[All] City of Ottawa - Power Collection and Distribution Systems

[Robert Milligan]

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(TMP) Projects > Light Rail Transit (LRT) Technology Forum > Read all  
about it—LRT technology education begins here > Power Collection and  
Distribution Systems
Read all about it—LRT technology education begins here
Executive Summary
Glossary of terms and abbreviations
Automation versus driver-operated vehicles
Climate Considerations
Low-Floor and High-Floor Vehicle Characteristics and System Implications
Single Versus Multiple Vehicle-type Fleet
Power Collection and Distribution Systems
Regulatory Framework
Degree of Corridor Segregation
Signalling Systems

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Power Collection and Distribution Systems
Introduction
Overview of the power system
Power Distribution Technologies
Dual power systems
System Implications
Applicability to Ottawa
Conclusions and Recommendations
Introduction
Electrically-powered railways provide an excellent way to move large  
volumes of passengers. These systems have been in use for more than a  
century and provide for clean and efficient operations. They allow for  
the power to be supplied by any number of sources and represent an  
important way of future-proofing the system, regardless of energy costs.
An electrical power system emits no pollution where the power is used,  
although some miniscule amounts of ozone will be emitted at the power  
contact points during arcing and sparking; over the last 120 years  
there is no evidence of these amounts being injurious to human health.  
As electricity is centrally produced at power stations that operate at  
or near peak efficiency, the total pollution created is also greatly  
reduced in comparison with other propulsion methods.
The use of electric power in a tunnel environment is relatively safe  
as passengers are not exposed to the noxious fumes generated by  
vehicles powered by internal combustion engines.
Key Issues
Key issues in the selection of an appropriate power supply technology  
include:
Should the design of the power system be concerned only with efficiency?
Climate issues with respect to the reliable operation of electric  
power transmission in Ottawa’s winter months
The potential for a mix of technologies to be deployed
Aesthetic concerns with respect to look of the runningways,  
particularly in sections of the rapid transit network that could pass  
through sensitive areas such as the Greenbelt or the Western Parkway  
corridor.
Overview of the power system
With any electrically powered railway, there are three fundamental  
components which dominate the system.
Power supply: Including the power grid to bring power to the  
transformer stations that convert it from the high voltage  
distributions system a voltage that can easily be transferred to the  
trains.
Power transfer: The means of transferring and distributing energy from  
the transformer station to the vehicle.
Prime mover: A motor or similar device which will allow the  
distributed electrical energy to be converted into a motive power and  
therefore movement.
Power is supplied to the system by Hydro Ottawa at a high voltage,  
likely from the distribution lines that supply power to the city. This  
power is transmitted from generating stations over long distances  
using alternating current. The power is received by the system at  
Power Supply Units (PSU) or Traction Power Substations located along  
the line, which are strategically placed to provide the right amount  
of power at strategic points.
Once the power is received and transformed, it has to be transferred  
to the trains. This transmission can be done as either AC or DC. For  
long distances AC power is commonly used as the high voltages allow  
alternating current for lower or direct current, providing power to  
trains with minimal losses. Rapid transit systems tend to operate on  
DC, which operates at a lower voltage but higher currents and requires  
that power substations be spaced more closely. The lower voltage of a  
DC system also simplify some maintenance and operations and eliminate  
the need for power transformers on all trains operating on an AC system.
In addition to the type of current system used, the method to connect  
to the trains also needs to be considered. Third rail and overhead  
catenary systems are the two primary methods used. The position of the  
third rail down close to track level can make maintenance easier, but  
requires complete segregation of the right-of-way to reduce risk of  
electrocution. Overhead systems require poles and catenary wires to  
support the contact wire that provides the power to the train.
Two new systems are in the development or early deployment stage.  
These do not require either an overhead wire or a constantly powered  
third rail, but rely on either a power rail between the two running  
rails that is live only when the train is sitting over top of it, or a  
contactless system that induces power to the train. Both of these  
systems rely on on-board power storage to augment the system.
