Library

Vacuum Switchgear; Past, Present, and Future
2019 ICEPE-ST Kitakyushu, Japan L T Falkingham
Overview:
Introduction, Vacuum Interrupter Technology, A short history of VI and VCB development, The Future

A Study of the arc of a RMF contact geometry at currents below the natural constriction level
2018 ISDEIV Greifwald L T Falkingham, K W Cheng
A study was carried out to investigate vacuum arcs at low currents on Radial Magnetic Field (RMF) contacts used in commercial vacuum interrupter (VI). The RMF contacts operate by moving the naturally constricted arc in a predictable and controlled way in order to have interruption of short circuit currents of 20kA or more. Arcs on RMF contacts at large short circuit currents have been widely studied, but there is a little published about how these contact geometries work at low currents. This is of interest as the vast majority of switching operations for VI are actually carried out at load currents, which are typically less than 3150A rms, and are all below the natural constriction level for the arc. The study was to investigate how these naturally diffuse arcs behave under the magnetic fields induced by the RMF contact geometries.

A measurement of intrinsic outgassing rates in vacuum interrupters
2017 ICEPE Xi An L T Falkingham, R Reeves
Abstract: In our paper The effect of magnetron discharge pressure measurement on the actual pressure in vacuum interrupters (ICEPE TS 2015) it was reported that in 2013 vacuum pressures in the 10-5 mbar range had been measured in a batch of old vacuum interrupters which had been sealed for more than 30 years. This measurement was then repeated in 2015 and found to be in the 10-6 or 10-7 mbar range. It was proposed that the discharge involved in the first measurements had the effect of permanently removing gas from the system to very low levels, and that the pressures seen two years later arose from intrinsic outgassing within the interrupters. Now in 2017 our equipment has been improved to measure low pressures better, and the pressures have been measured again after this additional two-year period.

The Future of Vacuum Switchgear
2017 ICEPE Xi An L T Falkingham
Abstract: The paper looks briefly at the development of vacuum interrupters to date, discusses limitations to the existing technology of Vacuum Switchgear, what these are, and also how these may be overcome. It then moves on to discuss new developments in Vacuum Interrupter/ Vacuum Circuit Breaker technology which are likely to have an impact on the next generation of devices. Finally, it looks forward ten years to what the impact of these developments may be on the use of Vacuum Circuit Breakers, and what switchgear and power systems may look like in the future.

The Future of Vacuum Switchgear – Pushing the Boundaries
2017 XIHARI Workshop L T Falkingham
Workshop Slides: Vacuum switchgear has now been commercially available for more than 50 years. Like most technology Vacuum Interrupters and Circuit Breakers have evolved during that period until we now have an optimised design concept which matches our requirements

The self actuating vacuum interrupter (SAVI)
2016 ISDEIV Suzhou L T Falkingham, W. Molan
Abstract: This paper describes a new approach to the design of Vacuum Interrupters. Presently a Vacuum Interrupter (VI) is a component of electrical switchgear, which relies on an external mechanism to provide the movement of the contacts required for switching operation. The Self Actuating Vacuum Interrupter (SAVI) is a concept whereby the contact movement is performed by means of an internal mechanism within the Vacuum Interrupter.

The return of permanent gas pressure in sealed vacuum interrupters
2016 ISDEIV Suzhou L T Falkingham, R. Reeves
Abstract: The vacuum pressure in Vacuum Interrupters (VI) is usually measured by inducing a magnetron discharge inside them. We have previously reported evidence that if this discharge is continued for long enough in causes the gases to be chemically bonded to solid surfaces in the interrupter, resulting in a permanent reduction of pressure.

The design of a 245kV Vacuum Circuit Breaker
2016 ISDEIV Suzhou L T Falkingham, K. Cheng and W. Molan
Abstract: This paper covers work carried out on the electrical design for a 245kV Vacuum Circuit Breaker, specifically the design of the Vacuum Interrupters. The design is based on a “T” style transmission breaker, with two Vacuum Interrupters in series. The VCB uses a single permanent magnetic actuator with a toggle mechanism to provide the opening and closing forces required and the synchronisation of the two Vacuum interrupters. Vacuum Interrupters are not presently used at these high voltages, but the continuing search for a replacement for the present SF6 based technology for environmental reasons leads us to consider the use of Vacuum Interrupters at ever increasing system voltages.

The effect of magnetron discharge pressure measurement on the actual pressure in vacuum interrupters
2015 ICEPE Busan L T Falkingham, R Reeves
Abstract: Vacuum interrupters (VI) have proved extremely reliable over the past 60 years, but failure can occur, and is most often a consequence of loss of vacuum. If the vacuum pressure rises above a critical level, the dielectric strength of the vacuum collapses, resulting in functional failure of the vacuum interrupter.

Arc control systems for AMF high voltage vacuum interrupters – modelling the contact gap
2014 ISDEIV Mumbai L T Falkingham, W.Molan
Abstract: At present there is a clear trend for vacuum circuit breakers to move up in voltage class from distribution voltages to transmission and sub-transmission voltages.
Developing new vacuum interrupters for these voltages poses a number of challenges, not least the requirement to interrupt large short circuit currents at high voltages. This requires the development of new arc control systems which are effective at the large contact gaps necessary for these high voltages and also have relatively low resistance when closed.

