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Gas-Insulated lInes (GIl) Choices today and tomorrow

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Contents

THINK GRID – SHARING ALSTOM GRID INNOVATION & PRACTICES – Published by Alstom Grid - 1 place Jean Millier - 92084 La Défense - France. www.alstom.com/grid - Print run: 16,000 copies (Chinese, English, French, German, Spanish) - Publisher: Peter Kirchesch - Editor in chief: Véronique Chauvot - Editorial assistant: Charlotte Defrel - Editorial board: Philippe Ponchon, Milan Saravolac, François Gallon, Greg Manning, Xavier Hurbin - Concept and Design: BythewayCreacom - 19 rue Galilée, 75116 Paris - France - Tel.: +33 (0)1 53 57 60 60 - www.bythewaycreacom.net - Editorial executive: Henry Lewis Blount - Publication manager: Kaling Chan - Contributors: Henry Lewis Blount, Ken Kincaid, Patrick Love, Louis-Antoine Mallen, Anne Träger - Copy editor: Ginny Hill - Art director: Didier Trayaud - Computer graphics artist: Jean-Marie Lagnel - Photo credits: Pagasus, Minko Stelzer, Flicker, David Min, Peter Gridley / Getty Images, Pete Webb / Masterfile, Catherine de Torquat, John Framm / Hemis, Ocean / Corbis, EWEA, Alstom, Areva - Printing: Lecaux. ISSN: 2102-0175. A special thanks to the companies that kindly provided us with their illustrations.

063D training

12Respectingthe environmentGas-insulated lines (GIL): Choices today and tomorrow

Interview with Christian Lindner 08

#07 Summer 2010

33Smart products & servicesMonitoring systems: From raw beginners to expert communicators

Electricity lore A short history of distance protection

46

23Innovation & performanceMulti-terminal HVDC system for large offshore wind park grid integration

5 FOREWORD By Prof. Peter Kirchesch: R&D Vice-President, Alstom Grid

6 PANORAMA 3D training

8 INTERVIEW WITH… Christian Lindner of the Swiss utility Axpo

11 MAIN FEATURE Pushing the frontiers of electricity technology

12 Chapter I Respecting the environment Research with an eye on the future

23 Chapter II Innovation & performance Ahead of our time

33 Chapter III Smart products & services Making energy available to all, today and tomorrow

44 CROSS-PERSPECTIVES The importance of intellectual property

46 ELECTRICITY LORE A short history of distance protection

50 FURTHER READING Books, newspapers, etc.

51 DATES FOR YOUR DIARY Don’t miss...

Respectingthe environmentGas-insulated lines (GIL): Choices today and tomorrow

Think Grid

4 Alstom Grid///Summer 2010

Alstom Grid///Summer 2010 5

Gas-insulated lines (GIL):

A promising alternative

Electricity consumption is forecast to increase by 50 percent between now and 2030. To meet this growing demand, additional power plants are under construction all over the world.

Often these power plants can only be erected at sites remote from the load centers, so the electricity has to be transported to end users. This is achieved by transmission networks, which have to transport the energy as efficiently as possible and at the same time take economic factors, network safety and redundancy into account.

The most common and generally lowest-cost method to transport bulk power over long distances is via overhead lines. But densely populated areas or environmentally sensitive regions call for alternative solutions. Typically, underground transmission systems are the answer and power cables the prevailing technology. However, the gas-insulated line (GIL) is an alternate solution for underground transport of electricity at high transmission ratings. GIL is also an attractive solution where cables cannot be used or where they have reached their technical limits. A potential application is the transport of electrical energy from offshore wind parks to the mainland electricity grid.

In the past decade, huge progress has been made in developing GIL as a reliable, cost-effective transmission system. This issue of Think Grid takes a closer look.

FOREwORDBy Prof. Peter Kirchesch: R&D Vice-President, Alstom Grid

on June 6, 2010, AreVA T&d Joined

AlsTom And sChneider

eleCTriC To CreATe Two GlobAl

enerGy leAders. Our Senior Experts and

their teams will continue to shape the future of the power grids in their new

companies. Our magazine Think T&D is

now published by Alstom under its new name

Think Grid.


PAnorAmA

S A l e S S n A P S h o t SUnited Kingdom December 2009

3D training

GeRMAnYThe latest innovative wind farm projectAlstom Grid and Dutch consortium partner Keppel Verolme B.V. have been awarded an order for an Offshore High Voltage Substation (OHVS) by the German wetfeet Offshore windenergy GmbH. It is a turnkey project to supply a self-floating, self-installing 155/33 kV OHVS to connect Wetfeet’s offshore wind farm in the North Sea to the German grid. During installation and operation, the platform will also act as a logistics service base equipped with boat landings, a helicopter deck and accommodations.

InDIAGIS and GILBharat Heavy Electricals (BHEL), the largest engineering and manufacturing company in India’s energy sector, has awarded Alstom Grid a contract for a gas-insulated substation (GIS). The 420 kV and 230 kV GIS will be installed end-2010 at the Tamil Nadu state utility’s North Chennai Thermal Power project and will include the engineering and supply of eight B105 bays and 14 T155 bays as well as around 1.5 km of gas-insulated lines (GIL).

AUStRAlIA The largest ever infrastructure project in Australia Alstom Grid together with Schneider Electric Energy have been awarded an order for the Gorgon Liquefied Natural Gas (LNG) project, considered to be the largest infrastructure development in Australia to date. The project will extract gas from the Greater Gorgon gas fields, located 130 km off the north-west coast of Australia. The order is for containerized substations including 132 kV gas-insulated substations (GIS), MV switchgear, LV switchgear and motor control centers for the project’s entire electrical system.

BRAZIl The world’s longest DC power transmission project Alstom Grid has won an order to connect the Porto Velho collector substation in the Amazon region with the Araraquara Substation II in Sao Paulo. The project is part of a power transmission plan to connect the Madeira river’s Jirau and Santo Antonio hydroelectric power stations (6,300 MW) to the Brazilian national grid over 2,375 km of overhead lines. Alstom Grid will contribute its 600 kV HVDC technology manufactured in Brazil and the U.K.

CAnADAImproving network efficiencyHydro Québec, Quebec’s major utility, has awarded Alstom Grid the contract to engineer, supply, install and commission two 660 MVAr, 735 kV Fixed Series Compensation systems at their Jacques Cartier substation, north of Quebec City. The contract includes delivery of capacitor banks, varistors, spark gaps, by-pass breakers, current transformers, and control and protection cubicles. The major components will be produced by the Tampere facility in Finland.

The Alstom Grid Technical Institute has formed a partnership with National Grid in the U.K. to develop 3D training modules.

National Grid decided it needed an innovative approach to training its staff on T155 gas-insulated substations. So it joined forces with Alstom Grid in seeking a forward-looking solution.

Alstom Grid had already developed 3D materials of its products for some exhibitions. At the 3D showroom of its Technical Institute in Stafford, U.K. and its Technical Institute at Aix-les-Bains in France, the company showcased what value 3D could add to training customers.

The 3D training modules for the T155 GIS to be used at National Grid’s training center in Eakring, U.K. will be the first in the T&D industry. Their introduction will reinforce the acknowledged technological leadership of both National Grid and Alstom Grid. As John Tyler, National Grid Training Delivery Manager, points out, “The collaboration between National Grid and Alstom Grid demonstrates that both companies are forward-looking and have ambitions to provide cutting-edge learning solutions.”


Power frequencies worldwide

POwER FREqUENCIES wORLDwIDE

today, electricity is nearly exclusively transmitted at a frequency of 50 Hz or 60 Hz. But it was not always so. Many frequencies were used throughout the development of electrical power systems, from 16 2/3 Hz to 140 Hz. This was pos-sible when grids were operated in isolation. with network interconnection, standard-ization became a must, because generators can only operate in parallel if they are of the same frequency and wave-shape.

The ideal frequency is a compromise between contradictory requirements. A relatively high frequency was needed to economize on transformer materials, whereas a low frequency is preferable for long transmission lines.In the late 19th century, one of Alstom Grid’s parent companies, AEG, built the first German generating facility to run at 50 Hz. At the time, AEG had a virtual monopoly and the standard spread across

Europe. In the Americas, standardization ended up with a 60 Hz system, mainly driven by the dominating role of west-inghouse Electric.There is no technical reason to prefer one over the other. Some countries still don’t. In Japan, the eastern part of the country uses 50 Hz and the west 60 Hz. The rea-son is simple. AEG installed the first gen-erators in 1895 in Tokyo and General Electric in 1896 in Osaka.

I n F I G U R e S

Power frequencies worldwide

50 Hz

60 Hz

50 and 60 Hz


inTerView wiTh…

Axpo lives and breathes sustainability and this is reflected in our vision.


Axpo is a major utility in Switzerland. What are the main challenges you will be facing in the coming years?Christian lindner: Axpo is an energy pro-vider that thinks very long term. Our core business—energy generation, transmission, distribution and trading—affects the econ-omy, the environment and society at large. we are public-service oriented as well as having financial targets. All this obliges us to act “sustainably.” Axpo considers reliable energy provision as its core service in Switzerland, under-pinned by broad product diversification and a smoothly operating network. we give operating and occupational safety pride of place and strive continuously to enhance our safety culture while minimiz-ing our burden on people and the environ-ment.

Switzerland, Zürich. View of city, lake and Limmat river.

Switzerland, Zürich. Swiss National Day (August 1).

Axpo head office in Baden, Switzerland.

What is Axpo’s position on sustainability?C.l.: Axpo lives and breathes sustainability, which is reflected in our vision of “reliable, sustainable and innovative.” Our commit-ment to sustainability is not an objective per se, because we believe that if we work toward sustainability we will be a more suc-cessful company. Axpo has done much, and continues to do so, to make the notion of sustainability a concrete one. we have dedicated personnel, acquired the necessary knowledge, and built an organization and processes to cement sustainable actions and reflexes.Our employees are expected to develop a common understanding of sustainability through continuous processes and appreci-ate why sustainability is important for the company. we have set appropriate qualita-tive and quantitative objectives.