Figure 1 shows the power distribution system. High voltage power is  
supplied by the local utility to the Power Supply Unit (PSU) or  
Traction Power Substation where it is rectified and connected to the  
Overhead Catenary System (OCS). The OCS could equally be a third rail  
or ground contact rail, but the concept remains the same. The power is  
then passed through a collector at the top of the pantograph and is  
passed to the propulsion motor (or prime mover). After passing through  
the propulsion motors, the return current is passed back into the  
running rails where it connects back to the PSU.
Figure 1 - Overview of power distribution

AC and DC powered systems
AC systems are predominantly chosen for rail networks which have long  
distances to travel and require fewer power supplies. There are some  
systems in Canada which operate from 25kVAC including the Deux  
Montagnes Line in Montréal. This commuter rail line was originally  
powered by 3kVDC but was converted when it was reactivated in the  
1980’s.
Despite the appealing reduction in electrical infrastructure costs and  
lower power losses, the 25KVAC system requires the vehicle to carry  
its own power transformers on-board which leads to a large increase in  
vehicle weight and a loss of vehicle space. The higher voltage system  
also carries a higher risk of safety for passengers and operating  
personnel. Higher voltages also produce stronger localised  
electromagnetic fields which can cause EMC problems with adjacent  
equipment, and without adequate screening can also increase risk of  
biological exposure both inside and outside the vehicle.
A DC system operates in much the same way as 25kVAC, but requires that  
the AC supply be converted, or rectified, to provide a DC source for  
the trains. The majority of electrically-powered railways in the  
United States and Canada operate at either 600 or 750VDC, with only  
two (which are largely metro/commuter rail lines) operating from  
1500VDC. In fact it should be noted that the original Ottawa North  
South Line was designed to be fitted with a 1500VDC system.
The DC system requires local Traction Power Substations to be  
regularly spaced at approximately 1.5km intervals at the trackside  
should one substation fail. These allow some redundancy of operation.  
The net benefit is that the power transformer equipment is not carried  
on-board the vehicle, leading to a lower vehicle weight and gains in  
interior space.
There are some important distinctions in vehicle types which are  
related to the size and amount of power equipment stored on-board the  
vehicle. LRV’s associated with LRT tend to have power equipment stored  
locally and in some cases in the roof space to maintain a low floor  
and maximise interior space. Metro and EMU vehicles have equipment  
which is of a larger size and weight and is proportional to the  
vehicle size, speeds and weight increase. Also Metro and EMU vehicles  
tend to have higher floors and so the associated power equipment has a  
greater ability to be located underneath. The EMU vehicle, to gain  
even more space, tends to be coupled in multiple units, which allows  
the sharing and distribution of equipment underneath two vehicle  
bodies which means that they cannot easily be separated; this  
technique is also common across all vehicle types, but the EMU design  
and size allows more flexibility.
Power Distribution Technologies
Due to their lower voltages, DC systems have a number of different  
available methods of power transfer, including:
Third rail
Overhead catenary
In-ground power rail
Inductive power transfer
AC systems however are generally limited to either an overhead  
catenary system or inductive power transfer.
Third rail
Third rail is used predominantly in areas of narrow rights of way or  
in tunnels where the objective is to reduce the width of the running  
route or the overall diameter of the tunnel bore. Its compact  
configuration can allow for substantial tunnel savings over that of a  
tunnel diameter that supports an overhead system. The cost of  
installation and maintenance is also low, as the system is all ground  
level based and easily accessible.
A number of third rail systems use the running rails as a negative  
return although one of the biggest users of third rail (London  
Underground in the UK) use a separate return conductor which is  
actually a fourth rail and removes the need for using the running  
rails as a return path for the current. Vancouver’s SkyTrain also uses  
a third and fourth rail for power distribution and return.
The close proximity to ground makes the electrified third rail system  
a significant operational hazard. Work safety conditions can easily be  
compromised in wet and slippery environments. Passenger access needs  
to be more carefully controlled to prevent accidents.
Its close proximity to ground level means that the electrical  
insulators supporting the third rail suffer from brake dust  
contamination and insulation cracking which lead to stray currents.  
They are also prone to ice and snow shorting the electrical system to  
earth. Newspaper and other litter at track level can also get caught  
in the paddles used to pick up the power causing small fires.