An appraisal of the insulation capability of vacuum interrupters after long periods of service
2013 ICEPE L T Falkingham, R Reeves
Abstract: Vacuum Interrupters (VI) have been the dominant switching device in medium voltage switchgear for the past 30 years. They have proved very reliable and many have been in service well beyond the 20 year service lives that manufacturers assigned to them. We have examined over 200 life-expired VI withdrawn from service for checking. The only end-of-life failure mechanism found was degradation of vacuum. About seven percent had such poor vacuum that they either did not withstand test voltage or they would be expected to fail quite soon. This is a very high rate of failure compared to that reported for VI within their design life of 20 years, and implies that the sample may be showing signs of end of life faults.

Studies in inverse magnetron discharges of vacuum interrupters – part 3 Anomalies
2012 ISDEIV Tomsk L T Falkingham, R Reeves and S Mistry
Abstract: This is the third part of a series of investigations into inverse magnetron discharges in vacuum interrupters. In the previous papers the effect of variations in the magnetic and electric fields were studied. A number of anomalies in the discharge waveforms were seen, including what appeared to be step changes in the characteristics. Different anomalies occurred for single and double magnetron discharges. In this paper we examine the anomalous effects more deeply.

A study of vacuum levels in a sample of long service vacuum interrupters
2012 ISDEIV Tomsk L T Falkingham, R Reeves, C H Gill and S Mistry
Abstract: We report on the inspection and testing of 140 vacuum interrupters that had been in service with utilities. These had significantly exceeded the normal 20 year vacuum lives originally assigned by the manufacturers but were still considered to be good and remained in service. Our sample included interrupters of a number of different types from two manufacturers

The strengths and weaknesses of vacuum circuit breaker technology
2011 ICEPE Xi-An L T Falkingham
Abstract: Vacuum switchgear is today the dominant technology worldwide for Medium Voltages up to 52kV, and is seen as the main candidate to replace SF6 circuit breakers at higher voltages. Vacuum switching technology was introduced into service in the late 1960’s and since that time millions of vacuum circuit breakers have been manufactured. Today it is estimated that over a million vacuum circuit breakers will be manufactured worldwide annually. Vacuum circuit breaker technology now has been in large scale use for more than 40 years and has an enviable reputation for reliability in service. However, amongst the very large numbers in service there are still occasional failures, and historically, particularly in the early days, there have been some problems due mainly to misapplication of the technology both by manufacturers and users.

Studies in Inverse magnetron discharges of vacuum interrupters part 2 – Variations in magnetic field
2010 ISDEIV Braunschweig L T Falkingham, R Reeves, C H Gill and S Mistry
Abstract: This paper reports the second part of a series of experiments to provide detailed information on the characteristics of inverse magnetron discharges in vacuum interrupters. This technique is used widely in the manufacture of commercial vacuum interrupters to determine the level of vacuum and predict the service life. The variation of discharge waveforms with applied magnetic field was examined for both single and double inverse magnetron discharges

Vacuum Interrupters
2009 2nd Conference on Technical Developments in Power Equipment and their Insulation L T Falkingham
A lecture on Vacuum Interrupters given to Xi’an University China

Vacuum Life Assessment of a sample of Long Service Vacuum Interrupters
2009 CIRED Prague, Czech Republic L T Falkingham, R Reeves
Abstract: The electricity distribution industry relies on an ageing population of vacuum interrupters. It is reasonable to ask the question “how long can vacuum interrupters continue to be used?” In order to answer this, the basic principles of a vacuum interrupter and vacuum insulation are outlined, and the difficulty of establishing whether the vacuum will still be good for a further period of use is explained. The shortcomings of the high voltage withstand test which is currently relied on as an indicator of vacuum condition are pointed out. A technique to assess the remaining life of old vacuum interrupters using a vacuum measurement apparatus is briefly described, and results are presented for a typical sample of nine long service interrupters of three types that have been in service for between twenty-five and almost forty years. It was found that some could be certified for another 20 years of use, some for a lesser period, and one should be immediately replaced. It is concluded that revalidation of interrupters in this way is a viable technique and allows their continued use for an extended period.

Studies in Inverse Magnetron Discharges of Vacuum Interrupters:Part 1 – Variations in Electrical Field
2008 ISDEIV Bucharest, Romania L T Falkingham, R Reeves. CH Gill, S Mistry
Abstract: This paper reports part of a series of experiments to provide detailed information on the characteristics of inverse magnetron discharges in vacuum interrupters. This technique is used widely in the manufacture of commercial vacuum interrupters to determine the level of vacuum and predict the service life. The variation of discharge waveforms with applied voltage were examined for both single and double inverse magnetron discharges.

