement

■Clear circuit state

■Use as an indoor switchbay is also pos-sible. Technical data 123 kV (145 kV) 1250 A (2000 A) 31.5 kA, 1s, (40 kA, 3s) 230/400 V AC 220 V DC Nominal voltage [kV] Nominal current [A] Nominal short [kA] time current

Auxiliary supply/ motive unit [V] Control voltage [V]

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The advantages at a glance

■Complete system and therefore lower costs for coordination and adaptation.

■Thanks to the integrated control cubicle, upgrading of the control room is scarecely necessary.

■A modular switchbay can be inserted very quickly in case of total breakdown or for temporary use during reconstruc-tion.

■A reduction in required space by about 50% compared with conventional switchbays is achieved by virtue of the compact and tested design of the mod-ule (Fig. 8).

■The application as an indoor switchbay is possible.

Design of Air-Insulated Outdoor Substations

Fig. 9: Technical data

Modular switchbay General

As an alternative to conventional substa-tions an air-insulated modular switchbay can often be used for common layouts. In this case the functions of several HV devices are combined with each other. This makes it possible to offer a standard-ized module.

Appropriate conventional air-insulated switchbays consist of separately mounted HV devices (for example circuit-breaker, disconnector, earthing switches, transform-ers), which are connected to each other by conductors/tubes. Every device needs its own foundations, steel structures, earthing connections, primary and secondary termi-nals (secondary cable routes etc.).

Description

A common steel frame forms the base for all components necessary for a reliable op-eration. The modul contains:

■Circuit-breaker type 3AP1F

■Motor-operated disconnecting device

■Current transformer for protection and measuring purposes

■Local control cubicle

All systems are preassembled as far as possible. Therefore the module can be in-stalled quite easily and efficiently on site.

Technical data 123 kV (145 kV) 1250 A (2000 A) 31.5 kA, 1s, (40 kA, 3s) 230/400 V AC 220 V DC Nominal voltage Nominal current Nominal short current Auxiliary supply Control voltage

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Fig. 12: Busbar area with pantograph disconnector of diagonal design, rated voltage 420 kV Fig.11: Central tower design

In-line longitudinal layout, with rotary disconnectors, preferable up to 170 kV The busbar disconnectors are lined up one behind the other and parallel to the longitu-dinal axis of the busbar. It is preferable to have either wire-type or tubular busbars located at the top of the feeder conductors. Where tubular busbars are used, gantries are required for the outgoing overhead lines only. The system design requires only two conductor levels and is therefore clear. If, in the case of duplicate busbars, the second busbar is arranged in U form rela-tive to the first busbar, it is possible to ar-range feeders going out on both sides of the busbar without a third conductor level (Fig. 10).

Fig. 10: Substation with rotary disconnector, in-line design

18000 9000 3000 Dimensions in mm 12500 16000 7000 17000 17000 Section 10000 10400 Top view 18000 5000 13300 Dimensions in mm Bus system Bypass bus

8000 28000 48000 10000

4000 4000 5000 Central tower layout with rotary

disconnectors, normally only for 245 kV The busbar disconnectors are arranged side by side and parallel to the longitudinal axis of the feeder. Wire-type busbars locat-ed at the top are commonly uslocat-ed; tubular busbars are also conceivable. This arrange-ment enables the conductors to be easliy jumpered over the circuit-breakers and the bay width to be made smaller than that of in-line designs. With three conductor levels the system is relatively clear, but the cost of the gantries is high (Fig. 11).

Diagonal layout with pantograph disconnectors, preferable up to 245 kV The pantograph disconnectors are placed diagonally to the axis of the busbars and feeder. This results in a very clear, space-saving arrangement. Wire and tubular con-ductors are customary. The busbars can be located above or below the feeder con-ductors (Fig. 12).

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Design of Air-Insulated Outdoor Substations

Fig.13 : 1 1_/ 2 Circuit-breaker design 1 1_/ 2 circuit-breaker layout, preferable up to 245 kV The 1 1_/

2 circuit-breaker arrangement

as-sures high supply reliability; however, ex-penditure for equipment is high as well. The busbar disconnectors are of the panto-graph, rotary and vertical-break type. Verti-cal-break disconnectors are preferred for the feeders. The busbars located at the top can be of wire or tubular type. Of advan-tage are the equipment connections, which are very short and enable (even in the case of multiple conductors) high short-circuit currents to be mastered. Two arrange-ments are customary:

■External busbar, feeders in line with three conductor levels

■Internal busbar, feeders in H arrange-ment with two conductor levels (Fig. 13).