The third rail system requires segregation from the public as access  
to the rail is relatively easy. In station areas the third rail is  
moved to the other side of the platform to minimise the possibility of  
electrocution. Third rail systems are generally fitted with high floor  
vehicles to decrease the likelihood of passengers being in the track  
area.
Third rail is a proven and mature technology and there is a degree of  
competition in the manufacturing of components, but aspects of safety  
mean that the system is no longer in favour and is now becoming quite  
specialised.
Overhead Catenary Systems
Overhead systems are the most common form of power distribution to LRT  
vehicles throughout the USA and Canada. Most of the existing LRT  
systems are 650-750VDC overhead catenary with a small number of metros  
operating at 1500VDC.
The advantage of overhead systems are that they don’t require a high  
degree of segregation from the public, but will require additional  
safety precautions, permit procedures and revisions for ‘working at  
height rules’ in any publically accessible areas.
Some careful planning of the pole positions in visual alignment to  
trees or the growing of vines and creepers on catenary infrastructure  
will help to soften the visual impact of the overhead system and gain  
wider public acceptance.
The overhead system carries electrical current to the vehicle via a  
suspended wire called the catenary (slotted cable) along the track  
layout. The catenary wire is suspended on a messenger wire between  
poles that are typically spaced every 50 metres.
The overhead system will require sizing for temperature extremes to  
prevent sag in the summer and ice build-up in the winter, to achieve  
this, and maintain constant tension in the catenary wire, a system  
with counterweights is integrated into the support poles.
Two wire catenary systems exist where an additional catenary wire acts  
as the current return. These are predominantly found in systems where  
the electrical current cannot be passed into the rail for reasons of  
isolation or risk of stray current. The two wire system and its  
additional wire necessitates the use of two collectors or two trolley  
poles which are at risk of icing and poor contact. In addition the  
negative and positive of the supply are in close proximity and require  
careful isolation to prevent short circuits across the traction power  
supply system
The minimum size of catenary wire is related to mechanical strength  
and is related to line speed of the LRV, the overall resistance of the  
wire and the current required for the vehicle. Thicker wire reduces  
volt drop and power loss at the increased expense and visual intrusion  
of the wire. It is not common to operate a system with different wire  
sizes, for reasons of electrical safety.
To reduce wire size, there are three options for the designer:
Reducing the spacing of the traction power substations, with the  
result of having more substations.
Increasing the working voltage.
Provide on board power storage.
Techniques of overhead system design and installation can be married  
with modern mechanical support structures to improve the look and  
aesthetics of the system.
Like third rail, overhead systems require similar maintenance and  
safety techniques and there is a good technical understanding  
worldwide. The result of overhead systems being widely accepted is  
that there are a number of competitive manufacturers to choose from.
A major disadvantage in Ottawa is that poles, messenger wires and  
catenary wire can be loaded by frequent ice build-up and the  
supporting structures will need to be able to compensate for the  
additional weight during the winter season.
In-Ground Power rail (APS- Innorail)
Currently the only In-Ground Power Rail system or APS (Alimentation  
Par Sol) system is Alstom’s Innorail, which is a relatively new  
concept which removes the controversial overhead wires and poles, and  
places the catenary underneath the vehicle as a contact strip. In  
reality this is similar to the third rail principle, except the  
contact strips are only energised directly underneath the vehicle to  
ensure maximum safety of pedestrians. As a safety precaution, once the  
vehicle passes over the contact strip the device is grounded to remove  
any residual current.
Figure 2 - Alstom In-ground power rail

The system is in operation in a few European cities, which have a much  
milder climate, and therefore does not represent conditions that would  
be expected in Ottawa. When located on a paved roadway, the contact  
strip is exposed slightly above the tie or paved surface and a  
consequence is that the contact strip may suffer from ice and salt  
build-up across the conductors that may result from freezing rain and  
poor drainage, in a typical Ottawa winter.
As part of this project, Alstom were asked how this could be mitigated  
and they responded that some form of ice scraper could be fitted at  
the front of the train to clear this away, the area around the contact  
strip would have to be designed with good drainage and the contact  
strip could be electrically heated to keep the strip clear. All of  
these options will add to the cost and complexity of the system.
As with third rail, Innorail provides a major advantage in the tunnel  
area as the bore size can now be reduced to its minimal size.  