The Use of Vacuum Interruption at Transmission Voltages
2008 IEEE Switchgear Committee L T Falkingham
Presentation to the Fall Meeting of the IEEE Switchgear Committee

Comments on the Paper “Vacuum Interrupters – Sealed for Life”
2007 CIRED Vienna, Austria L T Falkingham
Response to Vacuum Interrupters – Sealed for Life paper by Renz et al

The use of Vacuum Interruption at Transmission Voltages
2007 SWITTRENDS Aurangabad, India    L T Falkingham
An Invited Lecture

The Shieldless Insulation design of Vacuum Interrupters
2006 INSUCON Birmingham, UK     L T Falkingham
Abstract: The design of insulation systems for vacuum interrupters is quite complex due to the combination of demanding electrical and mechanical requirements together with the specific requirements of a vacuum device, and the fact that during the operation of a vacuum interrupter large quantities of metallic vapour are generated which will, unless prevented deposit on the inner surfaces of the insulator degrading its performance unacceptably. Normally this is prevented by incorporating a vapour condensation shield to protect the ceramic.
This paper discusses an alternative, quite radical, approach whereby the insulator itself is specially designed to self protect the internal surfaces, and to tolerate some deposition without compromising its insulation properties. The self protection feature is entirely due to the design of the Alumina ceramic insulator and completely eliminates the need for shields or other protective devices. This ” Shieldless” concept has now been successfully used in vacuum interrupter design for a number of years to withstand voltages up to 45kVrms, and 95kV bil at ratings of up to 31.5kArms. The development of this concept is discussed together with the design of the insulator, and subsequent manufacturing experience

Assessment of Vacuum Insulation condition in Time-Expired Vacuum Interrupters and Switches
2006 INSUCON 2006 Birmingham,UK        L T Falkingham
Abstract: Vacuum switchgear has grown since its first introduction in the late 1960’s to become the dominant switching technology for medium voltage switchgear world wide, with hundreds of thousands of vacuum circuit breakers manufactured every year. However the vacuum interrupters and switches which form the heart of the equipment are sealed for life devices which have a calculated vacuum life of 20 years from seal off regardless of usage. In service the equipment has proven extremely reliable over this period, so reliable in fact that there are many thousands of interrupters still in service which are 30,35, or even 40 years old! This in turn raises a problem. How to verify the integrity of the vacuum insulation within the sealed devices.
The paper discusses this background, together with the excellent experience gained over more than 30 years of field experience, the causes of the rare failures in service, and the effect of ageing, then moves on to discuss the different techniques used in manufacture and in service for assessing the state of the vacuum insulation, together with their advantages and disadvantages. The particular difficulties raised due to the unique properties of vacuum insulation are also discussed, including the Paschen curve and its relation to vacuum condition and life prediction

Vacuum Interrupter Design for HV and VHV Applications
2006 ISDEIV     L T Falkingham
Presently there is an upsurge in interest in the use of vacuum interruption at transmission voltages (< 100kV). This is due mainly to environmental concerns over the use of SF6 gas, which is today the dominant technology for switching applications at these high voltages. Vacuum interruption has dominated the Medium Voltage range of switchgear (<52kV) for many years, and it would appear logical to try to apply vacuum interruption technology to these higher voltage ranges.

Vacuum for HV applications
2006 ISDEIV     L T Falkingham
Thirty Years Service Experience of 132kV Vacuum Circuit breaker
In 1968 four 132kV, 3500MVA vacuum circuit breakers were manufactured by AEI in the UK and commissioned into service by the then Central Electricity Generating Board in the UK. This paper describes the design and history of these revolutionary circuit breakers which are believed to be the first application in the world of vacuum circuit breaker technology for circuit breakers at transmission voltages.

The Use of Vacuum Interruption at Transmission Voltages
2006 IEE International London, England  L T Falkingham
Presentation to 8th IEE International Conference on AC and DC Power Transmission

Environmentally Friendly Design for Electrical Insulation Systems
2005 National Conference on New Technology and Theory of Electrical Engineering, Beijing, China W Qi, S Li, L T Falkingham, M Hassenzadeh, I James
Abstract: As the environment issues become more and more important, electrical equipments must be designed and manufactured to satisfy more strict requirements. It is required that we should consider not only the utility performance but also the environmental performance and corresponding environmental legislations during product design and manufacturing processes. Environmental performance of electrical equipment will be the chief target for the manufacturers to pursue in the near future. In this paper, environmental friendly design for electrical products, especially for an insulation system is presented, including material selection, product design and product recycle. A model of environmentally friendly design for electrical equipments is put forward.

HVDC and Facts for Distribution Systems
2005 Report of WG B4-33 CIGRE Publication 280 K Ericsson, I Iyoda, L T Falkingham et al

Selection Methods of Environmentally Friendly Materials for Power Equipment Based on Fuzzy Performance Summation
2005 China International Energy and Power Conference Beijing, China W Qi, S Li, LT Falkingham, M Hassenzadeh, I James
Abstract: In the past the selection and evaluation of materials were based solely upon the design requirements, but in recent years the environment issues have become more important and it is now necessary to consider their contribution at a much earlier stage in the selection procedure. As there are numerous materials available some methodical means is now necessary to reduce the number to a manageable size. This paper presents a new selection procedure based upon a Fuzzy Performance Summation in order to choose suitable insulating materials for power equipment. A materials selection model is proposed based on the intrinsic character of the properties and their relationship with the design requirements. The data was processed by quantitative analysis and by comparing the numerical values suitable materials chosen.