How “green” are Axpo’s products and services?C.l.: we asked ourselves this question when defining and acquiring high voltage products for installing substations. we decided to link technology and environmental consid-erations more closely and to develop and integrate ecological criteria in our require-ments. Consequently, environmental aspects were included in our requests for tender for HV equipment. For example, special environmental parameters were included, or suppliers agreed to state the environmental credentials of their products as proof that they meet our requirements. The first example of requests for tender link-ing technology and environment was the acquisition of the GIS for the Münchwilen (110 kV) and Schlattingen (110/220 kV) substations. we identified and subse-quently assessed environmental

Christian lindner of the Swiss utility Axposhares his practical experience with environmentally friendly products.


had differentiation of the HV products through individual parameters such as SF6 losses or heat losses. But we wanted to know more, and we discovered that several suppliers used an analysis of environmen-tal impact of switchgear during its entire life cycle. This more in-depth analysis enabled us to compare the different HV system offerings based on their environmental footprint and, consequently, influence product selection.An additional target of this environmental analysis was to identify comparable envi-ronmental parameters with our suppliers and include them in the specifications. This eventually resulted in a new chapter

aspects such as global warming potential (from product cradle to grave), direct and indirect greenhouse gas emis-sions through gas or heat loss during operation, as well as specific raw material usage during product manufacturing. It is worth noting that, specifically for high voltage products, the usage phase is responsible for around 90 percent of the environmental impact because of their long life cycle of some 60 years.By homing in on environmental aspects of switchgear, you tend to develop an environ-mental awareness not only in your profes-sional activity but also in your private life.

About a year ago, you launched an environmental evaluation of a 245 kV substation with different suppliers. Could you tell us more about that study? What were/are Axpo’s expectations?C.l.: Our strategic objective was to inti-mately link environment and technology. The environmental impact of our switch-gear during its operational life had always been an important point. we were keen to understand how we could make the choice of technology dependent on environmen-tal concerns. At first, before we carried out in-depth environmental analyses, we only

dedicated to the environment in our prod-uct specifications.

Do you believe such an Environmental Life Cycle Assessment will become a standard in the future? C.l.: In the interests of the human race and the environment, I hope, of course, that life cycle analysis will be increasingly used and that not only Axpo but also other energy providers will take up the subject. It doesn’t have to become a standard. It should simply enhance environmental awareness. That would already be a big step forward.

inTerView wiTh…

By homing in on environmental aspects of switchgear, you tend to develop an environmental awareness also in your private life.

The chart shows that environmental aspects are taken into consideration from the design phase right up to the final product order.

hV SYSteM enGIneeRInG PRoCeSS

order

Specification and call for tender

Environmental parameters in Axpo specs

• Weight• SF6 losses• SF6 volumes• Energy losses• Recyclability• GWP (optional)

offer analysis

Selection criteria

• 50 points price

• 40 points technology and environment

• 10 points references, service

design selectionin pre-project phase

Environmental parameters examined

• Global warming potential in CO2 equivalent

• Footprint• Weight• SF6 losses• Heat losses• Recyclability

Pushing the frontiers of electricity technology

12 Chapter IRespecting the environment

23 Chapter IIInnovation and performance

33 Chapter IIISmart products and services

mAin FeATure


Respecting the environmentLow power losses and a lesser visual impact on the landscape make gas-insulated lines (GIL) a very environmentally friendly transmission solution compared to overhead lines. Alstom Grid’s eco-design makes them even more so. Power electronics also have great environmental credentials as distributed energy sources become more widespread. Meanwhile, ester oils have proved their value in distribution transformers; research is now focusing on overcoming the challenges to their potential for power transformers.

Main feature chapter I research wIth an eye on the future



Gas-insulated lines (GiL): Choices today and tomorrowthanks to their high transmission capacities and reliability, GIL have been in use for over four decades in power plants and substations. they are now considered as an efficient alternative to cables or overhead lines in a growing number of applications.

ing from a few meters to 900-1,000 meters. Directly laid on the soil or in trenches or tun-nels, they have seen their field of application widen (and lengthen) to stand-alone instal-lations up to several kilometers for resolving specific environmental, routing access or right-of-way issues. GIL provide an effective technological answer to the increasing energy needs of our urban society and to the exten-sion and reinforcement of the present elec-tricity transmission and distribution networks. transmitting bulk power over short and long

Gas-insulated lines are a transmission technology developed in the late 1960s for use in substations, hydro power plants, underground facilities, and so on. their high transmission capacity (up to 3,000 MVa through one GIL circuit) and multiple achievable configurations offer important advantages for transmitting bulk electric power in such complex sites. In substations, for instance, GIL serve as connections between GIs switchgear and power trans-formers or overhead lines, at distances rang-

distances in a safe and environmentally friendly way represents one of the major challenges of the coming decades; GIL is a key to solve this issue.

Electric pipelinesencapsulated in a 400 to 600 mm diam-eter metallic case, gas-insulated lines bear a resemblance to pipelines. originally devel-oped for GIs connections, GIL have similar bus sections and busbar arrangements. the “electric pipeline” consists mainly

Encapsulated in a 400 to 600 mm diameter metallic case, gas-insulated lines bear a resemblance to pipelines.



of a pair of tubular aluminum coax-ial conductors, the inner one being at the high voltage level and the outer one being earthed. to ensure insulation, the space between the enclosure and the conductor is filled with sulfur hexafluoride (SF6) or a pressurized gas mixture of nitrogen and sf6. “with their very high conductor cross-section, GIL are designed for high transmis-sion capacities with rated currents typically reaching 4,000 a at 550 kV, and a short-circuit current capability up to 63 ka,” explains Mathieu Bernard, GIL project Man-ager. this offers multiple advantages: GIL combine low capacitance (and therefore very low transmission losses), high reli-ability, and operational safety thanks to a robust casing and the fact that they are inherently fireproof. Another benefit is their long lifetime—up to 50 years—with virtually no material ageing. Moreover, “thanks to reduced space requirements and flexible route capabilities, GIL are adapted to solve

complex geographic installation issues like hydroelectric power plants in new or exist-ing underground conditions,” Bernard adds. one drawback, how-ever, is their cost, which is still relatively high when compared to overhead lines (five to seven t imes more expensive). In fact, GIL are not designed to compete with overhead lines everywhere but rather as a means of power transmission where ohL cannot or must not be applied.

High service continuitySince their first application some 40 years ago, more than 250 km of three-phase GIL systems have been installed in the world (750 km of single-phase pipes). they oper-ate at different voltage levels between

72.5 kV and 800 kV (mainly at the 420 kV level), and demand has significantly increased over the past few years. at alstom

Grid alone, over 50 km of three-phase circuits have been installed or ordered since the beginning of GIs pro-duction, including 30 km over the last 12 years, showing clear acceleration. almost maintenance-free and with low

operating costs, GIL are now widely recog-nized as a well-proven technology with a long service record and a high level of reli-ability. even so, “modern digital monitoring systems help further improve their reliability and service continuity,” says françois Biquez, senior expert r&D Manager for GIS-GIL. Digital sensors and optical fiber transmission enable the real-time monitor-

GIL combine low capacitance, high reliability and operational safety.

The T155 gas-insulated substation installed at Shuqaiq, Saudi Arabia, a major Alstom Grid reference demonstrating that the company can offer a whole range of flexible GIL solutions.


ing of parameters such as sf6 or gas mixture density, sf6 leakage trend analysis, tem-peratures in compartments, partial dis-charges, internal arc localization and detection, etc. abnormal conditions that could lead to potential failures are therefore rapidly detected. as a result, safety for per-

sonnel and switchgear is enhanced, as well as security and quality of power supply, protection of the environment (against sf6 leakages), asset management (maintenance and outage planning, integration in a digi-tal control system), operational profitability due to energy deregulation requiring more rapid and accurate data management, and so on.on the other hand, today’s computerized design tools offer the ability to adapt GIL to severe operating conditions. for each particular installation, calculations can be made to select the right solution and ensure optimal working conditions while adhering to strict regulatory standards. “the dimensioning of a GIL clearly depends on its dielectric withstand performance and on its thermal capability to carry the rated current,” explains Biquez. “as the thermal limits of the product are affected by the way the GIL is installed, computer simulations are necessary to decide on the appropriate design.” In the case of an underground hydro power plant, thermal simulations have enabled alstom Grid’s designers to evaluate the thermal behavior of the GIL enclosure as a function of the tunnel height, or to compare the conductor and enclosure temperature distribution depending on whether the GIL is placed in a horizontal tunnel or a vertical shaft.

Higher environmental efficiencyopting for a GIL solution brings major envi-ronmental benefits. The first is that, thanks to a very low capacitance, the electrical resis-tance and power losses of GIL are extremely reduced—up to 70 percent lower than

teChniCaL benefits of GiL CoMpared with CabLes at haMs haLL The 420 kV Hams Hall substation in the West Midlands, England, required a new connection to reinforce the network. However, existing overhead lines and buried cables and pipes demanded that the connection be in trenches at the one end and above ground at the other end. Both GIL and cables offered suitable solutions. However, for both technical and economic reasons, the British utility National Grid adopted the Alstom Grid GIL solution. “A continuous current rating of 3,190 A would have required two cables with two outdoor terminations per phase compared with one GIL,” says Alain Girodet, Senior Expert, Alstom Grid High Voltage Technology and Materials Manager. “Cable junctions would also have been more of an issue from a dielectric perspective,” he adds. To minimize environmental risks with GIL, an insulating gas mixture made of 20 percent SF6 and 80 percent N2 was chosen, as well as a totally welded pipe design (which required special care in the assembly process to avoid weld slags seeping inside the GIL). Another advantage is that the N2/SF6 mixture can be easily separated and recycled after use.

M o r EAlain Girodet

HiGH SErvicE continuity



interview with Gerhard seyrLinG, senior viCe-president innovation & strateGy

What is Alstom Grid’s experience with GiL?Alstom Grid has long experience with GIL design and installation, especially for large power sites. One of our major references is the PP9 project in Saudi Arabia: with total circuit lengths of approximately 5.6 km, more than 17 km of single-phase enclosures were necessary (see figure on page 17). Alstom Grid has developed and masters a whole range of

flexible solutions, using bolted or welded connections and various insulating gas mixtures to optimize cost, performance, reliability and environmental protection.

How can GiL compete against overhead lines and cables?GIL have proved their ability to respond to any installation constraints as well as carrying high power ratings without requiring multiple circuit configurations. Compared to overhead lines, the major advantage is better integration in the urban environment and landscapes. Compared with cables, GIL can transmit greater quantities of energy: 3,000 MVA can be transmitted

through one GIL circuit while two circuits would be required for the alternative HV cable solution; this performance has a direct impact on price, footprint and right-of-way requirements.

What are customers looking for?Besides substations, customers have to find answers to two types of issues. One is carrying high rated currents in urban areas where OHL are prohibited; the other is to ensure regional and international bulk power connections with GIL offering a safe, flexible, aesthetic and powerful solution through tunnels, bridges, and so on.

