1verygood7c2 paper 3 - proposed electric traction for auckland 29 october

IRSE Technical Meeting: Auckland of 9 7th November 2008

PROPOSED ELECTRIC TRACTION SYSTEM FOR AUCKLAND

Jan Stelmach

MSc Elect Eng CPEng MIEAust

D’ACE Design And Consulting Engineers

SUMMARY

The electrification of the Auckland passenger service is one of the biggest transport infrastructure projects undertaken by the government of New Zealand.

The Auckland Electrified Area (AEA) consists of approximately 175 Single Track Kilometres over five existing, yet to be built and upgraded railway lines.

This paper describes the general requirement for the railway fixed electrical infrastructure and then discusses the applied process and tools used to determine the most appropriate traction system for the Auckland electrification. It also points to the challenges encountered and solutions found during that process.

The project is in progress and therefore this paper refers to its present status as at the end of September 2008.

Figure 1, Map of Auckland Railway Network

1. INTRODUCTION

The long awaited electrification of the passenger service railway in Auckland will extend from Swanson in the West, Papakura in the South and to Britomart in the CBD. The Eastern line from Westfield as well as branch lines from Onehunga and Manukau will also be electrified. This work is in progress.

Electric power will be supplied from railway substations located in Penrose and Southdown.

The presently considered traction infrastructure is a Simple Rail Return 25kV 50Hz Overhead Wiring system.

There are still several unknown factors that may impact on the final details of the selected system from the type of signalling system to be used to the electrical characteristics of the rollingstock.

Jan Stelmach Proposed Traction System For Auckland D’ACE Design And Consulting Engineers


2. TRACTION POWER SYSTEMS IN THE WORLD

There has been a significant revival in railways in general and electrified railways in particular all over the world in the recent past. This phenomenon can be attributed to increasing population levels, environmental concerns in respect to CO2 emissions and high oil prices. The comfort of rail travel also contributes to the increased popularity of this form of transport.

Electric railways have been the backbone of transportation systems in Europe for decades. Examples of recent major projects in Asia include Kuala Lumpur in Malaysia and Perth and Brisbane in Australia. This year the government of South Australia allocated funds for the electrification of the Adelaide metropolitan passenger system of some 200 Single Track Kilometres.

The function of electric railways is to safely move people and cargo using electric trains that travel, under their own power, on electrified tracks. The ‘electrified tracks’ are termed electric traction system.

There are several types of electric traction systems ranging from low voltage to high voltage, direct current and alternating current, overhead and third or fourth ‘live’ rail i.e. current is collected from rail mounted at track level. European railways use both ac and dc high voltage overhead systems on intercity main-line services whilst inner city mass transit (operating trams, underground lines and trolleybuses) are usually powered by a dc low voltage network.

To set the scene for discussion on the topic of this paper (i.e. selection of Traction System for Auckland) it is worth going into some further details of examples of electric railway networks in Europe and Australia.

Countries that form the European Union, for historical reasons, developed and now maintain electric traction systems width widely different characteristics. This situation is similar to Australia’s rail networks in respect to rail gauges. Separate colonies established gauges based on individual preferences and often, country of origin of their respective chief engineers. Now, in federation, states have to deal with the issue of compatibility of rolling stock and maintain dual and even triple gauge rail tracks to accommodate multiple rail gauges.

System Voltage Long Distance Traction Lines

1.5kV dc 11%

3kV dc 38%

15kV 16.7Hz 18%

25kV 50Hz 33%

Table 1, Traction Lines in the World, 19971

1 Data from ‘Contact Lines for Electric Railways’ Siemens

Publication 2001

Germany, one of the most populated and industrialised countries in Europe operates a15kV a.c. 16.7Hz network. The power supply comes from Deutsche Bahn’s own generation and distribution 110kV single phase system that is separate from the rest of the country’s transmission network. The 110kV is transformed to 15kV at railway substations.

Figure 2, 15kV ac ICE Train on purpose built high speed

track, Germany

Neighbouring Poland adopted in the early 1900’s a 3kV d.c. system. It seemed an excellent idea at that time. The speed and torque of d.c. motors have been, until the recent development of power electronics, relatively easier to control than induction motors. Obviously the use of lower voltages to feed railway network has the disadvantage of a high current required to provide the same power to the trains and this in turn causes a significant voltage drop along the line. To counter this a much larger number of substations needs to be built. 100 years on and real estate is at a premium in Europe. Going further west, the traction system in the United Kingdom is 25kV a.c. 50Hz overhead whilst southern France runs their trains on a 1.5kV d.c. network. Despite all of these technical and political differences, the trains run smoothly between European countries.