An Introduction to the design of Vacuum Interrupter Arc Control Systems
2005 Fifth International Conference on Transmission and Distribution Technology Beijing, China L T Falkingham
Abstract: This introduces the concepts and engineering techniques used in the design of vacuum interrupter arc control systems both Axial Magnetic Field (AMF) and Radial Magnetic Field (RMF). The techniques used include electro-magnetic field calculations, finite element modeling and the use of a vacuum demountable chamber to perform high speed film photography of the short circuit arcing performance

The Introduction of Environmentally Friendly Insulation Systems for Medium Voltage Applications
2005 Fifth International Conference on Transmission and Distribution Technology Beijing, China S Li, L T Falkingham, M Hassanzadeh, I James
Abstract: This is the first in a series of articles. It describes the initial methods and techniques used in order to introduce alternative dielectric materials into electrical equipment. A circuit breaker has been used as a demonstrator to define the design performance requirements and develop the procedures of material selection while the environmental characterisation has been performed using an Eco-design tool known as the Environmental Information Management Explorer (EIME) software system. Material selection has been principally based upon their ability to reduce their impact on the environment during their full life cycle and yet maintain both their technical and commercial performance.

The AREVA Emerging Technology Programme
2005 AREVA Tsinghua Electrical Engineering Symposium Beijing, China L T Falkingham
Abstract: This was a presentation of the Areva Emerging Technology Programme which was developed to meet the strategic needs of Areva T&D. The programme was created using a modified form of the DELPHI technology assessment technique and harvested the internal knowledge of the company to predict future trends and the programme needed to meet these needs.

The Assessment of Vacuum Interrupter Condition
2005 Plant Engineers Forum Capenhurst, UK L T Falkingham
Abstract: This presented the basics of Vacuum Interrupter Technology and the methodologies needed to assess the condition of ageing interrupters to DNO utility and industrial plant engineers. It also included a description of the forensic analysis of failed vacuum interrupters and the causes of failure in service.

A Summary of Non-sustained Disruptive Discharges (NSDD) in Vacuum Switchgear
2005 IEEE General Meeting Denver, USA R P Smeets, AGA Lathauers, L T Falkingham, G Montillet
Abstract: This document described the phenomenon, the interpretation and the assessment of Non-Sustained Disruptive Discharges (NSDD). The first approach is to analyze the phenomenon, based on available tests standards and on real testing results. We will look at NSDD in models for capacitance switching, their theoretical relations to over voltages in capacitive circuits, then to tests for certification of equipment. A list of experimental results is given, and a proposal for the assessment of NSDD is suggested

The Evolution of Vacuum Interrupter Arc Control Systems
2005 CIRED Turin, Italy L T Falkingham
Abstract: The paper is intended to give a very basic introduction to vacuum interrupter technology sufficient to allow an understanding of the technology and its strengths and weaknesses, and its current and future evolution. The paper concentrates on arc control and contact materials as these are the key features, which to a great extent determine the performance of the interrupters. The paper is intended to give a very basic introduction to vacuum interrupter technology sufficient to allow an understanding of the technology and its strengths and weaknesses, and its current and future evolution. The paper concentrates on arc control and contact materials as these are the key features, which to a great extent determine the performance of the interrupters.

Fault Current Limiters for Transmission and Distribution Networks
2005 CIRED Turin, Italy R S Parashar, R Banks, L T Falkingham, C Sasse
Abstract: In the liberalised electricity market, with strong emphasis on renewable energy as an increasing part of the generation mix, much of the geographically distributed new generation is more economically fed into local distribution network operators’ (DNO’s) networks rather than the primary transmission grid. Continuing growth in power demand, the use of intelligent/active networks and the addition of distributed generation, (DG) which allows multi-directional power flow, all require tighter interconnections. All of these tend to raise the fault current level of existing networks. Fault Current Limiters (FCL) can help networks to limit this rise, particularly of asymmetrical fault current when X/R ratios are also increased by local addition of generators, transformers or series inductors. A suitably priced reliable FCL that could be introduced into existing power grids without excessively costly network analysis would be welcomed by utilities if it minimised costs of upgrading or reinforcing components to handle fault conditions while allowing increased normal power transmission. The FCL may also become attractive at transmission level voltages, 138 kV and higher.
Maximum expansion of load and DG is expected to be in the medium voltage distribution network. Although FCLs for this market were available over forty years ago they are not normally economically feasible and at present there is, therefore, no established market for such equipment to penetrate. If, however, the cost of purchase, installation, maintenance and losses of this kind of equipment can be offset by savings over the lifetime of other installed equipment then a significant market for a suitably priced and technically acceptable distribution FCL may be quick to develop.

A Summary of Non-Sustained Disruptive Discharges (NSDD) in Vacuum Switchgear
2004 KEMA Symposium on High Power Testing, Arnhem, Holland L T Falkingham
Abstract:

Vacuum Switchgear – An Optimal Solution for MV Applications
2004 SWICON 04 Bombay, India L T Falkingham, S Chakraborty
Abstract: This paper reviews the development and history of vacuum circuit breakers over the past 30 years. Their use in medium voltage applications is covered as well as the technical and commercial advantages of vacuum switchgear when compared with other technologies.