Furthermore the Innorail system is now a maturing technology which  
also supports mixed operation with catenary and provides the best  
aspects of both systems. As Innorail can be used in the tunnel areas  
it is not exposed to the harsh Ottawa climate and the only areas where  
it would pose some risk to system operation are the exposed visually  
sensitive areas.
An obvious major disadvantage is that there is only one manufacturer  
that has successfully implemented this system. Reports of its  
maintenance difficulties have been keenly discussed but are related to  
the initial Bordeaux system which was the pilot project. As the system  
is predominantly buried below ground it has had an early history of  
unreliability which has been masked by the ability of the vehicles to  
also run on batteries through the unpowered sections. The mitigation  
against powered sections remaining live will require further safety  
analysis.
The system requires many smaller, in-ground power control segments  
that may reduce the overall system reliability and availability;  
however in balance this method may be safer than the permanently live  
third rail system.
As the system is relatively new the ability to recruit experienced  
personnel will be severely limited and as such additional training  
will be required to service and maintain the components.
One important aspect of APS is that the weight of the vehicle  
increases by approximately 1000kg, leading to increased running costs  
and power consumption, but more importantly the ability to regenerate  
energy into the power distribution system is no longer possible.  
Therefore the vehicle either has to store the energy locally or  
dissipate this into a brake resistor (see the regeneration discussion  
below), which must also be carried in the vehicle.
The complexity of APS will also require additional design effort in  
track layout, drainage and ice and snow clearance.
The ability of APS to operate in combination with a 1500VDC system has  
also been assessed and there may be complex issues to resolve with  
compatibility.
Of more of a mechanical nature, gradient changes also have to be  
managed to ensure the contacts remain electrically connected to the  
contact strip as the train moves up and down hills.
Inductive Power Transfer IPT (Primove)
There are currently two manufacturers of similar Inductive power  
transfer systems; Wampfler AG and Bombardier.
The Wamplfer AG system is the more mature and has two formats:
In track loop (shown below).
Local inductive coils to assist with charging on board storage devices  
at strategic points on the network.
As the name implies, IPT utilizes the inductive coupling between two  
electrical circuits, one based at the track level and one located  
underneath the vehicle, to transfer the required electrical energy  
without the need for a direct (conductive) electrical connection as  
required by APS.
The process is not new and can be found in transformers and induction  
motors. The effectiveness and the efficiency of the energy transfer  
depend on the degree of coupling (or the mutual inductance) of the two  
circuits.
The amount of mutual inductance and therefore efficiency is increased  
by reducing the separation between the two circuits. To improve  
inductive coupling further the number of windings on the coils of both  
circuits can be increased however, in the case of a mass transit  
solution, it is typically more cost effective to increase the number  
of windings on the vehicle circuit rather than placing a large number  
of turns in the multi-loop coils in the track bed.
The Wamplfer system has two variants; one has the in-track loop laid  
continuously along the complete alignment, to provide energy  
continuously to the vehicle. This approach needs neither batteries for  
energy storage nor other on-board energy sources, such as a diesel  
engine, although the vehicle can be complemented by these.
The second variant has discrete coils located at various locations  
along the route, to permit rapid charging of on-board energy storage  
devices, typically batteries.
Figure 3 Wampfler -IPT (Continuous Inductive loop)

Figure 3 shows the Wampfler continuous inductive loop system. The  
track supply provides electrical energy to an in-ground loop of  
electrical cable. This loop has track capacitors to tune the loop to  
the track supply frequency, thereby increasing the amount of current  
flow. The high currents create strong magnetic fields and consequently  
transfer more electrical power to the vehicle. The pick-up is  
installed on or underneath the vehicle and arranged to be in close  
proximity to the track, in order to maximize the mutual coupling with  
the magnetic field created by the track loop. A variable frequency  
inverter converts the rectified DC voltage to a variable voltage;  
variable frequency (VVVF) supply in order to control the speed and  
torque of an AC induction motor that propels the vehicle. It should be  
noted that although the example shows an AC induction as the drive  
motor, it is expected that a PWM converter could also be used to drive  
a DC motor.