Planning principles

For air-insulated outdoor substations of open design, the following planning princi-ples must be taken into account:

■High reliability

– Reliable mastering of normal and exceptional stresses

– Protection against surges and light-ning strikes

– Protection against surges directly on the equipment concerned (e.g. transformer, HV cable)

■Good clarity and accessibility – Clear conductor routing with few

conductor levels

– Free accessibility to all areas (no equipment located at inaccessible depth)

– Adequate protective clearances for installation, maintenance and transpor-tation work

– Adequately dimensioned transport routes

■Positive incorporation into surroundings – As few overhead conductors as

possible

– Tubular instead of wire-type busbars – Unobtrusive steel structures – Minimal noise and disturbance level

■EMC grounding system

for modern control and protection

■Fire precautions and environmental protection

– Adherence to fire protection speci-fications and use of flame-retardant and nonflammable materials – Use of environmentally compatible

technology and products

For further information please contact:

Fax: ++ 49 - 9131- 73 18 58 e-mail: [email protected] 29000 4000 Dimensions in mm 18000 17500 48000 8500

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General

Circuit-breakers are the main module of both AIS and GIS switchgear. They have to meet high requirements in terms of:

■Reliable opening and closing

■Consistent quenching performance with rated and short-circuit currents even after many switching operations

■High-performance, reliable maintenance-free operating mechanisms.

Technology reflecting the latest state of the art and years of operating experience are put to use in constant further develop-ment and optimization of Siemens breakers. This makes Siemens circuit-breakers able to meet all the demands placed on high-voltage switchgear. The comprehensive quality system, ISO 9001 certified, covers development, manufacture, sales, installation and after-sales service. Test laboratories are accred-ited to EN 45001 and PEHLA/STL.

Main construction elements

Each circuit-breaker bay for gas-insulated switchgear includes the full complement of isolator switches, grounding switches (regular or proven), instrument transform-ers, control and protection equipment, in-terlocking and monitoring facilities com-monly used for this type of installation (See chapter GIS, page 2/30 and following). Circuit-breakers for air-insulated switch-gear are individual components and are assembled together with all individual electrical and mechanical components of an AIS installation on site.

All Siemens circuit-breaker types, whether air or gas-insulated, are made up of the same range of components, i.e.:

■Interrupter unit

■Operating mechanism

■Sealing system

■Operating rod

■Control elements.

Fig. 14: Circuit-breaker parts

Circuit-breaker for air-insulated switchgear

Control elements

Circuit-breaker in SF6-insulated switchgear

Interrupter unit Operating

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Circuit-Breakers for 72 kV up to 800 kV

Interrupter unit –

two arc-quenching principles

The Siemens product range includes high-voltage circuit-breakers with self-compres-sion interrupter chambers and twin-nozzle interrupter chambers – for optimum switching performance under every operat-ing condition for every voltage level.

Self-compression breakers

3AP high-voltage circuit-breakers for the lower voltage range ensure optimum use of the thermal energy of the arc in the contact tube. This is achieved by the self-compression switching unit.

Siemens patented this arc-quenching prin-ciple in 1973. Since then, we have contin-ued to develop the technology of the self-compression interrupter chamber. One of the technical innovations is that the arc en-ergy is being increasingly used to quench the arc. In short-circuit breaking operations the actuating energy required is reduced to that needed for mechanical contact move-ment. That means the operating energy is truly minimized. The result is that the self-compression interrupter chamber allows the use of a compact stored-energy spring mechanism with unrestrictedly high de-pendability.

Twin-nozzle breakers

On the 3AQ and 3AT switching devices, a contact system with graphite twin-nozzles ensures consistent arc-quenching behavior and constant electric strength, irrespective of pre-stressing, i.e. the number of breaks and the switched current. The graphite twin-nozzles are resistant to burning and thus have a very long service life. As a consequence, the interrupter unit of the twin-nozzle breaker is particularly powerful.