Outdoor Vacuum Switchgear – The State of The Art
2004 IEEE Powercon Singapore L T Falkingham
Abstract: This paper outlines the design of outdoor switchgear, concentrating on vacuum interruption technology. The paper reviews a brief evolution of vacuum switchgear from the 1970’s to the present day, often in conjunction with SF6 as insulation for outdoor use, including applications from 12kV up to 132kV. The historical review is important in order to understand the driving forces and evolution of this type of switchgear up to modern designs.
The paper then goes on to look at the basic design aspects of outdoor vacuum switchgear, and in particular the needs and advantages of vacuum switching technology for this application. As with all technologies vacuum switchgear brings its own character to a design, and this must be taken into account by the switchgear designer.
Specifically switchgear designed for transmission and particularly the distribution of power is examined, as well as a key specialist application for railway use where vacuum switchgear has dominated the application for over twenty years due to its inherent capabilities.– both for traction and trackside use.

Buying R&D from Universities in China, the USA and the UK – an Industrial Perspective
2004 Business – University Research Collaborations Conference L T Falkingham
Abstract:

An Innovative Modern Design of Outdoor Medium Voltage Vacuum Switchgear
2004 IEEE RVP Summer Meeting Accapulco, Mexico L T Falkingham, J Dams, S Ruhland
Abstract: This paper describes a new generation of circuit breakers which take the old dead tank concept and by using the latest vacuum interruption devices and sealing technology brigs the concept up to date as a solution to the outdoor circuit breaker needs for the 21st century. This includes an all welded, sealed for life construction and highly reliable spring mechanism.

A History of fifty years of Vacuum Interrupter Development – The English Connection
2004 IEEE PES Meeting Denver, USA L T Falkingham, G Montillet
Abstract: From the very beginning the UK has significantly contributed to the development of the vacuum interrupter. During the early years of the technology, important techniques and materials were developed which today form the basis of much of modern design. In order to develop viable vacuum interrupters four key technologies are needed. They are discussed in this paper as the“Contact Material”, the “Arc Control”, the “Interrupter Construction”, and the “Interrupter Manufacture”. The description of the 50-year’s contribution of the UK to these four technologies opens the door for a future generation of designers of vacuum circuit breakers.

Basic Vacuum Interrupter Technology
2004 Plant Engineers Forum Capenhurst, UK L T Falkingham
Presentation: a basic introduction to the key technologies used in the design and manufacture of vacuum interrupters. These include special contact materials, arc control geometries, vacuum technology, brazing techniques, clean assembly and vacuum furnacing as well as Electrical Processing, Inspection and Test Techniques (EPIT).

Technology for Outdoor Distribution Switchgear
2004 IEEE CEPSI Conference Shanghai LT Falkingham, XF Braud Chian
Abstract:

The Design of a New Generation of Internal Arc Resistant Switchgear
2004 IEEE CEPSI Conference Shanghai, China Deb, Bailly, Tricot, L T Falkingham
Abstract: Although rare in service, an internal arc fault cannot be ruled out completely, and so manufacturers are now designing equipment to withstand internal arc faults, and to minimise the consequences of an internal fault. The standards for the requirements differ considerably, as for example, the requirements of ANSI are not the same as for IEC. But the standards are continuing to evolve as this issue becomes more understood.
The design of a new range of withdrawable metal-clad cubicle must provide the maximum safety to operating personnel and cope with a number of different demands, including the ability to limit the consequences of a fault to the compartment in which it occurs. These cubicles shall be built with segregated compartments, doors and front covers designed to withstand severe stresses without allowing the effects of the arc to come outside. The paper describes the design of MV switchgear with respect to internal arc, both from an operational and from an operator safety point of view.

Assessment of Non-Sustained Disruptive Discharges (NSDD) in Switchgear, Test Experience and Standardisation Status
2004 CIGRE Paris, France RP Smeets, AGA Lathauers, L T Falkingham
Abstract: Occasionally, interrupters break down relatively long (up to 1s) after the interruption of current and restore insulation immediately thereafter. This event is relatively rare, but tests show that there remains a finite probability of this occurring. Usually, such a “late” breakdown is associated with vacuum switching devices, although (undocumented) observations of self restoring breakdowns in SF6
switchgear have also been reported, indicating that this phenomena may not be restricted to vacuum switching technology only. However this investigation only deals with vacuum based phenomena

An Innovative Design of Indoor Medium Voltage Vacuum Switchgear
2004 IEEE CEPSI Conference Shanghai, China Y Zhang, L T Falkingham
Abstract: The paper briefly describes the design of MV vacuum switchgear which by means of an innovative rotating mechanical system combines the functionality and many of the advantages of both fixed pattern and withdrawable switchgear. The reasons for this approach and the ways for achieving it are discussed. The equipment features the use of the latest design of vacuum interrupters allowing for compact design and the use of an extremely reliable proven low energy spring operating mechanism. The reasons for selecting a spring operated mechanism as opposed to other types of mechanisms are discussed. The design and operation of the circuit breaker unit is described and the design features such as provision of separate compartments and internal arc resistant design leading to improved safety of the equipment, with reduced operational consequences in the event of an internal arc. The design of the vacuum interrupters is also briefly discussed together with the arc control technique used to minimise size and maximise.