M o r EGerhard Seyrling

those of overhead lines (ohL). this means less waste of energy, and no need for reactive compensation for lengthy GIL, con-trary to long cable connections. another advantage is a lower visual impact on the landscape, suggesting that GIL may be a realistic solution in sites where ohL would be banned. a costly solution, indeed—but “the expense may be worth it,” one chief executive of a u.s. transmission company pointed out recently, as OHL become “infi-nitely expensive” if their construction is resolutely opposed by local communities.to minimize the environmental impact of its GIL solutions, alstom Grid has imple-mented an eco-design approach, as for a number of its products. the latest designs are nowadays completely optimized in a sustainable development perspective. the whole life of the product is considered, from “cradle to grave.” It starts with a life cycle assessment (LCA), which identifies and quantifies all the environmental impacts encountered when manufacturing and using the GIL, from raw material extraction and transportation to the disposal of the product at the end of its life. up to 16 indi-cators are used, showing the impact of the various steps of the product life cycle on features such as global warming, ozone depletion, acidification, eco- and human

firewall between a burning oil transformer and a GIs, thus preventing the fire from spreading and allowing the rest of the system to stay operational. Thanks to these fire- and explosion-proof characteristics, GIL can be installed in shared infrastructure like road and rail tunnels, open public areas, etc. an illustration of an in-public area installation of a GIL is the hams hall project in the u.K., which was energized in 2004 (see sidebar). Another powerful benefit of GIL in public area installations is their low magnetic field radiation emission. cross-bonding of single-phase enclosures allows the return current to pass through the enclosures. this creates a screen effect that provides the GIL with a lower magnetic field radiation compared with alternative solutions such as cables and ohL. computer calculations show that mag-netic field values at the enclosure of a three-phase GIL system (operating at 550 kV and 4,000 a) are lower than 250 µt, half the exposure limit for workers set by the euro-pean union directive. at a distance of 1 meter to the enclosure, the value drops to 10 µt, less than one-tenth the emission of buried XLpe cables 1 meter above ground level, and less than a quarter of overhead lines (below the lines at 1 meter above ground level). In fact, GIL enclosures can even be safely touched.

toxicity, hazardous waste, amount of slag/ashes, etc. each component of a GIL may then be optimally designed to achieve maximum environmental efficiency, thus contributing to a moderate and responsible use of the needed resources, and ensuring a high recyclability rate. “the latest devel-opments have led, for instance, to a more environmentally fr iendly insulation medium: the amount of greenhouse effect sf6 gas produced has been dramatically reduced through the use of a gas mixture based on 80-90 percent of nitrogen and the rest of sf6,” says Biquez. alstom Grid was also able to optimize the section of the conductors, enabling the GIL to exhibit lower heat losses compared with ohL and hV cables.

Ensuring safety for peopleas high voltage power transmission lines may be set up in any kind of configuration, even in crowded public areas, the safety of the surroundings is essential. thanks to the design of their aluminum enclosures, GIL completely exclude the risk of explosion. Moreover, the total absence of inflammable materials (such as oil) makes the GIL abso-lutely fire-safe, hence no smoke is emitted even in the case of an electrical fault; the GIL will even play the role of a buffer or


Alstom Grid has installed (or received orders for) more than 50 kilometers of three-phase GIL systems since the beginning of GIS production and 30 km in the past 12 years. Prime examples of this success are the Jebel Ali power plant in the United Arab Emirates, Shuqaiq in Saudi Arabia, and the Hams Hall substation in the West Midlands, U.K.


Functionalities of active networks

400

V10

-10

0 kV

150

kV22

0…76

5+ k

V

Asynchronousinterconnection

Customizedinterface

RES interface

RES interface

D-STATCOM

Fast car charger

Car charger

Electronic transformer

Series powerflow controller

Series powerflow controllerElectronic

transformer

Storageinterface

Multi-terminalDC distribution

Main Feature chapter I research wIth an eye on the future

since the 1980s, power electronics have found any number of applications, from improving network characteristics where heavy industries connect to weak grids, to flexible AC transmission systems (FACTS) and high voltage Dc transmission. however, for now, they are largely absent from electri-cal distribution systems, due in part to the traditional configuration based on large, remote power plants. not so in the future, explains Patrick Favre-Perrod, of Strategy and collaborative Development, alstom Grid research and technology centre in stafford, u.K. “renewable sources have very aggres-sive profiles that can vary from 0 percent to

Power electronics and the future of

distribution networksGreener may just be meaner, at least on the

distribution grid. stochastic renewable sources and increased electrical consumption will require solutions for maintaining

service levels, voltage quality and system availability. this is a job for power electronics.

The ubiquiTy of power elecTronics


Functionalities of active networks

400

V10

-10

0 kV

150

kV22

0…76

5+ k

V

Asynchronousinterconnection

Customizedinterface

RES interface

RES interface

D-STATCOM

Fast car charger

Car charger

Electronic transformer

Series powerflow controller

Series powerflow controllerElectronic

transformer

Storageinterface

Multi-terminalDC distribution

100 percent in a short period of time. and electric vehicles and electric heating, con-sequences of energy systems becoming greener, will be demanding on the grid.” as a result, power electronics will necessarily be part of future solutions to operate the distribution network, maintain voltage pro-files across the board and ensure stability.

The push to power electronics“future distribution systems will need increased control of power flows and volt-age,” favre-perrod says. “this means inter-vening with a current or voltage source. Furthermore, with greater and more difficult

electric loads, the sine wave will look even less like a sine wave, quality will suffer, and there, too, you will need a current or voltage source. power electronic converters can provide solutions, as they are all basically disguised voltage and current sources, although each one has entirely different goals and technical characteristics.” There will also be a need for flexible inter-faces. “all these new distributed energy sources generate Dc or variable ac that will need transformation. new consumers, vehicles and urban transportation systems will need customized plug-and-play inter-faces.” power electronics can also be used

to increase transfer capacity of existing networks—less need for new lines that nobody wants and substations where no space is available—and to interconnect systems. they can provide enhanced coor-dination and ancillary services (including reactive power compensation), helping gain some control over power exchanges and line loading.

power electronics solutionsso, power electronics solutions will take on a whole variety of forms. some of these devices, such as electronic low and medium voltage transformers, are maybe 10 years away. others are currently being developed from technologies already available on transmission systems. D-facts could enhance controllability and increase power transfer capability. static synchronous com-pensators (STATCOMs) could provide wind farms with fast dynamic reactive power support. a european commission-funded project called aDIne, which is focused on active distribution network management, is working on demonstrating STATCOMs in distribution. Medium voltage direct current (MVDC) could regulate the impact of wave or wind generation on potentially weak distribution networks, in addition to providing direct control of real and reactive power flows and helping to maintain system stability. “MVDC and multi-terminal Dc can become pos-sible with voltage source converter (VSC) technology, and such solutions will prob-ably be in operation within five years,” says favre-perrod. for that matter, alstom Grid is currently participating in a collaborative project that aims at demonstrating key features such as protection systems, includ-ing circuit breakers. other applications are already available either in inadequate form—commercially available plug-in vehicle chargers do not yet perform at appropriate levels—or as standalone solutions: storage and distrib-uted generation interfaces; flexible custom-ized interfaces for harbors, factories, airports and data centers; and active filters (AF) to maintain voltage wave form.

A new approach“once you do one of these applications with emerging technology, it

Power electronics converters and transformers will increasingly find their way into distribution networks to control power flows and voltage as a whole range of new applications are introduced. These can include urban transportation systems, but also electric vehicles and new, cleaner heating devices.



becomes easier to do the others, and we may have a platform approach in the future. In the past, each issue was addressed individually, but now we are looking at converters with smart designs that can do several things at a time, so you get more at low incremental cost,” Favre-Perrod explains. For example, the recently completed three-year, e.u.-funded

research project unIfLeX demonstrated a flexible, multifunctional solution, although “cost and performance are not there yet.”the idea is to create versatility, but also scalability. “Now, a 5 MW converter is different from a 50 MW converter and devices are often tailored to specific proj-ects, which means long design times,

unifleX Ac/Ac full converTer uniT

“FACTS are a scalable concept used primarily in transmission systems, but will be needed for distribution in the future,” says Patrick Favre-Perrod. “In distribution, they will fit the same theoretical framework with three categories: series compensation, shunt compensation, and combined.” In series compensation, the power system connects to the

FACTS in series and works as a controllable voltage source, while in shunt compensation, the connection is parallel and works as a controllable current source. The choice of shunt (e.g., D-STATCOM) or series (e.g., SSSC) or a combination (e.g., DVR, UPFC) will depend on grid requirements. “Basically, what you can do with a shunt device such as a static VAR compensator (SVC), you can

also do with a series device such as a thyristor-controlled series reactor (TCSR), but you always opt for lowest cost for best performance.” Series devices are used for power-flow control, stability and oscillation damping while shunt devices work best for power quality, reactive power compensation and voltage support. “And since the world is not black and white, sometimes you need both.”

M o r ePatrick Favre-Perrod

difficult implementation and a lot of test-ing. advances in power e lectronic switches will enable converters that, like Lego toys, can be put together to get twice the output.”other key factors for future grids include interoperability. the quest has begun to simplify connections of, say, renewable generators, with standardized technical solutions and eventually a plug-and-play approach. coordinating actions across the system is also key, so each device knows what to do to contribute to the overall balance. “If you have a small stat-COM that only looks at local signals and adjusts its output accordingly, that is like having one citizen who cannot alone change the president: it will not change the overall situation. But if several devices are coordinated, you multiply the effect, like several citizens voting for a new gov-ernment, and you impact the entire sys-tem. so you need to tell each device what to do.” this can open the way to pools of small distributed generators acting as virtual power plants.clearly, power electronics are at a real turning point, with a whole new philoso-phy and approach. they are poised to play a major role as the need for new applica-tions combines with technical solutions to build a future that is greener and more flexible with respect to distributed energy sources.

Points oF coMParison


fears over looming shortages of petroleum-based oil have focused the industry’s atten-tion on renewable alternatives. the t&D sector has re-discovered the benefits of natural ester oils (those extracted from rape-seed, soya and sunflower). Originally, wind-ings were immersed in vegetable oil before the introduction of petroleum products at the beginning of the 20th century. we are now witnessing an increasing trend in their use in distribution transformers (DT). The big challenge is to extend the use of natural ester oils to high voltage power transform-ers (PT) where electrical and thermal

stresses are much more pronounced. today, only about 100 pt are insulated and cooled by vegetable oil, but research is going strong in order to ensure high reliability in service. “alstom Grid is participating in a whole series of research projects at several european universities,” says christophe perrier, research engineer of the power transformer technology and Innovation center.Natural ester oils have excellent green cre-dentials. with their high flash and fire points, the fire hazard is significantly reduced. they are biodegradable and have low or no toxicity, so spillages have practi-

cally no impact on the environment. In addition, vegetable oils extend the service life of the composite transformer insulation system utilizing oil-impregnated cellulosic materials. “technically speaking, natural ester oils really come into their own with their high water solubility—20 to 30 times higher than that of mineral oil at the ambi-ent temperature, before saturation,” says perrier. as the cellulose-based solid insula-tion is highly hygroscopic, a related advan-tage is that the oil draws moisture out and absorbs it, thus keeping the insulating mate-rial dry and extending its life span.

natural ester oils: a promising solutionnatural esters—commonly called “vegetable oils”—represent a credible option as a “green” insulating liquid in power transformers. They provide definite environmental and safety gains. research, though, continues, as we need to reach the same level of knowledge and understanding as we presently have for mineral oil.