Moreover, this type of interrupter chamber offers other essential advantages. General-ly, twin-nozzle interrupter chambers oper-ate with low overpressures during arc-quenching. Minimal actuating energy is adequate in this operating system as well. The resulting arc plasma has a compara-tively low conductivity, and the switching capacity is additionally favourably influ-enced as a result.

The twin-nozzle system has also proven itself in special applications. Its specific properties support switching without re-striking of small inductive and capacitive currents. By virtue of its high arc resist-ance, the twin-nozzle system is particularly suitable for breaking certain types of short circuit (e.g. short circuits close to genera-tor terminals) on account of its high arc re-sistance.

Operating mechanism –

two principles for all

specific requirements

The operating mechanism is a central mod-ule of the high-voltage circuit-breakers. Two different mechanism types are availa-ble for Siemens circuit-breakers:

■Stored-energy spring actuated mechanism,

■Electrohydraulic mechanism,

depending on the area of application and voltage level, thus every time ensuring the best system of actuation. The advantages are trouble-free, economical and reliable circuit-breaker operation for all specific re-quirements.

Specific use of the stored-energy spring mechanism

The actuation concept of the 3AP high-volt-age circuit-breaker is based on the stored-energy spring principle. The use of such an operating mechanism in the lower voltage range became appropriate as a result of development of a self-compression inter-rupter chamber that requires only minimal actuation energy.

Advantages of the stored-energy spring mechanism at a glance:

■ The stored-energy spring mechanism of-fers the highest degree of operational safety. It is of simple and sturdy design – with few moving parts. Due to the self-compression principle of the inter-rupter chamber, only low actuating forc-es are required.

■ Stored-energy spring mechanisms are readily available and have a long service life: Minimal stressing of the latch mech-anisms and rolling-contact bearings in the operating mechanism ensure reliable and wear-free transmission of forces.

■ Stored-energy spring mechanisms are maintenance-free: the spring charging gear is fitted with wear-free spur gears, enabling load-free decoupling.

Specific use of the electrohydraulic mechanism

The actuating energy required for the 3AQ and 3AT high-voltage circuit-breakers at higher voltage levels is provided by proven electrohydraulic mechanisms. The inter-rupter chambers of these switching devic-es are based on the graphite twin-nozzle system.

Advantages of the electrohydraulic mechanism at a glance:

■ Electrohydraulic mechanisms provide the high actuating energy that makes it pos-sible to have reliable control even over very high switching capacities and to be in full command of very high loads in the shortest switching time.

■ The switch positions are held safely even in the event of an auxiliary power failure.

■ A number of autoreclosing operations are possible without the need for recharging.

■ Energy reserves can be reliably con-trolled at any time.

■ Electrohydraulic mechanisms are mainte-nance-free, economical and have a long service life.

■They satisfy the most stringent require-ments regarding environmental safety. This has been proven by electrohydraulic mechanisms in Siemens high-voltage circuit-breakers over many years of serv-ice.

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Fig. 15: The interrupter unit

The interrupter unit

The current path

The current path is formed by the terminal plates (1) and (8), the contact support (2), the base (7) and the moving contact cylin-der (6). In closed state the operating cur-rent flows through the main contact (4). An arcing contact (5) acts parallel to this.

Major features:

■ Self-compression interrupter chamber

■ Use of the thermal energy of the arc

■ Minimized energy consumption

■ High reliability for a long time Siemens circuit-breakers for the lower

voltage levels 72 kV up to 245 kV, whether for air-insulated or gas-insulated switch-gear, are equipped with self-compression switching units and spring-stored energy operating mechanisms.

Breaking operating currents

During the opening process, the main con-tact (4) opens first and the current commu-tates on the still closed arcing contact. If this contact is subsequently opened, an arc is drawn between the contacts (5). At the same time, the contact cylinder (6) moves into the base (7) and compresses the quenching gas there. The gas then flows in the reverse direction through the contact cylinder (6) towards the arcing con-tact (5) and quenches the arc there. Breaking fault currents

In the event of high short-circuit currents, the quenching gas on the arcing contact is heated substantially by the energy of the arc. This leads to a rise in pressure in the contact cylinder. In this case the energy for creation of the required quenching pres-sure does not have to be produced by the operating mechanism.