The Design and Development of the Shieldless Vacuum Interrupter Concept
2004 XX1st ISDEIV Yalta, Ukraine L T Falkingham
Abstract: This paper briefly discusses the design and development of the shieldless vacuum interrupter concept as conceived by Vacuum Interrupters Limited (VIL) in London in the early 1980’s. The introduction of the shieldless concept was a radical departure from all previous designs and was driven by a change in design philosophy. Previously vacuum interrupter designs were complex and used a complicated multistage manufacturing process. The new design philosophy reduced the manhours required to manufacture a vacuum interrupter by over 50% and reduced the number of components to be assembled (excluding braze material) from 16 to 7. The success of the design is shown by the fact that over a quarter of a million devices have been manufactured to date by GEC (later ALSTOM, then AREVA) plants around the world, and after twenty years the shieldless design is still in manufacture, unchanged.

The New Generation of Internal Arc Resistant Switchgear
2004 IEEE IES/PCA Meeting Chatanooga, USA N Deb, T Tricot, P Bailly, L T Falkingham
Abstract: As an internal arc fault cannot be ruled out completely, manufacturers are designing equipments to withstand internal arc faults. The standards for the requirements differ considerably for example the requirements of ANSI are not the same as for IEC. But the standards are continuing to evolve as this issue becomes more understood.
The design of a new range of withdrawable metal-clad cubicle shall provide the maximum safety to operating personnel and cope up with different demands. These cubicles shall be built with segregated compartments, doors and front covers designed to withstand severe stresses without allowing the effects of the arc to come outside. The paper describes the development with respect to internal arc, both from an operational and and an operator safety point of view.

Outdoor vacuum switchgear the state of the art
2004 Conference paper L T Falkingham
ABSTRACT: This paper outlines the design of outdoor switchgear, concentrating on vacuum interruption technology. The paper reviews a brief evolution of vacuum switchgear from the 1970’s to the present day, often in conjunction with SF6 as insulation for outdoor use, including applications from 12 kV up to 132 kV. The historical review is important in order to understand the driving forces and evolution of this type of switchgear up to modern designs. The paper then goes on to look at the basic design aspects of outdoor vacuum switchgear, and in particular the needs and advantages of vacuum switching technology for this application. As with all technologies vacuum switchgear brings its own character to a design, and this must be taken into account by the switchgear designer. Specifically switchgear designed for transmission and particularly the distribution of power is examined, as well as a key specialist application for railway use where vacuum switchgear has dominated the application for over twenty years due to its inherent capabilities-both for traction and trackside use.

The Return of the True Medium Voltage Dead Tank Circuit Breaker
2003 IEEE T&D Conference Dallas, USA L T Falkingham, A Bieri, XF Braud
Abstract: Over recent years the dead tank concept which was inherited from bulk oil technology has shifted towards dog-house designs. The paper describes the features of a new generation of dead tank circuit breakers based on a design which has been developed using modern technical features such as vacuum interruption, oil free, gas insulation, and a sealed for life concept. The application of these technologies has resulted in a new generation of switchgear which combines the advantages of the old dead tank concept with the benefits of modern technology, bringing the dead tank concept right up to date.

The Next Generation of Vacuum Interrupters using a Design for the Environment Approach
2003 CIRED Barcelona, Spain LT Falkingham, M Schlaug
Abstract: A new range of vacuum interrupters termed « VG » has been developed, optimised not only for technical and cost issues such as the short circuit breaking performance and the size of the devices, but also for environmental impact by reviewing completely the design process and manufacturing technology from an environmental standpoint.
Compared to conventional designs this new ALSTOM technology reduces the energy needed for the manufacturing of vacuum interrupters by 40% and the raw materials (copper, ceramics, etc) by 30%. This technology has already been applied to a new range of vacuum interrupters used in switchgear with service voltages up to 38kV, normal currents up to 3150A and short-circuit currents up to 63kA.

The Return of the True Medium Voltage Dead Tank Circuit Breaker
2003 IEEE T&D Conference Dallas, USA L T Falkingham, A Bieri, XF Braud
Abstract: This paper describes a new generation of circuit breakers which take the old dead tank concept and by using the latest vacuum interruption devices and sealing technology brigs the concept up to date as a solution to the outdoor circuit breaker needs for the 21st century. This includes an all welded, sealed for life construction and highly reliable spring mechanism.

Review of Vacuum Interrupter Development Carried out in London by Vacuum Interrupters LTD
2002 IEE 20th Annual History of Electrical Engineering Weekend Meeting Greenwich, UK L T Falkingham
Abstract: This paper describes the pioneering work carried out in Finchley, London by Vacuum Interrupters Limited. VIL was created in 1968 to pull together the UK expertise in Vacuum switching and over the next 40 years went on to develop much of the critical technology which is used widely throughout the world in modern vacuum interrupters.