Natural ester oils for transformers—commonly called “vegetable oils”—are extracted mainly from rapeseed (see illustration 1), soya and sunflower. Alstom Grid R&D is increasingly studying different types of natural ester oils such as rapeseed and soya bean oils but also blends of mono and tri ester (see illustration 2). Until now, all Alstom Grid power transformers were filled with natural ester oil based on soya beans such as the Luton 90 MVA, 132 kV transformer installed in the U.K. (see illustration 3).

1

2

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inter-related advantages and drawbackstechnologically, the minimum set of prop-erties to be checked to evaluate any trans-former oil includes dielectric strength, heat transfer efficiency and ageing stability.“Vegetable oils are equivalent to mineral oils under ac voltage conditions, and the dielectric strength of paper impregnated with vegetable oil is broadly the same as that of paper impregnated with mineral oil,” says Perrier. More in-depth investigations are ongoing to determine dielectric strength under lightning impulse conditions, more particularly through the study of electric streamer generation and propagation.Vegetable oils also conduct heat more effec-tively thanks to their higher thermal conductiv-ity. however, they have higher viscosity, which impacts the coolant velocity through the trans-former active part and consequently may affect the overall heat transfer performance. this aspect is effectively controlled by transformer designers through an optimum choice of the oil pumps in the forced oil cooling circuit. one of the biggest technical challenges is to reduce the pour point (the temperature at which the oil does not flow), which is presently a limiting factor for the minimum restart temperature of transformers from

the cold condition. two options are possible, either to act directly on the oil chemistry or to optimize the energizing procedure. the very biodegradability that makes vege-table oils an environmentally attractive pros-pect also influences their ageing stability. It makes them slightly more prone to oxidation, causing them to age faster. nevertheless, this minor issue can be mitigated by the combined action of vegetable oil suppliers and trans-former manufacturers (see sidebar).

A cry for standardswhile there are data and international stan-dards galore for mineral oils, there are as yet no Iec standards addressing the composition or testing of the natural ester oils with their different chemical composition. this lack of standards could be seen as one of the limit-ing factors with regard to the initial rate of implementation of vegetable oils in pt.“Insulating oil in pt is like blood in humans,” says perrier. “It can tell you about the state of their health if you have access to effective means for dissolved gas in oil analysis and diagnostics.” Developing such capability is exactly what the industry is doing, with alstom Grid in the forefront. with such credentials alstom Grid is actively dealing with all environmental challenges.

the case For standards Natural ester oils are fully biodegradable, which makes them more sensitive to oxidation than petroleum-based oils. Vegetable oil suppliers therefore add oxidation inhibitor packages (at low concentrations to remain in a green product classification) and transformer manufacturers propose sealed systems. Even better, Alstom Grid has patented a hermetically sealed design for PT. To date, the difficulty is that no international standards govern additive content and oxidation stability tests for natural esters.Alstom Grid participates actively in IEC and CIGRE working groups (WG) dedicated to the subject of vegetable oils. • IEC TC 14 is developing an international standard as well as oxidation stability tests dedicated to natural ester oil applications. The final draft is expected soon. • CIGRE WG A2-35 is establishing the state of the art of alternative liquids and especially ester oils. The final technical brochure is planned for this year.Meanwhile research teams are running accelerated ageing tests on DT filled with different ester oils. The performance of each oil type is monitored at regular intervals with a view to collecting data for further development.

Christophe PerrierM o r e

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Main Feature chapter II AheAD OF Our TIMe

Wind energy, and in particular offshore wind parks, is the focus of considerable innovation. A key area today is the interconnection of large offshore wind parks through multi-terminal HVDC systems. Another theme is the development of inventive offshore substation design—the self-floating, self-installing platform that accelerates installation and reduces costs. Alstom Grid’s new rail vehicle on-board transformer using secondary windings as an input filter is an innovative technology in another promising market segment.

Innovation and performance



Main Features chapter II ahead of our tIme

the supply of green (environmentally clean), economic (low cost) and reliable power has become a goal. Wind generation, especially in europe, is in the process of becoming a major contributor toward meeting this goal. the european Wind energy association (eWea), a think tank, expects wind power’s share of electricity demand to increase from 4.1 percent in 2008 to between 14 percent and 17 percent in 2020. “this will require the development of new technologies and the introduction of strict europe-wide rules to maximize efficiency, security and reliability,” says dr. Liangzhong Yao, manager of the network solutions and renewable energy technologies department at the alstom Grid research and technology centre in Stafford. Likewise, newly installed wind farms will be called on to provide a range of services to the electricity network, including grid support during and after

network disturbances, frequency response and active power control, as well as voltage and reactive power control.

VSC or LCC?europe has made great strides in develop-ing offshore wind power, which is expected to reach 40 GW by 2020. the grid integra-

tion of large offshore wind farms over dis-tances of tens, some-times hundreds, of kilometers is one of the main challenges facing developers and transmission system operators. almost all offshore wind farms in opera-

tion today are connected to the onshore power systems through undersea hVac transmission cables. due to the high capac-itance of shielded power cables, the length of such ac cables for practical use is limited by the capacitive charging current of the cable. however, this can be overcome by

using hVdc, since there will be no charg-ing current in the dc cables thanks to the constant dc voltage. hVdc technology can be used to transport electricity over long distances or to interconnect different power systems whose grid frequencies are not synchronized.hVdc transmission systems, based on either voltage source converter (VSc) or conventional line commutated converter (LCC) technologies, have been identified as an alternative to hVac connections. they have the advantages of a fully controlled power flow, transmission distance unaf-fected by cable charging currents, fewer

Multi-terminal HVDC system for large offshore

wind park grid integration

Wind power is on the increase, and much of the growth will come from the offshore wind parks now being built and planned. It’s time to invest time and effort in developing an

offshore grid for their connection and interconnection.

Offshore wind power in Europe is expected to reach 40 GW by 2020.

wind power in europe (2009)

Portugal3,535

United Kingdom4,051

Ireland1,260

France4,492

Spain19,149


cables, etc. “While both technologies have been considered for large offshore wind farm grid integration, VSc is superior to Lcc in terms of independent active and reactive power control, fast system control and the fact that there is no need for an external voltage source,” dr. Yao adds.

offshore dC grid connecting an offshore wind farm to one grid is only the first step. Several studies have come to the conclusion that a multi-terminal hVdc (mtdc) transmission system, based on VSc technology, could interconnect a number of large offshore

wind farms, and indeed, connect them to more than one country’s grid. this could deliver significant economic and environ-mental benefits:- Better economical utilization of the grids through shared use- Better power transfer capability- Better security of supply for customers- Better power trading/sharing between various grid entry points or countries—a harmonized approach to capacity allocation and balancing provisions- maximized grid capacities for each time horizon (intraday and day-ahead).Some european countries have huge

Cable solutions For VsC-baseD HVDC sCHeMesOne of the enormous benefits that modern VSC-based HVDC has over LCC is the availability of suitable new extruded cable technologies using a polymeric insulating material (XLPE). Such cables are strong and flexible as well as having a lower cost than their mineral-insulated, mass-impregnated counterparts required for LCC.“XLPE-based cables with VSC HVDC converters provide an economic and much more adaptable technology for both underground and underwater power interconnections than the classic line-commutated HVDC system,” says Roger Critchley, Power Electronics, Strategy & Collaborative Developments Manager at Alstom Grid’s Stafford Research & Technology Centre. “VSC cables enable a practical overland HVDC interconnection system because the cable is lightweight and smaller in diameter, so longer lengths can be accommodated on each cable drum.” Magnetic fields are eliminated and right of way is narrower, making them an ideal solution as inner-city in-feeders. Submarine VSC cables are also available.VSC XLPE cables are available today for ratings up to 1,200 MW at 320 kV.

Roger Critchley M o r e

Denmark3,465

Netherlands2,229

Belgium563

Austria995

Poland725

Hungary201

Lithuania91

Romania14

Greece1,087

Czech Republic192

Bulgaria177

Slovakia3

Sweden1,560

Italy4,850

1. conductor2. conductor screen

3. Insulation4. Insulation screen5. Swelling tape6. metallic sheath7. Inner sheath8. Bedding tape

9. armor10. outer serving

Finland146

Estonia142

Latvia28

Luxembourg35

Germany25,777

Source: EWEA annual report 2009



plans to increase offshore wind gen-eration capacity, especially in the North and Baltic Seas. this could well be a catalyst to develop an offshore grid architecture using the mtdc concept. In particular, it could create the junction of the North, central West and france, u.K. and Ireland regional initia-tives into a single region, possibly with the inclusion of the Baltic initiative at a later stage. this would create an offshore dc grid with transmission lines serving both as inter-connectors and connections for offshore wind farm clusters. one such project is currently under way at the Kriegers flak location in the Baltic Sea between denmark, Sweden and Germany to connect the three offshore wind farms at a newly developed multi-terminal, probably with offshore hVdc back-to-back technology. It has received the support of the european commission. Large wind farms connected in this way by MTDC can potentially provide significant contributions to transmission network oper-ation, e.g., frequency regulation, power

system stabilization, etc. the ability of VSc-based hVdc technology to provide indepen-dent active and reactive power control can be utilized to support the transmission net-work, with resulting technical and economic benefits to the network operators.

overcoming the challenges“to connect large offshore wind farms using mtdc technology will require lots of techni-cal issues and challenges to be overcome,” notes Dr. Yao. For example:- MTDC grid configuration—to identify the most suitable mtdc grid architecture in terms of increasing operation flexibility, avail-ability and reliability, enhancing the control-lability and power transfer capability, and increasing network observability to better exploit and predict system operation stabil-ity limits;- dc circuit breaker for mtdc grid protection. high voltage dc circuit breakers still need to be developed and validated at full scale to operate an mtdc network. they are vital in

case of faults, since the dc circuit breaker must dissipate the energy stored in the cable or line and withstand the system voltage. their task is even more demanding if the ac-dc conversion is performed by VSc. the current rises very rapidly in case of dc short circuits due to the rapid discharge of dc capacitors, so a dc breaker has to break much faster than an ac breaker;- operation and control strategies for mtdc—dc grid voltage control, power shar-ing and dispatch among the connected ac grids, voltage and frequency support of the connected ac grids, etc;- mtdc fault management. alstom Grid, with its considerable expertise in offshore wind parks, has been investing r&d effort on mtdc. “We are focusing on the technical issues in developing cost-effective solutions for new dc circuit break-ers, new VSc hVdc technologies, and coordinated control strategies for normal and abnormal operations of mtdc,” dr. Yao stresses.