Figure 3, 600Vdc Tram in Warsaw, Poland



Member countries of the EU put a lot of effort into inter-operability of their trans-European high-speed rail systems. This has manifested itself in the appointment of the European Association for Railway Interoperability in 2002. The Association is responsible for preparing and issuing technical specifications for the interoperability of each system. Specifications concern design, construction, upgrading and operation of the fixed infrastructure and the rollingstock.

The importance is also signified by the development in late 1990’s and early 2000’s of several standards to regulate in great detail all technical aspects of railway networks across Europe.

Lowest Non-

permanent Voltage

Lowest Permanent

Voltage

Nominal Voltage

Highest

Permanent Voltage

Highest

Non-permanent

Voltage

Electrification System

[V] [V] [V] [V] [V]

Direct Current

(mean value)

400

500

1000

2000

600

750

1500

3000

720

900

1800

3600

770

960

1950

3900

Alternating Current

(rms value)

11000

17500

12000

19000

15000

25000

17200

27500

18000

29000

Table 2, European Voltage Systems2

Another interesting example is the German city of Karlsruhe that has, as a first in Europe, implemented track-sharing for light and heavy rail vehicles using dual Voltage (15kVa.c. and 750Vd.c.) rollingstock.

Development of power electronics technology and its proven applications became the main reason for selecting 25kV ac 50Hz as the preferred traction system in countries that relatively recently commenced electrification.

The examples in Australia are the Brisbane passenger and Queensland freight network operating at 25kV and 2x25kV (Autotransformer) respectively (electrified in 1970’s) and Perth with its 25kV Booster Transformer Return Current system where the first lines were electrified in the late 1980’s.

ONTRACK owns and operates the North Island Main Trunk using a 25kV autotransformer system in the section between Palmerston North and Hamilton. This section of line was electrified in the 1980’s

3.

The clear advantages of a high voltage a.c. system are lower line currents that translate into better voltage regulation along the line, lesser number of substations to service similar lengths of the track in comparison to d.c., smaller cross sectional area of overhead conductors, longer

2 EN 50163:1995

3 ‘NIMT Railway Traction Power Supply System’ M. Denley,

IPENZ Paper, Dunedin, NZ, Feb 1989

distances between supports that in turn improves aesthetics of the installation.

Figure 4, Karlsruhe Tram sharing DB Main Line

3. ELECTRIFIED RAILWAYS

When asked what is an electrified railway, answers usually differ as widely as the engineering speciality of responding professionals. One would however have to agree that an electrified railway is a complete system. This is a system that consists of several components, all of which need to work seamlessly together to provide the required service. By the service, we mean the infrastructure that allows passengers to travel in comfort or move cargo on time in a reliable and safe way. As the specification of the required service is in the domain of planners and operators, this paper will focus on issues relating to electrical infrastructure which supports that service.

Figure 5, 132/25kV Railway Substation, Perth, Australia

Our main interest is the electric railway fixed infrastructure. In broad terms, it consists of power generation, power supply, power distribution and an overhead wiring system that, through the pantograph to contact wire contact point, provides power to electric trains. Generation, although an important part of the infrastructure, will not be discussed further as most of the railway operators source power from public networks and therefore this is normally outside their control. All components of fixed infrastructure are shown in Figure 5. Other subsystems like protection, communication, traction SCADA as well as earthing and bonding