Fifty Years of Vacuum Interrupter Development in the UK
2002 XXIth ISDEIV Tours, France L T Falkingham
Abstract: It is only possible to cover fifty years of innovation very briefly, and so this paper will touch upon key developments and ideas generated over this period. Vacuum switching technology was developed originally in the USA in the 1920’s but remained non-viable until the 1950’s, when the support technologies and expertise in vacuum systems, materials technology and clean assembly had become mature and widely available. Serious development of Power Vacuum Interrupters started both in England and the USA in 1953. English Electric and the member companies of what became AEI were involved in the English effort together with the Electrical Research Association (ERA).

Reiview of Vacuum Interrupter Development
2002 IEE 20th Annual History of Electrical Engineering Weekend Meeting L.T.Falkingham
Abstract: Switchgear performs a vital role in the distribution of electrical power acting to control and protect the electrical distribution system. During the past century electrical switchgear has evolved from simple knife switches breaking the hundreds of Amps up to modern circuit breakers capable of interrupting tens of thousands of Amps. Medium voltage switchgear ranges from 1kV up to 38kV, and as the technology has evolved, so the preferred for arcing has changed. Originally this was Air, hut in the 1920’s Oil became dominant and remained so up until the 1970’s when Vacuum appeared. Since then Vacuum has become the technology of choice.

The Four Schools of Thought in R&D Management
2001 Research Technology Magazine – June 2001 L T Falkingham, R Reeves
Abstract: We have found that managers of research subscribe to four different forms of reasoning about the R&D process, which we call Schools of Thought, and we propose that this explains some of the problems that occur in practice. We have also found that publications on R&D management can be classified according to the same four forms of reasoning: however, publications favor one school of thought while managers favor a different one.

Non-Sustained Disruptive Discharges (NSDD) – A new Investigation Method Leading to Increased Understanding of this Phenomenon  2000 XXth ISDEIV Xi’an, China M Schlaug, L T Falkingham
Abstract: NSDD are an intrinsic feature of vacuum circuit breakers and their distinctive properties are due to the excellent ability of a vacuum gap to interrupt high frequency currents. Until recent years they could not be detected during short circuit testing (1) due to their frequency band being beyond that of phenomena associated with standard 50Hz testing. However once discovered their occurrence has been interpreted as a sign of excessive distress of a vacuum interrupter(2).
This paper discusses work carried out to improve the understanding of this phenomenon so that an informed judgment of the real effects of this may be made.

A brief History Showing Trends in Vacuum Switching Technology
1998 XIXth ISDEIV Eindoven, Netherlands L T Falkingham
Abstract: Vacuum Interrupters have been in continuous development since the 1950s, and manufacture since the early 1960s. The paper attempts to identify the trends in the technology over this period by means of a brief overview of work carried out in this field by ALSTHOM and its predecessor companies. The paper concentrates mainly on work carried out in the UK with which the author is fully familiar, having been personally involved in the design and the development of VIs in the UK over the past 20 years. Work by other R&D teams active in this field has been described elsewhere.

Further Experiments in High Current Switching Using Small Contact Gaps
1998 XIXth ISDEIV Eindoven, Netherlands L T Falkingham, K Cheng
Abstract: These tests are a continuation of the earlier series, intended to test hypotheses concerning the results seen.

An Appraisal of R&D Management Research Literature as the Output of a Virtual Organisation
1997 R&D Management Conference ‘Managing R&D in the 21st Century‘ Manchester, UK L T Falkingham, R Reeves
Abstract: We have created a database of information about papers in a body of research publications on R&D management, and used this to examine the structure of research activity in the field.

Context Analysis – A Technique for analysing Research in a Field, Applied to the literature on the Management of R&D at the Section Level
1997 Scientometrics Magazine Vol.42;No 21 L T Falkingham, R Reeves
Abstract: Context analysis is a new method for appraising a body of publications

The Four Schools of Thought in Relation to Research and Development Management
1997 Cranfield Research Working Paper SWP 14.97 Cranfield, UK L T Falkingham, R Reeves
Abstract: We have found that publications in the literature on R&D Management can be classified according to four different forms of reasoning about the R&D process, which we call the schools of thought. We have also found that managers of research subscribe to the same four forms of reasoning. The fact that managers unconsciously think in one of four different ways about R&D management explains some of the problems that occur in practice. A preponderance of publications favor one school of thought, whereas a preponderance of practical managers favor a different one. This raises a doubt about the degree to which the published papers meet practitioners’ perceived needs.

Context Analysis – A Technique for Analysing Research in a Field
1997 Cranfield Research Working Paper SWP 11/97 Cranfield, UK L T Falkingham, R Reeves
Abstract: Context analysis is a new method of appraising a body of publications. The process consists of creating a database of attributes assigned to each paper by the reviewer and then looking for interesting relationships in the data. Assigning the attributes requires an understanding of the subject matter of the papers. We present findings about one particular research field, Management of R&D at the Section Level. Our findings support the view that this body of academic publications does not meet the needs of practitioner R&D managers. The paper discusses practical aspects of how to apply the method in other fields.