Currently existing

Currently planned

Under study

Under study with EWEA recommendation

EWEA recommended grids by 2020

EWEA recommended grids by 2030

eweA'S 20-yeAr offShore network deVeLopMent pLAn

© EWEA


“A substation out at sea has to have a specific functional design. and you need offshore substations because of far distances from shore in order to restrict transmission losses,” says Sven höpfner, design engineer of alstom Grid’s Systems Unit. The question is: what design should that substation have?“this is a very new business,” uwe Gierer, Sales manager Windpower offshore, points out. The first offshore substation—the U.K.’s Barrow offshore wind park—dates back to 2006. With it came issues of harsh operational conditions and weather-dependent access. “We started by learning from the oil and gas industry’s offshore experience.” But in that big, worldwide business, installation cost is less of an issue. “a small wind farm is very cost sensitive. So we had a steep learning curve, reducing installation and service con-straints and time.”

inventing offshore substations for the new wind farm marketas wind farms move offshore, a whole new set of challenges has arisen along with an exciting new market for offshore high voltage substations. today, the industry is inventing solutions for the high seas environment.

The first offshore substationsoffshore substations come in different basic designs. The first is a classic jacket/topside structure, like Barrow, inspired by oil and gas industry rigs. alstom Grid, currently No. 1 in turnkey projects in this field with a 36 percent market share (eight of 22 projects worldwide), engineered, supplied and assembled the elec-trical equipment for the substation platform. Yet, when it was ready for loading, it took days for a suitable weather window to open up. and then there was the corrosion; the sea is, after all, a humid, temperature-swinging, saline environment. alstom Grid’s second project in the u.K.—the robin rigg project—had a design similar to Barrow.the next project was in Germany, where the alpha Ventus platform, another jacket/topside structure, had a patented 110/33 kV 60 mVa oNaN cooled power transformer with a her-

metic design. It required less maintenance, thanks to its specific design and fewer auxil-iary items. Borkum West II, also in Germany, will consist of two 225 mW 33/155 kV power transformers and an innovative seawater cooling system.clearly, though, more adjustments were needed. “It costs a lot to install piles in the seabed and lift heavy platforms for installation using special crane vessels at approximately €1 million a lift. then there is the weather. But the real problem is the whole design approach. the form was already there, and we had to fit the equipment to the deck structure, which is complicated and not very efficient,” says höpfner.

Innovative solutionsas a result, alstom Grid started to develop a full platform concept that reduces

The Alpha Ventus offshore substation on the high seas.



expenditure and risks during construc-tion, installation and operations. the basic idea is that form has to follow function, not the other way around.The solution came as a self-floating, self-installing platform, based on those devel-oped in the oil and gas industry. the alstom Grid offshore platform consists of a sub-structure with cable guides and a large pontoon that contains the transformer and substation equipment, protecting it from the aggressive atmosphere. these are assembled at shore and towed out to sea, where the substructure is lowered. the process reduces the need for offshore vessels (no cranes), has a shorter installation time (jacket and topside in one piece), is envi-ronmentally compatible if suctions cans can be applied (no ramming that could harm marine life), and the foundation can be

completely removed when operation ceases.another system under development combines the advantages of the traditional jacket with a self-floating system. The idea here is to cre-ate a smaller structure that uses less steel, bringing down the price. this solution also resolves a cabling issue. “every offshore sub-station has to pull heavy cables—up to 50 m at up to 100 kg/m (depending on the cable type)—up from the seabed to deck level. this solution pulls them up centrally through an opening in the middle of the platform, rather than up the cable guides mounted at the legs. this makes them easier to handle,” höpfner explains.

The futureWhere are these innovations leading? “at the moment it’s very hard to find a standardized solution,” says höpfner. “the problem is that

each wind farm project is completely different. In the Baltic Sea, there will be problems with ice and snow load, so the structure has to be more solid and at the same time lighter. other projects will have different site-specific condi-tions, needs or cost restrictions. In addition, each customer has its own view of operational requirements for the electrical system design, i.e., level of redundancy, availability and main-tainability.” for now, however, it seems that the big advantage is fully integrated design, provid-ing a turnkey solution, including substruc-ture and installation, with no interface management issues and fewer technical risks. the ultimate in “form follows func-tion.” alstom Grid is well placed to establish this solution as a standard for the many forthcoming projects in the North and Bal-tic Seas.

SeLf-inStALLinG offShore SubStAtion

On arrival at the field, the pontoon is placed in its final position, and the steel tube legs lowered such that the suction cans barely penetrate the seabed.

2After completion of the commissioning test, the three-deck, buoyant pontoon is shipped to its offshore location using only four tug vessels.

1


It’s definitely state of the art, and as of March 2010, Alstom Grid’s new generation of self-floating, self-installing high voltage offshore substation has its first client. Wetfeet Offshore Windenergy GmbH ordered the first turnkey Alstom Offshore Platform (AOP). It will connect the Global Tech 1 wind farm in the German North Sea to an offshore HVDC grid. Global Tech 1 is one of the biggest offshore wind farm projects in Europe so far, with 80x5 MW-class wind turbines in the high seas producing 400 MW. It is located 100 km

from shore at water depths of up to 40 m. Uwe Gierer explains, “Our solution doesn’t need the costly, hard-to-get crane vessels, making it more independent. Installation times are shorter, it is environmentally friendlier than other platforms, and all the transformer’s electro-technical components are inside the platform, which allows cold commissioning onshore and higher security.” The AOP minimizes installation risks with a highly flexible configuration, and opens the way for future offshore substations.

Uwe Gierer M o r e

alstoM GriD oFFsHore platForM Gets tHe Green liGHt

The pontoon, with its working deck, main deck and cable deck, is then lifted to its final height and secured approximately 20 meters above the sea level.

3



optimized multi-system on-board transformers for

tomorrow’s trainsrail transportation is back in fashion, but its future expansion needs equipment that is not only cheaper, lighter and more reliable, but capable of operating across a

multitude of standards and systems. that includes equipment like alstom Grid’s new SWIft on-board transformer.

London to Beijing in two days by train is still but a dream! however, current eco-nomic trends coupled with environmental concerns are giving a boost to rail trans-portation. politicians, business leaders and the public realize the importance of rail as a sustainable means of transportation, and massive investment plans to modernize and expand rail networks are on the drawing board. the market for railroad equipment is therefore promising, and the growth out-look for international corridors will give renewed momentum to this mode of trans-portation. however, it is a complex environment due to the fact that rail networks are historically different from one another. Infrastructure development is very uneven from country

to country, and compared with other modes of transportation, rail depends on a wide range of technologies such as broad gauge or supply voltage. excluding diesel, electric railroad equipment operates through a single technology powered by an external energy supply (mostly via a catenary). Within this single technology, two norms are expected to work side by side, with some systems using ac power supply and some dc—and some both.to respond to this particular situation and move progressively to intermodal railroad vehicles able to operate on different net-works, existing multi-system traction trans-formers must be increasingly adapted to train manufacturers’ and operators’ needs in terms of weight, space constraints and

price. until today, transformer technology was the same for mono- and multi-network operation.

Secondary Windings as Input Filter technologyHalf of the world’s 274,000 km of electrified lines use ac/dc systems, but operators with ac-only national systems are con-cerned too, since they need interoperability when crossing borders—a trend that is likely to accelerate as deregulation opens up mar-kets to international competition.on-board traction transformers are a key element in this, but in a traditional design, there are two active components that are functionally separated and not used simul-taneously: the transformer (AC) and the


reactor (dc filter-ing). alstom Grid’s new SWIft technology (Secondary Windings as Input filter technology) integrates the two to reduce the transformer’s weight, dimen-sions and price. abdelillah el-Brighli, r&d manager on the project, explains: “The aim with SWIFT is to reuse the transformer’s secondary wind-ings as a filtering reactor when shifting from a line with ac to one with dc supply systems. In DC mode, this reconfigured reactor mainly mitigates harmonic currents created by the converters. It is also a reserve of electrical energy for the convert-ers connected downstream in a transitional

s t age , and it fixes a minimal

impedance of the traction machine seen from the overhead line.”although the product itself is new, devel-opment effort could be devoted entirely to the technology, since there are no special materials required within the transformer tank and no additional requirements con-cerning the industrial aspects. this helps keep manufacturing costs down, with

obvious benefits for customers. the project’s technical aims were ambitious though, and included avoiding steep varia-tions in inductance when the dc current is near zero, and having a winding portion

that is short circuited by external switchgear when the transformer is used in dc mode.complete engineering design of the mock-up was completed in octo-ber 2009 and final tests started in march 2010 to validate the calcula-tion methods for induc-

tance as a function of dc current using measurements of self and mutual

Rail networks are historically different from one country to another.


Main Feature chapter II ahead of our tIme

inductance at four stages: a dry test without the magnetic core; with magnetic core but without parallel connection of pri-mary windings; with magnetic core after connecting the primary windings in paral-lel; and with ac+dc superimposed current.the tests validated the technical concept of SWIft and proved that the goals concern-ing weight and size reduction were realistic. even allowing for 200 kg of switching gear,

tHe on-boarD transForMer, a tailor-MaDe proDuCt The on-board traction transformer and inductor sets that are dedicated to equip electric railroad vehicles (AC/DC) are the heaviest components of the rolling stock due to their function: transmission and conversion of the electric energy from the catenary to the traction motors and auxiliary equipment (lighting, air conditioning, etc.). Train control systems subject them to severe harmonic currents, which is why filtering is so important. All-weather operation is vital, too, since the same transformer may be subject to sub-zero temperatures in winter and summer heat waves. This is why all transformers are designed to fit within train constraints in operation and also to be perfectly integrated into the train architecture. As an example, Alstom Grid developed a specific version of France’s TGV Est transformer to set up the 2007 world rail speed record (574.8 kph).