Subsequently, the fixed arcing contact re-leases the outflow through the nozzle (3). The gas flows out of the contact cylinder back into the nozzle and quenches the arc.

Closed position Open position

Terminal plate Contact support Nozzle Main contact Arc contact Contact cylinder Base Terminal plate 1 2 3 4 5 6 7 8 8 7 6 5 4 3 2 1 Opening

Main contact open

Opening

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Circuit-Breakers for 72 kV up to 245 kV

The operating mechanism

Siemens circuit-breakers for voltages up to 245 kV are equipped with spring-stored en-ergy operating mechanisms. These drives are based on the same principle that has been proving its worth in Siemens low and medium-voltage circuit-breakers for dec-ades. The design is simple and robust with few moving parts and a vibration-isolated latch system of highest reliability. All com-ponents of the operating mechanism, the control and monitoring equipment and all terminal blocks are arranged compact and yet clear in one cabinet.

Depending on the design of the operat-ing mechanism, the energy required for switching is provided by individual com-pression springs (i.e. one per pole) or by springs that function jointly on a triple-pole basis.

The principle of the operating mechanism with charging gear and latching is identical on all types. The differences between mechanism types are in the number, size and arrangement of the opening and clos-ing sprclos-ings.

Major features at a glance

■Uncomplicated, robust construction with few moving parts

■Maintenance-free

■Vibration-isolated latches

■Load-free uncoupling of charging mechanism ■Ease of access ■10,000 operating cycles Fig. 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Corner gears Coupling linkage Operating rod Closing release Cam plate Charging shaft Closing spring connecting rod Closing spring Hand-wound mechanism Charging mechanism Roller level Closing damper Operating shaft Opening damper Opening release Opening spring connecting rod Mechanism housing Opening spring 1 2 3 4 5 6 7 8 18 17 16 15 14 13 12 11 10 9

Fig. 17: Combined operating mechanism and monitoring cabinet

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■Erosion-resistant graphite nozzles

■Consistently high dielectric strength

■Consistent quenching capability across the entire performance range

■High number of short-circuit breaking operations

■High levels of availability

■Long maintenance intervals.

The interrupter unit

Current path assembly

The conducting path is made up of the terminal plates (1 and 7), the fixed tubes (2) and the spring-loaded contact fingers arranged in a ring in the moving contact tube (3).

Fig. 18: The interrupter unit

Siemens circuit-breakers for the higher voltage levels 245 kV up to 800 kV, wheth-er for air-insulated or gas-insulated switch-gear, are equipped with twin-nozzle inter-rupter chambers and electrohydraulic operating mechanisms.

Arc-quenching assembly

The fixed tubes (2) are connected by the contact tube (3) when the breaker is closed. The contact tube (3) is rigidly cou-pled to the blast cylinder (4), the two to-gether with a fixed annular piston (5) in between forming the moving part of the break chamber. The moving part is driven by an operating rod (8) to the effect that the SF6 pressure between the piston (5)

and the blast cylinder (4) increases. When the contacts separate, the moving contact tube (3), which acts as a shutoff valve, releases the SF6. An arc is drawn

between one nozzle (6) and the contact tube (3). It is driven in a matter of millisec-onds between the nozzles (6) by the gas jet and its own electrodynamic forces and is safely extinguished.

The blast cylinder (4) encloses the arc-quenching arrangement like a pressure chamber. The compressed SF6 flows

ra-dially into the break by the shortest route and is discharged axially through the noz-zles (6). After arc extinction, the contact tube (3) moves into the open position. In the final position, handling of test volt-ages in accordance with IEC 60 000 and ANSI is fully assured, even after a number of short-circuit switching operations.

1 2 3 6 4 5 2 8 7 Arc Breaker in closed position

Precompression Gas flow during arc quenching Breaker in open position Upper terminal plate Fixed tubes Moving contact tube Blast cylinder Blast piston Arc-quenching nozzles Lower terminal plate Operating rod 1 2 3 4 5 6 7 8

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The operating mechanism

All hydraulically operated Siemens circuit-breakers have a uniform operating nism concept. Identical operating mecha-nisms (modules) are used for single or tri-ple-pole switching of outdoor circuit-breakers.