While there are a number of successful applications of continuous IPT,  
These applications are specialized and have low speed and low power  
requirements. None have the power capacity to provide a typical 600 kW  
required by an electric vehicle. The continuous IPT system has not yet  
been tested with a transit vehicle and, at this time, may not be a  
viable candidate for Ottawa.
Bombardier’s Primove is currently a working prototype system and  
therefore carries some risk in implementation. It is currently only  
fitted to a 1-km test track and has not reached the maturity level  
expected of a modern transit system.
Inductive power transfer systems offer some major advantages over  
electrical contact systems as the device works primarily from  
inductive or magnetic coupling underneath the vehicle.
The Primove system can be seen as a variation of the vehicle carrying  
its power supply transformer as in the case of the 25kVAC system. As  
such there may be a weight penalty associated with the train-based  
equipment and therefore subsequent operating and running costs.  
However the literature available shows a large air gap transformer  
with a small loop acting as a primary winding and the vehicle  
supporting the transformer and secondary inside.
Transformers operating with large air gaps are not uncommon; however  
the design of the transformer is unknown. It is highly likely that the  
primary is fed with an alternating current to maximise coupling  
efficiency and the secondary voltage within the vehicle is then  
converted into DC. It is important to note that both the Wampfler and  
the Bombardier systems also make use of alternative storage  
technologies (ultra-capacitors and batteries as described later). The  
bulk of the energy is derived from the on-board storage units with the  
IPT providing the ‘top-up’ of energy, through the in-ground induction  
loops to keep them electrically charged.
The “in-ground” or buried induction method of power transfer offers a  
high degree of safety as the primary induction loop, is insulated and  
unexposed to the public. It is contact-less, meaning that there is  
little or no maintenance involved, with the added advantage that no  
catenary is required.
The insulation of the system also provides a degree of protection from  
the climatic conditions experienced in Ottawa and therefore it  
promises to offer a higher degree of reliability. However like  
Innorail, the track-based infrastructure to support the primary  
windings and the control of the various electrical sections is likely  
to be costly.
Depending on the frequency of operation the magnetic or inductive  
coupling may also produce some local electromagnetic effects.
There is currently no information on the possibility of regeneration  
of energy and in the absence of any information from Bombardier, it is  
very difficult to speculate if this is actually possible.
Regeneration /Ultra-capacitors, batteries and energy storage
Regeneration
Regeneration or Regenerative braking is a process where the energy  
supplied to the vehicle is reconverted back into electrical energy and  
supplied to other equipment when the brakes are applied. Unlike  
internal combustion engines, this is the major benefit with motors and  
electrical systems as they can minimize waste energy, reduce annual  
power consumption and therefore running costs. In terms of  
sustainability an electrical system that provides for regenerative  
braking is a better solution for overall energy efficiency.
Regenerative braking is the conversion of the train's kinetic energy  
to electrical energy by using the traction motors as a generator. The  
generated electrical energy flows as current back into the supply  
system or into other connected loads. In principle this is easier with  
DC electrification than with AC electric railways, because AC systems  
require the phase and frequency of the generated electricity to be  
matched to that of the overhead line equipment, although AC  
regenerative systems are common.
With a DC system, the vehicle cannot easily return any surplus power  
back to the Hydro Ottawa power grid, however if other vehicles are  
operating on the same track section then the excess power can be  
transferred to another vehicle. If no train is available then a  
braking resistor is used to dissipate the energy as heat.
With AC systems regeneration is more complex but is still possible  
under thyristor control.
As the overhead lines are fed from different phases of the grid and  
the overhead wire is fed in distinct sections this can be difficult to  
accommodate. Along neutral sections a dynamic braking resistor is  
required for when the train is required to slow down. However, the  
power converters of a modern AC train can perform regenerative braking  
reliably. The regenerated AC energy is able to return to the supplying  
grid and be used elsewhere. The regenerated power from an AC system in  
fact is a reverse load on the power distribution system, which results  
in a slight rise in the system voltage. This rise in voltage results  
in an overall reduction in energy supplied by the generating stations  
on the grid network.