Abdelillah El-BrighliM o r e

SWIft reduces the weight of a 6,800 kg transformer by 430 kg, while at the same time shrinking depth from around 3,750 mm to 3,150 mm.according to el-Brighli, SWIft “reinforces alstom Grid’s reputation for innovative, reliable, cost-effective solutions” in one of the most promising sectors of a market with potential sales of over 1,000 units a year in europe and 1,700 in russia alone.

trAin on-boArd trAnSforMer, before And After

DC Catenary ( 1.5 kVDC or 3.0 kVDC )

DC Input Filter

DC/ACInverters

DC/ACInverters

Transform

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TractionMotors

Traditional Solution SWIFT Solution



DC Input Filter

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DC/ACInverters

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TractionMotors

Traditional Solution SWIFT Solution



Main Feature chapter III maKING eNerGY aVaILaBLe to aLL, todaY aNd tomorroW

Circuit breaker monitoring systems have evolved into high-speed diagnostics thanks to rapid progress in information and communications technology, making them central to asset management. However, information and communications technologies have also given birth to cyber crime so transmission system designers and developers have to be inventive in securing the grid. Rapid progress in electronics, IT and communications protocols continue to make substations increasingly smarter.

Smart products and services


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Main feature chapter III MakIng energy avaIlable to all, today and toMorrow

Monitoring systems: from raw beginners to expert communicatorsFast-moving, web-based Ict

(Integrated circuit technology) and standard communications protocols have enabled circuit-breaker monitoring systems to evolve from basic

monitoring to high-speed diagnostics, opening new perspectives in asset management.

today’s circuit-breaker monitoring systems do more than merely monitor. they assess, analyze, diagnose and dispatch information to users wherever they are. “our team has been working with monitor-ing systems since the early 1990s,” says Jean-pierre dupraz, Innovation department Manager in villeurbanne. “they installed prototypes to monitor FX32d 550 kv circuit breakers in north america.” however, those systems only transmitted raw data with no analysis. In those days, data just went from point to point, and the system’s microcon-trollers were powered by now-ancient 8-bit microprocessor chips.

Improved AvAIlAbIlIty thAnks to monItorInG


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Monitoring systems: from raw beginners to expert communicators“It was a period of building for the future,” says dupraz. “we were learning what cus-tomers needed to monitor: SF6 gas, electri-cal wear and tear, primary contact arcing time and control circuit voltage supply.” Mid-1990, alstom grid was marketing its first circuit-breaker monitoring system, cbwatch1. It was designed to keep an eye on SF6 insulating gas, in response to cus-tomer demand. when the temperature drops, SF6 liquefies, is topped up by a tech-nician, then, when the weather gets warmer, reverts to its gaseous state and expands. this eventually damages con-ventional circuit breakers and causes leak-

age, which can harm the environment. cbwatch1 monitors the leakage rate over weeks, months and years, then computes average figures that it transmits to the manufacturer or regulatory agencies. cbwatch1 was a technical breakthrough, using smart sensors (i.e., sensors with embedded microprocessors and digital com-munication transceivers) to demonstrate that sensitive technology can be used in the harsh environment of switchgear. Sensors were screwed onto dead-tank enclosures and connected to the cbwatch1 with cop-per wires. now, more than 15,000 similar smart sensors are installed world-

Monitoring systems play a critical role in enhancing network availability. Without monitoring and preventive maintenance, the time lag between a fault and its detection and then repair (i.e., unavailability time) can be significant. Preventive maintenance can shorten this time lag; however, with a modern monitoring system, failure detection is instantaneous, and the non-availability period is limited to the repair time. A major plus for network owners and users.

CBWatch2: A great stride in ICT technology.



wide as key components of the sophisticated bwatch3 gIS monitoring system, directly screwed onto gIS enclo-sures and interconnected with copper wires and process bus.

“We all speak the same language”“at the same time we decided to design another product to meet customers’ needs related to operating mechanisms,” dupraz goes on. It was CBWatch2, first marketed in 1999. behind cbwatch2 are great strides in Ict technology that have seen the old 8-bit chips give way to tiny, far more powerful

microprocessors, while wireless communi-cation has multiplied the size, speed and directions of data flow and reduced response times to milliseconds.Perhaps the most significant development came with the release of Iec 61850, a sub-station automation standard for commu-nicating and storing data. these protocols, which can run over tcp/Ip and substation lans, combine with the web to make com-munications the most important function of monitoring systems. “we all speak the same language now,” dupraz sums up.costs have tumbled, too. there are no more software-related expenses or bundles of cop-

Alstom Grid dead tank and live tank circuit breakers can be equipped with CBWatch2 to monitor such parameters as SF6 insulating gas, electrical wear and tear, primary contact arcing time and control circuit voltage supply, and provide network operators with clear malfunction alerts.

The communications capability of monitoring systems is central to asset management.

The CBWatch2 in action.

per wire, as data travels via a single wire or optical cable through the local network—and into the cyber ether. Systems are independent of software platforms, so all users require is a pc and a web browser to check circuit-breaker status wherever they are. they no longer have to go to the substation—the system comes to them! “we use off-the-shelf sensors to make life easier for users,” says thierry Jung, alstom grid high voltage Sen-sors and electronics operational Manager. “no training, no problem interpreting data.”cbwatch1 and cbwatch2 continuously monitor component and condition status, and provide clear, simple malfunction alerts. Maintenance teams can upload additional data or intervene remotely to control the circuit breaker. a newly developed system, SIcU4, also controls some circuit-breaker functions. If, for example, a coil-related problem arises, it will immediately trip.

Asset management diagnostics the communications capability of monitoring systems has made them central to asset management. on deregulated markets where competition is fierce, where high fines are imposed for cuts in power supply and profit-ability is an overriding concern, modern

monitoring systems help make primary equip-ment safer and cheaper to run, and also extend service life. but customers want them to do more. “Increasingly, they want compact digital expert systems that can also perform intel-ligent fault diagnosis and offer operator sup-port,” says Jung. “we have an expert system working for the brazilian utility Furnas cen-trais eletricas”, explains Jung, “we’ve inte-grated a cbwatch2 into an MS2000 power transformer monitor. It’s now monitoring in four more substations.”expert systems work by constantly monitor-ing and processing signals from sensors, then comparing and assessing them against an estimated state according to defined rules. If a conflict arises, it takes action according to a fault scenario.expert systems are the future of monitoring. Jung believes that collaboration with custom-ers can help. “If customers shared monitoring information with us, we could build a whole history and use it to enrich the system’s knowledge base.” but the human factor is an obstacle. “often, people are reluctant to part with their information.” Ironic, given that today’s monitoring systems are such great communicators.

Modular and versatileFirst marketed in 1999, over 1,000 units of CBWatch2 have been sold worldwide for good reason. Designed to standards of expertise that only a proven switchgear manufacturer like Alstom Grid can provide, it is the culmination of 20 years of experience in the field. CBWatch2 is mounted directly on circuit breakers and operates effectively in extreme temperatures.CBWatch2 is a proactive system. It does not wait to be consulted, but constantly monitors a circuit breaker’s condition, alerting users—wherever they may be—as soon as there is a deviation from operating norms. In addition to gas density, it effectively monitors a range of critical operating functions, such as close and open operating times and mechanical wear. It can monitor and spot defects in both hydraulic and spring-operated mechanisms. It is also able to keep tabs on arc duration, primary contact wear, and currents during switching. Other capabilities include monitoring coil continuity and auxiliary supply voltage. While CBWatch2 is capable of doing all of this, it doesn’t necessarily have to—one of its strengths is its modular design, so it can be tailored to monitor only the conditions required by a customer.

Inside a marshaling cubicle.




Cyber security: Virtual threats but real dangers

Many businesses judge cyber attacks a greater threat than theft, terrorism and natural disasters combined. electricity grids are a particularly tempting target.

their complexity means that only a rigorous, holistic approach can meet the challenge.

In 1971, bob thomas wrote an experimental self-replicating program, and computer viruses were born. we’ve come a long way since then. last May, president obama stated: “america’s economic prosperity in the 21st century will depend on cyber secu-rity.” the president also revealed that cyber attacks have already plunged entire cities into darkness, although not in the United States. and according to national security

services, U.S. government agencies are subject to nearly 2 billion attempted attacks a month.private sector networks are under attack in practically every country of the world, too, although for obvious reasons enterprises are not forthcoming about the extent of the problem. that said, according to Symantec, all the 2,100 businesses and government agencies it contacted in 27 countries admit-

ted to cyber losses of some type in 2009.the problem has arisen because criminals and hackers can exploit the very technolo-gies and software that form the core of the numerous systems we now depend on. the web and other computer networks would have remained expensive and limited if they had had to rely on proprietary tech-nologies. the development of cheap, uni-versal cyber systems was made possible

Hackers have proliferated at great speed. Anyone or anything connected to a network is a potential target. None more so than the electricity network. So cyber security is high on the agendas of utilities, suppliers and regulators alike.


NeighboringSCADA Systems

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Firewall Hardened Alstom SystemIDS/IPD

A SECURED CONTROL SYSTEM

by the economies of scale that commercial information technologies such as ethernet, tcp/Ip, and the Internet itself make pos-sible. there is a downside though, as Sha-ron Xia, Security architect at alstom grid, explains. “control systems used to be iso-lated, but now we can link them using standard It infrastructures and protocols, for both critical and non-critical commu-nications. this has numerous advantages

for network design, control and reliability. but at the same time, because the various hardware and software components are well known, cyber attacks are easier too, and they can target a number of installa-tions all using similar equipment.”

Securing the gridthe electricity grid poses some of the hard-est challenges of any network for cyber

defense. take the sheer number of actors involved for a start—just about every room in every building in every town and village in the developed world is linked in. apart from the distributed nature of the network, the complexity of control systems them-selves complicates matters. they may con-tain hundreds of hosts, devices and applications, interconnected via ethernet, modem, wireless, etc., to allow



many types of users to access dif-ferent system components and functional-ities.For Sharon Xia, this means that security cannot be conceived as a kind of barrier that will stop an attack at some point along the line. by then it would be too late. “each component and layer of the network has to be designed with security in mind. our clients need to reduce costs, and part of this means operating in an open, heterogeneous envi-ronment. but it’s often a hostile environment as far as cyber risks are con-cerned, and we have to foresee and forestall these risks at every turn.”Alstom Grid defines secu-rity as ensuring the availability, integrity and confidentiality of energy management, distribution and generation systems, but these are only part of the service. cyber criminals are interested in marketing sys-tems as well, so security has to include these layers too.