Experiments in High Current Switching Using Small Contact Gaps
1996 XVIIth ISDEIV Berkley, USA L T Falkingham, K Cheng
Abstract: A series of tests were performed on two types of commercial vacuum interrupters, herein called Type A and Type B, to ascertain the effect of the contact gap on their high current interruption ability. The tests wee carried out on a synthetic test plant at 12kV; 31.5 kA foe the type A and 12kV;a3.1kA for the type B, all values are rms. Three interrupters of each type were tested at contact gaps between 8mm and 1mm. In addition, identical contacts were subjected to short circuit testing in a vacuum demountable chamber which allowed filming to the arc by means of a high-speed camera. The results indicate that one type, Type A, showed a significant reduction in the probability of interruption of the rated short circuit current at contact gaps between 4mm, whereas the other type, Type B showed no degradation at contact gaps down to 1 mm. The reasons for this are discussed

An Appraisal of the R&D Management Research Literature as the Output of a Virtual Organisation
1996 IEMC’96‘ Vancouver, Canada L T Falkingham, R Reeves
Abstract: We have created a database of information about papers in a body of research publications on R&D Management and used this to examine the structure of research activity in the field. We found that different types of author tended to produce papers with different types of outcomes and also that different authors appeared to subscribe to different schools of thought about the R&D management process. Researchers generally subscribed to different schools of thought from researching practitioners, which raises a question about the utility of this body of research for those who might be thought to be its intended beneficiaries.

Trends in Vacuum Switching Technology
1994 Proceedings of the 4th I.E.E. International Conference on Trends in Distribution Switchgear London, UK L T Falkingham, GJ Rushton
Abstract: Vacuum switching technology has seen continuous progress since the first commercial vacuum switches were produced during the 1950’s and 1960’s. From the very beginning GEC ALSTHOM and its predecessors have made significant contributions to the development of the technology, both with regard to vacuum switches and vacuum interrupters. This article reviews this evolution to date with examples from the Company, and describes recent work carried out suggesting scope for significant future developments.

The Creation of a High Technology Facility in India
1993 Indo-British Partnership Initiative Conference Bombay, India L T Falkingham
Abstract: This paper describes the setting up of the GEC Vacuum interrupter manufacturing plant at Salt Lake, Calcutta. The vacuum interrupter plant is a state of the art facility manufacturing both traditional VIL vacuum interrupters and also the very latest shieldless designs. This facility shows the commitment of GEC to provide state of the art technology into India.

The Design of High Power Vacuum Interrupters Without the Use of Metal Vapour Deposition Shields or Voltage Grading Shields
1990 XIVth ISDEIV Sante Fe, USA L T Falkingham
Abstract: A study was performed to investigate the role of metal vapour deposition shields in high power vacuum interrupters. The original study led to the concept of building devices without including metal vapour deposition shields or voltage grading shields. This was investigated and successfully carried out by means of specially shaped Alumina ceramic insulators which were designed to protect the sections of their surfaces from the effects of metal deposition which otherwise would have led to significant degradation of the voltage withstand capabilities of the insulators.

Vacuum Interrupters South Africa – The Introduction of a New Technology
1989 Invited Lecture/Paper SAIEE Cape Town, South Africa L T Falkingham
(Won the 1989 Best Paper Award of SAIEE)
Abstract:

Vacuum Interrupter Manufacture in South Africa
1989 Elektron – Journal of the SAIEE May 1989 Vol:6;No.5 L T Falkingham
Abstract:

Advances in Vacuum Interrupter Design
1986 2nd I.E.E. International Conference on Developments in Distribution Switchgear London, UK L T Falkingham
Abstract: Arcs in vacuum have been widely studied and the physical principles of operation of vacuum interruption established. However, the optimisation of the performance of commercial interrupters requires a study of practical interrupter contacts operating under service conditions.

Recent Advances in Vacuum Interrupter Design
1986 CIGRE Paris, France L T Falkingham
Abstract: The paper describes the development of new interrupters performed using a demountable vacuum chamber designed so that they can be photographed using a high speed cine camera.

The Development of a new Generation of Vacuum Interrupters
1985 GEC Review London,UK L T Falkingham
Abstract:

Recent Progress in Vacuum Interrupters
 1984 Proceedings of the 2nd GEC T&D Seminar L T Falkingham, P Malkin
Abstract: In previous papers on this subject the programme for vacuum interrupter development was outlined. In this paper we are now able to report on the success of this work which will results in a complete range of interrupters covering 16 types and 3 frame sizes. We are now in a position to predict with confidence that the new range will restore VIL’s position as a market leader in this technology.

Developments in Manufacture of Vacuum Switches
1984 GEC Journal for Industry Vol:8;No.3 A Turnbull, G Rushton
Abstract: In 1980, to maintain its world lead in vacuum switch technology, GEC Vacuum Equipment Limited began a new development programme , leading to the manufacture of the first of a new range of ceramic enveloped vacuum switches, which feature metalised ceramic envelopes and new style contacts….