Regenerative braking is the most efficient on a busy line. Some  
reports indicate that DC regeneration is more effective when 6-10  
train per hour are expected and will lead to a 12-16% energy saving  
and AC regeneration is effective at 2–10 trains per hour and  
represents a 12% energy saving. As real examples, Lisbon metro  
regenerates 30% of its power and Delhi Metro regenerates 34%. When  
considering that 5-15% of the operating cost of a light rail system is  
attributed to electrical power consumption and that 60-80% is  
attributed to traction power, it is easy to understand the priority in  
reducing overall running cost.
Earlier AC and DC electrical systems used rheostatic brake resistors  
to absorb the regenerated power, however this necessitated loads to be  
switched in or out of circuit depending on system load and so is not a  
favoured approach by today’s standards.
The ability to regenerate power provides major savings for an operator  
over the lifetime of the network and therefore reduces the  
environmental footprint. Moreover there is a reduction in wheel and  
brake pad wear and an improvement of the mechanical braking system,  
which assist in minimizing the overall running cost of the vehicle.
It should be noted that a train doesn’t use electric braking for its  
whole deceleration cycle. Once it gets to a lower speed, electric  
braking (the effect from regeneration) blends into friction braking  
from either pneumatic brakes or electric track brakes. During electric  
braking the train control software can efficiently blend the levels of  
regenerative, rheostatic, friction and pneumatic braking, providing a  
safe, efficient and smooth brake.
Storage of energy
In a traditional electrified rail system, and in the absence of  
another vehicle on the catenary, the regenerating vehicle is forced to  
waste the regenerated energy as heat into a brake resistor, which  
leads to localised temperature rises on the vehicle or dissipation of  
heat while the vehicle is stationary. The waste heat can cause  
uncontrolled temperature increases in or around the vehicle, which in  
turn leads to early component failure. To mitigate this effect the  
vehicle requires additional cooling and power, which leads to  
increased running costs. When a train is stopped at a station area,  
the dissipated heat will also cause a higher ambient temperature rise,  
which necessitates additional air-conditioning for that location,  
which leads to higher running costs.
To even out the power usage the electrical system should offer a means  
of energy storage in the following locations:
At the wayside: By having the energy storage at the wayside in a  
number of strategic locations, the vehicle carries no additional  
weight and the energy storage system can be separately housed and  
temperature controlled. However if the power section fails due to a  
circuit breaker or fault the device will not be available for local  
power storage.
On the vehicle: The train will have additional weight to carry, but  
has a secondary source of power in the event of a section losing  
power. This means that the vehicle can operate (depending on energy  
storage capacity) to the next powered section. Mannheim LRV can  
operate at lower speed of 26km/h for 500m without catenary power and  
more importantly in the case of Ottawa, if the vehicle experiences  
poor contact on the overhead catenary due to ice formation, it will be  
able to maintain speed until electrical contact can be regained. On- 
board storage coupled with the support of in-ground rail or inductive  
power may allow the vehicle to travel through the greenbelt and  
parkway without catenary.
An additional benefit of energy storage is the ability to have more  
flexibility in the placement of traction power substations such that  
the limitations of permissible volt drop associated with catenary line  
length are reduced.
Storage technology
A number of technologies have surfaced to allow the recovery of the  
regenerated energy these broadly fall into three formats:
  	
Rate of charge/
discharge
Life expectancy
Cost/power storage
Power density /weight
Limitations
Competition
Ultra-capacitor
Very short charge time
High
High
6kWh/kg
Cost
Sole sourced
Flywheel storage
Short charge time
Unknown
High
4kWh/?
Safety /
Under development
Fewer manufacturersbut existing proprietary knowledge.
Battery
Long charge time
Limited life
Low
30 – 160Wh/kg
Weight /Maintenance
Many
Potential application of storage technology
  	
OCS free
Peak power smoothing
Frequent service and service stops
Infrequent service and service stops
Ultra-capacitor
Limited OCS free use
Yes
Yes
No
Flywheel storage
Limited OCS free use
Yes
Yes
No
Battery
Yes
Limited use for smoothing
No
Yes
Ultra-capacitor (Maxwell industries)
The Ultra-capacitor or ‘Super-capacitor’ is a newer technology that  
uses the properties of an electric double layer capacitor (two layers  
of carbon either side of a porous dielectric material sandwiched  
between the outer electrodes), which enables very high capacitance but  
at a low operating voltage.