Four-step securityalstom grid’s overall approach integrates four different levels of security into the infra-structure.• In a secure network architecture, the net-work is segmented into multiple security zones, each with a specific security policy to ensure perimeter protection (firewalls, IdS/Ipd, etc.) and access control. It pro-vides multiple layers of defense against cyber attacks.• At the host layer, servers and workstations are hardened to minimize the attack surface. access control is enforced to allow autho-rized access only. • Most cyber attacks target the vulnerability

of operating systems and applications, for example, using buffer overflows, SQL Injection and cross-site script, meaning that enhanced application security is a critical component of product quality assur-ance. For the application layer, alstom grid software and firmware offer additional

security features, such as authentication, authori-zation and auditing to help customers meet security standards and regulat ions such as nerc critical Infrastruc-ture protection Standards cIp-002 to cIp-009. • To secure data on the wire, alstom grid soft-ware and firmware sup-port international security standard protocols (SSl,

Iec/ISo/ISa, wS-Security standards) for communicating among alstom grid appli-cations and with third-party applications.In practice, this means that access control, data security, and audit and monitoring functionality must be available in field devices, Ied/plcs, networks and applica-tions. If ease of management was the only criterion, centralized access control would be implemented everywhere. this, however, is difficult when the RTUs and IEDs are located in geographically isolated areas, so local autonomy requirements have to be met, too.attackers’ strategies are evolving all the time, and even the best-designed defense may have vulnerabilities. as Sharon Xia says, “an attacker only has to be lucky once. we have to be on our guard 24/7. that’s why we have a sophisticated, vigilant response capacity bringing together both in-house experts and user groups to iden-tify potential problems and solve them before they can be exploited.”

Defense in Depth The control system of an electricity grid has to allow various types of users to access different system components and functionalities. To do so, it may contain hundreds of hosts, devices and applications, all interconnected via proprietary or, increasingly, commercial technologies such as Ethernet, modem or wireless networks.Many components and software packages were designed at a time when computer viruses were a marginal phenomenon and cyber attacks aimed at crippling a network were unheard of. With the development of smart grids and the need for control system components to communicate among themselves and with other parts of the grid, these legacy components are the weak link in the cyber defense chain. That’s why Alstom Grid is helping clients to modernize their equipment and systems, inspired by a tactic known in military circles as “defense in depth”: building redundant, multi-tiered networks, systematically analyzing potential technical, human or organizational failures, and defining and implementing a series of independent lines of defense to protect against any consequences.

Sharon XiaM O R E

Each component or layer of the network has to be designed with security in mind.


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DATA TRANSMISSION NETWORK NETWORK MONITORING

what power system operator wouldn’t want to be able to scan the system constantly to have real-time, in-depth knowledge of how it is responding, of where its weakest point is, of what needs upgrading next? Such knowledge is more and more critical in a world where grids are working dangerously close to their operational limits, where there is a small margin between actual perfor-mance and peak demand, and where under these circumstances risks of failure are ever-present. recent technological advances are providing solutions that could not have even been imagined 10 to 15 years ago. François gallon, gIS technical director, explains,

“now, we can have real-time control of huge power transmission systems as extensive as those in the United States or europe because we have computational power that is thousands of times higher than it was 10 years ago. operators can now tell what is happening on their systems and on the neighboring systems they are connected to. we can start really building the new smart grids needed to cope with tomorrow’s chal-lenges. It all starts at the substation.”

The key: digital substationsthe substation is a central point in the sys-tem. “If you combine a high rate of informa-

tion about current, voltage and frequency from all a system’s substations, then you can get a true picture of how a system is operating and reacting against distur-bances,” gallon explains. this is possible with modern sensors and other Intelligent electrical devices (Ieds), which can be con-nected together in the so-called digital sub-stations. “It’s like a modern commercial building, where you have a local area net-work to which you can simply connect a telephone, computer, printer, etc.” digital substations use this distributed architecture, connecting various Ieds to a fiber optic network.

new it capability leads the way to smarter substationswith real-time information input from modern sensors and complete interoperability, digital substations will soon be able to meet a whole new set of expectations, thanks to recent progress in electronics and information technology and new communications protocol standards.

TYpiCAL ARChiTECTURE OF A MODERN DiGiTAL SUbSTATiON: pROTECTiON, CONTROL, MEASURiNG AND MONiTORiNG FUNCTiONS


once they are connected, they need to communicate, both within the substation but also with the greater system at large. In the past, there was an abundance of differ-ent protocols, and a lot of effort went into making them all communicate, even though interoperability would clearly be an advan-tage to both users and suppliers. as a result, in 1995, an Iec project group began work-ing on developing the Iec 61850 protocol that set out to cover all substation needs with, for example, the Iec 61850-8-1 for station buses and the more recent Iec 61850-9-2 for process buses. currently, suppliers are working to adopt the latter, as the Iec 61850-8-1 is already well known. It took only a few years from the time it came out before first tenders were requiring it.

what is at stake is to guarantee end users complete interoperability. “once you have interoperability,” gallon says, “it becomes as simple as plug and play, reducing engi-neering and labor costs and giving end users a new degree of freedom. In addition, sup-pliers will have no limits to their creativity and performance when it comes to develop-ing new monitoring and measurement systems.”

Applications and advantagesa lot of work has recently gone into devel-oping all nature of monitoring systems—for gas-insulated switchgear, for power trans-formers, for circuit breakers—so asset managers can get information on the actual operating and aging conditions of any part

What is at stake is to guarantee end

users complete interoperability.

The NXCT-F3 flexible optical current transformer.



of the system. Several current and voltage sensors have been developed and tested in the field, and are currently being or have already been adapted to the latest Iec 61850 requirements. these can be divided into basically three families of application. ncIts are electronic or optical devices to measure current and voltage sources. appli-cation of cIts, or conventional instrument transformers, reuse existing sensors and adapt them to the digital substation, while cb/Sws are another form of Ied that use the same protocols to plug in a circuit-breaker controller and its monitoring of the local area network. alstom grid now plans to deliver a comprehensive range of indus-trial applications.So take high-octane computer power, add

communications protocols, ncIts and advanced condition-monitoring algorithms of primary devices and you get a fully digital substation, which will not only optimize overall lifecycle costs, it will be easier to use. asset managers will have a crucial tool that, with less wiring and fewer commissioning tests, enables preventive maintenance and can extend transformer and switchgear lifetime. these substations will be modular, so they can be tailored to system needs, and open to third-party devices. It will be easy to retrofit protection and controls schemes with minimal outage constraints. Ultimately, operators will have a smarter grid, with bet-ter, more complete real-time situational awareness, making the system more avail-able and secure.

GettinG nCits in the substation

Smarter and smarter substations are combining equipment monitoring, digital control and protection systems as well as NCITs (Non-Conventional Instrument Transformers). All NCIT technologies use electronic terminals with low power outputs and are consequently unable to fit the standard of conventional analog outputs as defined for conventional current and voltage transformers. That is where the new IEC 61850-9-2 process bus standard comes into play. “With progress in digital communications,” says Emmanuelle Catz, System BU Smartgrids and Technical Marketing Manager, “and the new IEC 61850-9-2 standard, we can deal with real-time digital sampled values and so replace conventional sensors with analog outputs by non-conventional sensors with digital outputs.” So, for example, substations can now integrate the NXCT, an Alstom Grid optical current sensor, which brings a new level of accuracy with reduced size and weight so that it fits compact substations and retrofits. Such equipment is easier to implement and performs better than prior solutions, giving operators a constant, remote view of what is happening on the grid.

Emmanuelle CatzM O R E

The NXCM combined metering unit.


Cross-perspeCtives

Three views on protecting and leveraging intellectual property.

The importance of intellectual property

solutions and safeguard that differentia-tion. Patented solutions have an advantage over non-protected ones, which can be copied and marketed by competitors.Patent protection of the company’s major technology solutions is clearly vital—pro-vided it covers its major markets.

What attitude do you recommend in China, a major T&D market?China has a long history of invention and innovation, but a short one in intellectual property. However, Chinese patent protec-tion is now quite exhaustive. The main problem is to get one’s rights respected. Here, China is introducing effective tools, particularly since the innovative Chinese companies themselves are the victims of patent infringement. However, it is still not easy for a European to take advantage of these tools. We recommend taking an aggressive intellectual property position in China and using the services of a European intellectual property specialist with a sound network in China.

“ Carrying out research without

patenting the results means working for the other side! ”

What are the functions and benefits of a patent?A patent is a title deed describing an inven-tion and identifying its inventor and its owner. It enables the owner to prevent others from using the patented invention. It is the only legal weapon enabling its owner to successfully sue a competitor who attempts to use the invention. A patent is also a company asset and a reflection of the company’s technical prowess.

What are the major issues linked to intellectual property? The biggest risk is not to be concerned with intellectual property, meaning others can copy your work and benefit from your research free of charge. Carrying out research without patenting the results means working for the other side! Also, a company with no patents is blocked by the competition’s patents. That means extra effort to find another solution or extra spending on licenses.

A major aim is to differentiate through technological solutions. What role do patents play here?All differentiating solutions developed to respond to user expectations should be patented. The strategy for filing such patents needs to be carefully thought out in the frame-work of the overall strategy for develop-ing the patent portfolio. Issues such as what is the right time and what areas—technological and geographical—should be covered.

“ Patent protection of

the company’s major technology solutions is clearly vital. ”

What are the functions and benefits of a patent?A patent is a key strategic tool. It bestows exclusive ownership of an innovation on its holder and enables the company to protect its market. It also rewards the company’s R&D effort by preserving its technological edge. A patent can also be used to grant licenses to others and there-fore generate income.

What are the major issues linked to intellectual property?A company’s intellectual property policy should focus on R&D awareness of the issues and devising means to identify and protect internal innovation. This structure should have three objectives: protect innovation by trademark or patent, monitor the market for abuses and take the necessary legal action and respect the rights of others.

One company objective is to differentiate through technological solutions; what roles do patents play?That is precisely the purpose of patents—to protect the most innovative technology Frédéric Cogniat

Gérard Poulin


European Patent OfficeDr. Martin Schlaug Patent Examiner

Alstom GridFrédéric Cogniat Director Contracts and Intellectual Property Management

BrevalexGérard Poulin Intellectual Property Consultant and Patent Attorney

What attitude do you recommend in China, a major T&D market?China is changing dramatically in the area of intellectual property. We can now consider its IP system to be similar to that of the European countries. Chinese innovators are filing practically as many patents as Europe and the United States, and legal proceedings against infringe-ment have increased considerably, with remarkable fines. So we should consider China as any other country that is key to our business. We have systematically filed patents there for several years and recently expanded our Chinese intellectual property team.

“A company needs a clear

strategy on which rights to use and where.”

What are the functions and benefits of a patent?Patents have many roles: informative (the patent is published); defensive (to discour-age competitors); cooperative (to promote cross-licensing); aggressive (to sue infring-ers); and financial (as a guarantee for a loan or as a company asset). A company can leverage any or all of these functions when filing a patent.