are hidden from the view but they play an essential part in supporting the safe and reliable operation of the electrical infrastructure. 3.1 Power Supply Power supply to railway substations is sourced from public High Voltage networks. Due to high variations in magnitude of the single phase electrical load, the power source must have high level of short circuit power capacity. In Perth, these values are in an order of 5 to 6GVA. Typically networks at 132kV and above are considered to be suitable as power sources. Additionally, the preference is given to connections at major terminals rather than radially fed zone substations due to the much higher reliability of ring connected nodes. The higher the incoming voltage and short circuit power however the higher are the costs of the step-down railway power transformers due to increased cost in insulation. The usual challenge is in finding a suitable power source especially in less industrialised and remote areas. 3.2 Power Quality Considerations The single phase load presented by electric rollingstock causes voltage and current imbalance, voltage fluctuations, emits harmonics and in the case of older style rollingstock propulsion systems (6 and 12 pulse converters), has low power factor. In short, electric railways are classified as highly fluctuating and distorting loads. The local transmission network providers quarantine their networks by requiring customers to meet certain load performance criteria. The criteria (also referred to as performance standards), are mainly based on the AS/NZS 61000 suite of standards regarding Electromagnetic Compatibility, setting and assessing allowable levels of flicker, harmonic emission limits, voltage imbalance and power factor at each point of connection to the network. A typical harmonic spectrum at point of connection, without any applied compensation, is shown in Figure 6. Application of active filters, Static VAr Compensators or Phase Balancers is needed to bring the values within the required performance standards. Installations are expensive and due to the fact that the load at each connection point needs to be assessed and designed individually, installations may take up to 2 years to complete. 3.3 Power Distribution Once power is brought to the railway substation it is transformed to the levels at which the rollingstock operates and distributed to sections of the electrified lines. Distribution is done at feeder stations and track sectioning cabins (TSC) for better control of voltage levels, current in each

feeder and protection i.e. to isolate faulty sections whilst allowing remaining sections to operate. Feeder stations and TSCs utilise indoor type circuit breakers contained within suitably IP rated enclosures. The preference is to locate enclosures within a railway reserve for a number of reasons, one of them being the required separation of traction and other earthing systems. The protection scheme for 25kV railways consists of differential protection across transformers and incoming cables, distance protection for individual feeder lines and overcurrent protection as a back up for transformers and feeders. Modern relays, also known as Intelligent Electronic Devices (IEDs), offer an excellent fault locating facility that enables maintenance crews to be directly dispatched to fault locations to undertake corrective works. Recent experience in Perth shows that faults can be located with +/-100m or even better accuracy. A complex interlocking and control system is in use. It allows for remote switching, monitoring and prevents setting of incorrect feeding configurations e.g. paralleling of transformers.

Figure 6, Voltage Harmonic Spectrum, Summers St

Substation, Perth, Australia4

3.4 Overhead Wiring System The overhead wiring system is an overhead power line in which the conductors are supported by structures over the railway track. The contact wire from which the train’s pantograph collects electric current is suspended off the messenger (catenary) wire by droppers. Both are auto-tensioned to compensate for temperature variation. Other aerial conductors are Return Current conductors in RC systems and the Earth Wire. In the case of ac railways, three basic overhead traction systems are commonly used. They are Simple Rail Return Current, Booster Transformer Return Current and Autotransformer systems. Selection of the overhead system has a fundamental impact on the feeding configuration and components of power supply and distribution systems. Several factors determine which system

4 Public Transport Authority, Perth, Australia, Power Quality

Report, 2007



shall be used as each has its own advantages and applications. Considerations are usually in two categories i.e objective and subjective criteria. Demand for electrical power, length and number of lines, availability of suitable power supply points in the proximity of the railway, layout of network, levels of Earth Potential Rise within the railway corridor, levels of induced voltages, clearances, extent of civil works required and naturally cost belong to the first category. A decision on selection of a system would appear to be a simple exercise: pick a system that meets the minimum performance standards for the lowest possible cost within the time given to complete the project. The performance standards as well as costs can be calculated, measured or simulated by well established tools available to the engineering profession. However, engineers have, very often, to leave their comfort zone and consider other, the less objective, criteria. These are political pressures, compatibility with existing infrastructure, impact on future works that are well beyond the planning horizon, familiarity with a particular system, previous experience and sometimes, simply the preference of individuals making the decision. In the end the selection of a system is the result of all these considerations. If every criterion could be represented as a vector in Euclidean space then the result would be a vectorial sum using engineering terms.

Figure 7, Return Current in AT System

Figure 8, Return Current in BTRC System

Figure 9 Return Current in Simple Rail Return System

The Simple Rail Return system consists of contact and messenger wires and earth wire. The traction current is returned to the feeding transformer via rails. A significant portion of return current however enters the soil due to the rail to ground leakage. This system offers the greatest simplicity in construction, low line impedance and the lowest construction cost of the line. The disadvantage is a

higher level of induced voltages on services parallel to the track. The Booster Transformer Return Conductor system collects the return current from the rails by means of in line installed booster transformers, thus to certain degree preventing the current entering the soil. These are current transformers of 1:1 ratio with the primary winding connected in series with contact line whilst secondary is connected in series with a dedicated Return Current (RC) conductor. The RC is connected to rail at the mid point between BTs. The line current in BT forces the ‘extraction’ of return current from rails and its return to feeding transformer via RC conductor. Typically, the BTs are installed at 3-3.5km intervals. The disadvantage of this system is much higher line impedance, in comparison to simple system due to the presence of BTs and RC conductors in the return path, adversely affecting voltage profile that in turn restricts permitted lengths of feeding sections. Another disadvantage is the requirement for connecting BTs across Insulated Overlaps impacting overhead design. The advantages are relatively good screening and low overall system encumbrance.