The electrohydraulic operating mecha-nisms have proved their worth all over the world. The power reserves are ample, the switching speed is high and the storage capacity substantial. The working capacity is indicated by the permanent self-monitor-ing system.

The force required to move the piston and piston rod is provided by differential oil pressure inside a sealed system. A hydrau-lic storage cylinder filled with compressed nitrogen provides the necessary energy. Electromagnetic valves control the oil flow between the high and low-pressure side in the form of a closed circuit.

Main features:

■Plenty of operating energy

■Long switching sequences

■Reliable check of energy reserves at any time

■Switching positions are reliably maintained, even when the auxiliary supply fails

■Excessive strong foundations

■Low-noise switching

■No oil leakage and consequently environmentally compatible

■Maintenance-free. Description of function

■Closing:

The hydraulic valve is opened by elec-tromagnetic means. Pressure from the hydraulic storage cylinder is thereby ap-plied to the piston with two different surface areas. The breaker is closed via couplers and operating rods moved by the force which acts on the larger sur-face of the piston. The operating mech-anism is designed to ensure that, in the event of a pressure loss, the breaker remains in the particular position.

Fig. 21: Schematic diagram of a Q-range operating mechanism

■Tripping:

The hydraulic valve is changed over electromagnetically, thus relieving the larger piston surface of pressure and causing the piston to move onto the OFF position. The breaker is ready for instant operation because the smaller piston surface is under constant pres-sure. Two electrically separate tripping circuits are available for changing the valve over for tripping.

Circuit-Breakers for 245 kV up to 800 kV

Fig. 19: Operating unit of the Q range AIS circuit breakers

Fig. 20: Operating cylinder with valve block and magnetic releases M P P M Oil tank Hydraulic storage cylinder Operating cylinder Releases Operating piston Pilot control On Off N2 Main valve Auxiliary switch Monitoring unit and hydraulic

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Fig. 23: 800 kV circuit-breaker 3AT5

Fig. 24: 245 kV circuit-breaker 3AQ2

Fig. 22: 145 kV circuit-breaker 3AP1FG with triple-pole spring stored-energy operating mechanism

Circuit-breakers

for air-insulated switchgear

Standard live-tank breakers

All live-tank circuit-breakers are of the same general design, as shown in the illus-trations. They consist of the following main components:

1) Interrupter unit

2) Closing resistor (if applicable) 3) Operating mechanism 4) Insulator column (AIS) 5) Operating rod 6) Breaker base 7) Control unit

The uncomplicated design of the breakers and the use of many similar components, such as interrupter units, operating rods and control cabinets, ensure high reliability because the experience of many breakers in service has been applied in improvement of the design. The twin nozzle interrupter unit for example has proven its reliability in more than 60,000 units all over the world. The control unit includes all necessary devices for circuit-breaker control and mon-itoring, such as:

■Pressure/SF6 density monitors ■Gauges for SF6 and hydraulic pressure

(if applicable)

■Relays for alarms and lockout

■Antipumping devices

■Operation counters (upon request)

■Local breaker control (upon request)

■Anticondensation heaters.

Transport, installation and commissioning are performed with expertise and effi-ciency.

The tested circuit-breaker is shipped in the form of a small number of compact units. If desired, Siemens can provide appropriately qualified personnel for instal-lation and commissioning.

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Live-Tank Circuit-Breakers for 72 kV up to 800 kV

Fig. 26: Type 3AP1FG Fig. 25: Type 3AT4/5

Fig. 27: Type 3AQ2 1 Interrupter unit 2 Closing resistor 3 Valve unit 4 Electrohydraulic operating mechanism 5 Insulator columns 6 Breaker base 7 Control unit 1 5 3 4 7 6 2 1 Interrupter unit 2 Post insulator 3 Circuit-breaker base 4 Operating mechanism

and control cubicle

5 Pillar 5 4 3 2 1 Interrupter unit Arc-quenching nozzles Moving contact Filter Blast piston Blast cylinder Bell-crank mechanism Insulator column Operating rod

Hydraulic operating mechanism ON/OFF indicator Oil tank Control unit 12 9 8 10 11 4 13 6 5 3 7 2 1 1 2 3 4 5 6 7 8 9 10 11 12 13