What are the major issues linked to intellectual property?There are several. For example, the multi-plicity of intellectual property rights such as design patents, copyright, trademarks, etc. Furthermore there are important regional differences. A company needs a clear strat-egy on which rights to use and where. And with special regard to the European markets there is the question of when the long-awaited European Community Patent will come, a unitary patent throughout the Euro-pean Union. This new type of patent could replace the current bundle of nationally enforceable patents and thus lead to a sub-stantial increase in patenting efficiency, combined with significant cost reduction for all parties involved. Dr. Martin Schlaug

Companies endeavor to differentiate through technology. What is the role of patents here?A key use of patents is to build a protective wall around an inventive concept and exclude others from making the same prod-uct or using the same process. Filing a pat-ent can also be used by a company to show potential clients its technical ability.

What attitude do you recommend in China, a major T&D market?The legal basis of the Chinese patent law is almost a copy of the European one. The problem has been one of enforcement, but this is rapidly improving. There is a major project between the European Commission and China, the so-called EU-China Project IPR2, to improve the effectiveness of IPR enforcement in China. Within this project the European Patent Office was selected as the implementing organization. This all means that the main pre-conditions for a secure patent system in China are present and the situation will steadily improve.


ElEctricity lorE

AEG’s SD335 six-system

analog statical distance

protection relay for high voltage grids

(1980).

Today, the uninterrupted supply of electrical energy is taken for granted. Reliability and safety of the electrical energy supply have reached a quality level that is hard to sur-pass, and it is easy to forget how much engineering effort was necessary to get there.In the 1890s, the first bulk-oil circuit breakers and current transformers were introduced, followed by inverse-time over-current protection devices. With the later development of definite-time over-current protection devices, time grading require-ments could be met to a much greater extent. After the First World War, the use of medium voltage systems expanded rap-idly, making a new protection scheme nec-essary.Distance protection for electrical systems developed into one of the most

important elements in protection technology. The associated measured variable is the impedance, which is evaluated by measuring voltage and current values, and a trip time value dependent on this variable. In 1904 the Ferraris disc was introduced as a timer element, followed by an unbiased polarized device that closed its contact when voltage and current values reached a specific ratio. The use of current-carrying thermal elements to determine time periods, where the voltage was instrumental in influencing the timer function, was proposed in 1918 by Dr. P. Meyer AG (later to be acquired by AEG).Distance protection with steady trip time characteristic gradients was achieved in 1922 with the N-Relay, which continued to be developed up to the Second World War

and was as widely used as the AEG distance protection device designed by AEG’s J. Bier-mann, more common with high voltage systems.

Gaining speedAll distance protection devices on the mar-ket up until then still used a steady time characteristic. For such devices the basic time period was 0.5 to 1 s and the trip time 1 to 5 s. Further development and the appli-cation of electromagnetic devices made trip times of less than 0.3 s possible. The “high-speed distance protection device” was born.The trend to reduce tripping times stemmed from the need to avoid power swings and to consider ever-growing short-circuit power levels. In 1937 this led to

A short history of distance protectionThe reliability and safety of electricity supply have improved in leaps and bounds since the creation of the first T&D networks some 120 years ago. This article gives a brief overview of the development of distance protection and the role of Alstom Grid and its ancestor companies.


Stafford relays assembly lines.

ElEctricity lorE


the introduction of metallic rectifiers in protection technology. At the end of the Second World War this development led to bridge-connected rectifier circuits, thanks to which

tripping times of less than 0.1 s were achieved.The development of elec-tromechanical protec-tion devices practically reached perfection for over two decades, and even today they still represent the back-bone of much pro-tection equipment deployed in electri-cal energy systems.

1890s Introduction of the first bulk-oil circuit breakers and current transformers and the development of inverse-time over-current protection devices

1904Introduction of the Ferraris disk

1918• Dr. P. Meyer AG proposes

current-carrying thermal elements

• Creation of the English Electric Company (EE)

1922 The N-Relay is designed

1923Rapid market acceptance of the AEG distance protection device, known as the Biermann’s Distance Relay

1927AEG acquires Dr. P. Meyer AG

1930Production and sales of the N-Relay transferred to AEG

1937Metallic rectifiers in protection technology

1940sBridge-connected rectifier circuits

1950sElectronics gradually introduced in protection devices

1964First-generation static phase comparator

A YTG-relay

1. Fast distance relay SD4M

2. Setting adjustment interface

3. Fast distance relay SD1242.

1.

3.


The advent of integrated circuitsWith electromechanical protection devices reaching their peak, the introduc-tion of electronics in the late 1950s ini-tially made only slow progress. But by the mid 1960s, static electronic compo-nents were introduced, resulting in a significant size and cost reduction. The introduction of integrated circuits in the 1970s represented a quantum leap in protection technology. Introduced in 1980, the Micromho was the first distance protection relay produced at GEC’s Stafford laboratory in the U.K. to incorporate microprocessor technology and uncommitted gate array technology. The Stafford laboratory subsequently devel-oped distance protection devices at roughly

five-year intervals. The Quadramho was designed for phase and ground fault protec-tion of sub-transmission and distribution lines. It is a full-scheme design, which contains two phase comparators together with self-testing logic offering considerable performance and reliability improvements. The Optimho uses multi-processor hard-ware, with microprocessors used in the measuring circuits to produce a direct soft-ware equivalent of the hardware phase comparator used in early generations. The LFZR distance protection relay was then followed by the latest generation of devices, Alstom Grid’s MiCOM. Distance protection, therefore, has long been a tradition at Alstom Grid and a spe-cialty that continues to evolve today.

1968GEC Measurements formed from English Electric, AEI and Chamberlain & Hookam

1980Micromho announced by GEC, the first distance protection relay produced at the Stafford laboratory to incorporate microprocessor technology

1984Release of the Quadramho (GEC)

1985Release of the digital SD 36 (AEG)

1990Optimho announced (GEC)

The Micromho development team

A cArEEr in protEction Dr. Rudolf Simon joined AEG in the Protection Department in 1993. “I’ve been working in the same building ever since—but for several companies: AEG, GEC Alsthom, Alstom, AREVA T&D and now Schneider Electric!” He was soon appointed product manager, the interface between development and the market. “When I started, digital technology was already in use, though we were still using hybrid solutions—analog for measuring circuits, digital for the decision-making processes.” All three major Alstom Grid sites (France, Germany, the U.K.) were working in parallel, and the MiCOM range reflects the regional developments. “There was no uniform distance protection philosophy; different relays incorporated different specs.” GE was U.K./U.S.A. oriented, AEG Central Europe, and France oriented toward Southern Europe. The result is that the range covers all requirements. “The challenge was—and still is—to find the best way for a solution that satisfied everyone. With our different roots, we learned from each other, and worked together like a family. We are still doing it, as we cooperate on the next generation that will merge more of the regional specifics.”

M o r eRudolf Simon

1991Release of the full numerical PD 551 (AEG)

1995The LFZR protection device developed (GEC), EPAC released by Alsthom

1999Alstom brings out the first MiCOM distance protection systems P442 and P437

The Quadramho development team

Free standing Micromho


FurthEr rEAding

Power System Control and Stability (IEEE Press Power Engineering Series) Authors: Paul M. Anderson, A. A. Fouad Publisher: Wiley-IEEE Press; 2nd edition (October 17, 2002)

Power System Commissioning and Maintenance Practice Author: K. HarkerPublisher: Institution of Engineering and Technology (October 31, 1997)

Dielectric Materials for Electrical Engineering

Author: Juan Martinez-VegaPublisher: ISTE Ltd and John Wiley & Sons Inc

(March 11, 2010)

Securing SCADA Systems Author: Ronald L. Krutz

Publisher: Wiley (November 28, 2005)

The following publications will give you more in-depth insight into some of the subjects covered in this issue of Think Grid.

eSCorTS is a work group made up of members from european Union process industries, utilities, manufacturers of control equipment and research institutes. Their mission is to help improve cyber security of control and communications equipment and develop appropriate standards.

The group’s aims are to disseminate best practice on security of SCADA systems, accelerate convergence of SCADA standards, and promote cyber security test facilities. Its work plan covers five main actions:

• Complete a survey of needs for SCADA security

• Identify and evaluate best practice• Stimulate standards convergence• Establish requirements for test

platforms• Disseminate information and advice.

SEE AlSo…

w w w . e S C o r T S p r o j e C T . e U

dAtES For your diAry

30 2421 AuGuSt 30–SEPtEMBER 3, 2010

BrAunSchwEig, gErmAnyISDEIV

Every two years, the ISDEIV brings together scientists from universities, research laboratories and industry to discuss developments in the field of electrical discharges and insulation in vacuum. It is an opportunity for researchers to catch up on recent advances and discuss industry challenges. This year’s agenda covers four main themes: breakdown and flashover, vacuum arcs, applications, as well as surface science and vacuum microelectronics.

12 1417 SEPtEMBER 12–16, 2010

nAnjing, chinACICED 2010

the 4th China International Conference on Electricity Distribution will have the theme “Developing Smarter Distribution.” It will help experts, scholars, engineers and students of electricity distribution explore how to meet the requirements for smart distribution to satisfy growing demand. The event also includes a major exhibition.

OCtOBER 17–19, 2010VAncouVEr, cAnAdACIGRE 2010

CIGRE 2010, organized by CIGRE’s Canadian National Committee, attracts engineers, decision-makers, economists and academics to discuss recent developments. This year’s theme is “Power System Solutions for a Cleaner, Greener World.” the conference will focus on four areas: renewable resources; innovation for efficient power system management; power systems of the future; and the changing role of the power system workforce.

SEPtEMBER 21–25, 2010huSum, gErmAnyHuSuM Wind Energy 2010

Husum Wind is a long-standing major international wind energy trade fair and an important meeting place for industry opinion leaders and decision makers. The congress includes over 60 specialized programs animated by some 150 speakers from all over the world. The 39,000 m2 exhibition will be the meeting point for about 800 exhibitors and 25,000 visitors from 70 countries.

DECEMBER 14–16, 2010orlAndo, uSAPOWER-GEN International 2010

POWER-GEN International is an industry-leading conference and exhibition covering trends, technologies and issues of the power generation sector. More than 1,200 companies from all sectors of the industry exhibit each year attracting over 18,000 attendees. The concurrent sessions look at such topics as industry trends, renewable energy, environmental issues, plant performance issues and others.

OCtOBER 24–28, 2010tAipEi, tAiwAnCEPSI the 18th Conference of the Electric Power Supply Industry and exhibition offers a forum for chief executives, managers and high-ranking officials in all sectors of the power industry. Its theme: “Challenges and opportunities of the electric power industry in an uncertain era.” It includes a series of panel discussions and technical sessions, as well as several technical tours.


hinkgridtSHARINGALSTOM GRIDINNOVATION & PRACTICES

#07

MAin FEAtUrE - 13

Gas-Insulated lInes (GIl) Choices today and tomorrow

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Gib Above Duct

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