Figure 10, Pantograph - Contact Wire, Perth, Australia

The Auto Transformer (AT) system is characterised by a 25kV energised return circuit known as negative or auxiliary feeder or auto feeder in NZ. Both contact line and negative feeder are at 25kV in respect to the traction earth [with 180deg (electrical) shift between them]. The advantage is much longer feeding sections and good screening. The disadvantages are the high cost of double pole switchgear, cost of centre tap transformers, need for land to place relatively large autotransformer installations and the high cost of civil works to accommodate high system encumbrance. The AT system is predominantly used on the high speed, intercity lines, outside urban areas. The performance of current collection between the moving pantograph carbon strip and the underside of the stationary solid contact wire is most critical



to the successful operation of the electrified railway. The higher the speed the more important the adherence to design principles and quality of installation become. Operating speed up to 160km per hour is considered as low. Several proprietary systems have been developed and are in service in the world. Both Perth and Queensland use the 25kV a.c. OHWS that is based on the British Balfour Beatty Mk3 design, modified to suit local conditions. The Ausbreck low speed pantographs put in service in Perth perform satisfactorily. 3.5 Earthing and Bonding The earthing and bonding of electric railways, the ‘black magic’ of electrical engineering, deserves special attention as its performance has a direct impact on the safety of passengers, railway workers, and the general public. The electrical system on a.c. railways is in fact similar to an earth return system. The flow of electrical current causes Earth Potential Rise within railway corridor and induces current and voltages in services that are parallel to the railway track under both normal and short circuit (fault) conditions. These services are both railway owned and belonging to third parties. Obvious examples of railway services are signals, communications circuits and LV power supplies whilst third parties’ are pipelines, telecommunication circuits and power circuits not associated with railway. There are two ways of dealing with the EPR issue, either by bonding or separation. A reduction in induced voltage is usually achieved by screening, or where this is not practical, by relocation, installation of insulated sections, or replacement with services made out of non-conductive materials. The allowable limits are regulated by several industry relevant standards. The EPR limits, adopted by Perth and Queensland, within railway reserve are limited to 60V under normal operating conditions and 430V (670V with one critical bond removed) under fault conditions. European railways follow time duration dependent limits, also termed as permissible touch voltages, specified in European standard EN 50122-1. To compare these two approaches, in accordance with the above standard, the minimum time required to open a short circuit at a touch voltage level of 670V is 200ms. Modern relays and vacuum circuit breakers can break the circuit under 150ms. Railway organisations put significant effort into regulating (by sets of rules) the earthing and bonding of their own and adjoining infrastructure, undertaking comprehensive simulations of normal and fault conditions and detailed inspections before lines are energised. Very often, before commencement of services, the completed installations undergo EPR tests under normal and

controlled fault (short circuit) conditions to ensure that measured touch potential values are below allowable limits. 3.5 Traction SCADA The Traction Supervisory Control And Data Acquisition system assists in fast responses to disturbances in the network, in undertaking safe and timely planned isolations and restoration of power and monitors the performance of the system.

4. AUCKLAND ELECTRIFIED AREA The decision by the New Zealand government to electrify passenger railway network in Auckland prompted one obvious question: what system should be used?

ONTRACK had in the past commissioned several studies and reports in justification of the proposed electrification. Produced documents discussed a number of solutions that would satisfy the service requirements and could be delivered within the time and budget allocated to the project. However the only objective method to select an appropriate traction system, is to test the network performance by applying comprehensive and proven simulation software. In June this year, ONTRACK awarded a contract to Siemens to undertake a power study.

4.1 Power Study

The main aim of the power study was to assist in the selection of the traction system that would meet the planned service levels. To do so the performance of the entire electrified network under various conditions had to be simulated. The input required consisted of track data complete with grades and curves, location of stations, time table and train consists, dwelling times at stations, passenger loading, electrical feeding and sectioning configurations, rollingstock mechanical and electrical characteristics, transformer characteristics, power source impedance, length of feeder cables from feeder stations and track sectioning cabins, overhead wiring system configuration as well as type of conductors to calculate line impedance.

Several criteria are set to assess the performance of the system, leading to the ultimate one, that is its ability to meet the required service. These criteria allow for a detailed assessment of the network’s performance. The criteria for voltage limits, based on EN50163:2004 are summarised in Table 3.

Other criteria include transformer capacity, values of electric current in feeders, Earth Potential Rise (EPR) levels and power quality parameters.

It is well understood that an outcome of any software based simulation is only as valid as the accuracy of the input data. In the case of



Auckland’s electrification several assumptions had to be made. Assumptions were necessary for yet non-determined factors like rollingstock characteristics including assumed regenerative braking capability, exact OHWS configuration, time table and train consists and lengths of feeder cables. Assumptions were made based on experience gained on similar projects in the past attempting to be on the conservative side. This approach was taken further by undertaking sensitivity analysis in the form of increasing line impedance by 10%.

Table 3, Voltage Limits

All three traction systems, as described earlier, were tested. The simple rail returned system showed encouraging results. Outcomes of the simulations showed that voltage levels at the electrical extremities of the network, capacity of transformers and currents each feeder will be well within the limits. The simple rail return system has been selected, subject to a number of other assessments still in progress, as the preferred traction system for the Auckland Electrified Area.

Another goal of the power study was to assess the safety of passengers and railway workers in relation to Earth Potential Rise. Part of this voltage, referred to as a touch potential, is the electric voltage that may appear on human body, when bridging, hand to foot, a conductive component of the system, normally at earth potential (e.g. train, mast, structure), under fault conditions. Also, an accessible voltage, the voltage that can be bridged by a person, under normal running conditions was simulated. One of the factors affecting EPR is soil resistivity. ONTRACK commissioned measurements of soil resistivity within the track corridor and the results were used as a data input. The calculated levels appeared to be, generally, within the limits. Additional measures, in the form of buried earthing conductors and deep mast electrodes, to lower the EPR levels will need to be applied on Onehunga line.

The third, yet to be undertaken simulations, will be to test the system in relation to meeting power quality standards and an assessment of resonance issues normally associated with overhead lines. This work can only be commenced

after the train characteristics become known. However based on previous experience, it can be reasonably expected that power quality issues that will require some form of mitigation are the Voltage imbalance due to single phase loads and high levels of emission of harmonics generated by inverters of the train propulsion system.

Figure 11, Example of Simulator Output, Current Along Line, Siemens 2008

The available technologies, to deal with non-conformances with power quality standards, are expensive and need to be designed to specific situations. The equipment that will be considered, among others, include active filters, Static VAr Compensators and Phase Balancers.

It is also planned that simulations of the system’s performance will need to be repeated if the final timetable, train consists, passenger loading and train characteristics differ significantly from what has been assumed.

4.2 Standards, Codes of Practice and Guidelines

ONTRACK has in place a suite of standards for the 25kV electrified railway on their North Island Main Trunk. The NIMTE line is a single track with several passing loops and is an AT system. Electric locomotives are used to haul freight carriages.

The Auckland electrification required early on, a process of revisiting, updating and development of new standards in line with the latest technology, best practice and experience of similar projects in the world. To enable the electrification works to commence and the system to operate, ONTRACK obtained an exemption from regulation 93 of Electricity Regulations 1997 and Electrical Code of Practice 34:2001 in relation to safety of people and infrastructure. The exemption was given by NZ Ministry of Economic Development Energy Safety. ONTRACK undertook to adopt European standards, the EN suite of documents, related to electrified railways, modified to suit local conditions.

4.3 Feeding configuration



The unavailability of 220kV bulk power supplies in close proximity to the railway network forced ONTRACK to limit the number of substations to 2 being at Penrose and Southdown. These locations are only 2km apart which in turn makes the feeding sections long. To further sectionalise the network several track sectioning cabins are planned. Figure 12 shows the proposed feeding configuration.

Figure 12, Auckland Normal Feeding Configuration

4.4 Challenges

The Auckland electrification, like any railway project, faces challenges that need solutions. This section will discuss a few of those issues.

Successful delivery of the project will depend on proper planning and coordination of other works that are undertaken concurrently to electrification. All works at stations, major structures, track modifications and re-signalling need to be done in close coordination with electrification. The interfaces run deep and wide and include, among many, earthing and bonding, locations of signals in respect to Neutral Sections and overlaps, track centers and turnouts in relation to overhead line tension lengths.

ONTRACK decided to undertake the project in separate phases. The first is the design phase. This will have to be completed before the second phase of construction commences. This strategy provides sufficient flexibility to define the scope of work and determine the technical requirements.

This will work well provided that ONTRACK secures continuity of the services of the designers to assist in resolving unavoidable issues raised at the time of construction. Another challenge associated with this methodology is the accountability of designers and contractors. The solution is a clear and documented scope of work and ownership of the works.

The railway industry is very busy at present. There are a number of electrification projects in Australia alone and the challenge for ONTRACK will be to engage experienced and committed contractors to undertake the works. The risks are the possibility of substandard quality of construction resulting in time over-runs for corrective works. The increased labour cost, high equipment and metal prices may also lead costs to exceed allocated funds.

The railway electrification is also a relatively new concept for local professionals. Architects and structural engineers face a need for in-depth understanding of railway specific requirements. The solution is a timely exchange of information and expertise, workshops and a formal process of interdisciplinary reviews.

Another challenge for ONTRACK is to establish, as early as possible, a team of technical professionals at all levels that will undertake a construction surveillance, gain railway experience, become familiar with the installation and later form a core of the maintenance crew.

The construction will impact on present passenger services as well as on other railway operators sharing the track. An early understanding and agreement relating to duration, number and frequency of necessary track possessions should be sought. ONTRACK will have to arrange for alternative means of transport during the unavailability of present passenger services.

Well before the line is energised, ONTRACK will have to undertake a public campaign of electrification awareness. A comprehensive system of track access permits, procedures for isolations, roles and responsibilities, response to faults and disturbances and general maintenance philosophy will have to be in place and proven working. An example here is the issue of responsibility of maintenance of track bonds. The continuity of track bonds is absolutely essential for the safety of public and railway workers.

Additionally, training of railway workers from other than ONTRACK organisations working on or in the proximity to the electrified network will need to be addressed. This is a long and demanding process requiring the establishment of training centres and the availability of skilled personnel.

There are several stakeholders that are or will be affected by the electrification. These include Telecom NZ, pipelines and overhead lines owners, operators of businesses on leased or adjoining railway land, bridges and structures owned by



local authorities. The solution is early consultations, negotiations and signing agreements with affected parties.

The operations also face an issue of possible excessive wear of contact wire and pantograph carbon strip as well as a momentary loss of contact resulting in current and voltage transients due to low standard of track maintenance. The advised track construction and maintenance tolerances appear to be outside the limits used in modern railways.

Another challenge is the unknown characteristics of future rollingstock. The mechanical and electrical characteristics will impact on the performance of the traction power system if differing significantly from what was assumed for the power study. In addition the required operability of the NIMTE electric locomotives in Auckland causes several restrictions in the design of the overhead wiring system.

The Auckland railway network has a number of level crossings in close proximity of low clearance overbridges. The height of contact line would have to be changed significantly over a short distance. This in turn will adversely impact on the quality of current collection as the pantograph may loose contact at higher speed. Apart from very expensive bridges, height increases or unacceptable closing down level crossings, the

only solution is to reduce line speed. The impact on services will need to be investigated.

5. CONCLUSIONS

The Auckland Electrification project is still a ‘work in progress’. It presents various challenges some of which are typical to similar projects of that nature, others which are unique and specific to the location. The main issue appears to be a lack of suitably located 220kV bulk power supplies that have forced certain level of compromise in an arrangement of feeding configuration. The positive outcome is the possibility of adopting a simple rail return system instead of the originally anticipated Auto-transformer system. The simple system can be installed at a significantly lower cost and will also eliminate a need for aerial to cable auxiliary feeder circuit transitions at several locations of low clearances. The contract procurement strategy by separating the design and construction activities, provided that the roles and responsibilities are understood and processes closely followed, should benefit the project.

6. ACKNOWLEDGEMENTS

The author would like to thank Messrs John Skilton and Allan Neilson of ONTRACK for their comments offered during the preparation of this paper.

1verygood7c2 paper 3 - proposed electric traction for auckland 29 october

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