Large numbers of these are arranged in series to provide the correct  
working voltage at the expense of a reduction in series capacitance  
and these series capacitors are then banked to retain the required  
system capacitance. Maxwell industries claim working voltages up to  
1500VDC.
The advantage of the ultra-capacitor is that it has a high charge/ 
discharge rate and can absorb the immediate energy produced by  
regeneration. In effect the ultra-capacitor has battery storage and  
can propel or power the system for short durations. The low ESR  
(Equivalent Series Resistance) means that power loss in the device is  
small and the units can run at typically 95% efficiency.
Figure 4 - Vycon Flywheel cross-section

The Vycon Flywheel shown in Figure 4 is representative of flywheel  
technology. Simply, it is a motor with mass, which is spun using the  
regenerated power from the train. This mass continues to revolve in  
virtual vacuum and magnetic bearing, which removes friction losses and  
allows the unit to spin indefinitely (although there is some gradual  
degradation in speed over time). The unit will produce power when the  
overhead catenary system requires additional capacity such as another  
vehicle entering the powered section.
An important feature of the flywheel is its compactness and the  
ability to locate the unit either within the vehicle or outside near  
the traction power substation. Location of the unit on the vehicle  
will incur some weight penalty and therefore additional operating  
cost. There also may be a risk with having high speed rotating  
machinery in close proximity with passengers and the effects of  
inertial energy on the vehicle may also need consideration.  
Maintenance history of the units is unknown and the vacuum sealing is  
quite specialised, however the core technology of mass and brushless  
motor is mature. There is a small delay in charging the rotational  
mass, therefore there will be some minor power conversion losses.
Battery (Various manufacturers)
Battery storage is a proven and mature technology. It provides a  
relatively good weight to power ratio and low cost. One of its major  
disadvantages is that the battery is affected by temperature, which at  
low temperatures results in loss of capacity, and at high temperatures  
can cause plate buckling which causes short circuits and loss of  
voltage, or in extreme cases can result in electrical fires. A common  
misconception is that the battery can be rapidly charged and  
discharged, however, although the device is resilient to rapid charge  
cycles and deep discharges this can result in some loss of battery  
life expectancy and overall performance. A further disadvantage is  
that most batteries require routine maintenance and inspection and  
also regular charge and discharge cycles to maintain peak performance.
Battery technology is mature and widely understood and the choice of  
competitors ensures that costs are kept to lower values. The more  
lightweight higher capacity battery types are quite specialised and  
fewer manufacturers exist due to patent protection.
Dual power systems
One of the important aspects of an electrically powered vehicle is the  
flexibility in power system design. Most manufacturers will  
accommodate a client’s design requirements and so decisions on the  
technology implemented should always be tempered with a detailed  
analysis of the cost-risk-benefits and the practicalities of  
developing a mixed power system.
A dual power system is generally considered when there are areas of  
city which force a restriction in the use of overhead catenary for  
power transfer for perhaps reasons of clearance, effects of stray  
current or visual sensitivity in the surrounding area.
The adoption of a catenary system with additional attention paid to  
its generic design and pole placement will carry less of a risk in  
comparison with the merging and ongoing development of two separate  
power systems. However the benefits of a dual system should not be  
overlooked and with an ‘all-electric vehicle’ the ability to lower the  
pantograph during operation in the tunnel will realise significant  
cost benefits in tunnel construction due to the potential in bore size  
reduction. In comparison a diesel electric vehicle will allow  
significant reductions in overhead infrastructure and minimise the  
impacts of utility relocation due to possible effects or risks  
associated with stray current.
Dual power systems will broadly take the following formats:
Catenary – Onboard power storage.
Catenary – In –ground power rail (APS including some onboard storage).
Catenary – Induction power Transfer (IPT)
Diesel-Electric
In all four formats there will be a consequential increase in weight  
and running cost and the ability to regenerate into the power system  
may be reduced or lost. Note that third rail is not considered a  
candidate as part of a dual power system as the location of the power  
collection paddles at mid-wheel height poses an electrical hazard if  
another means of powering the train is provided and the subsequent  
electrical isolation/protection fails.
Catenary – Onboard power storage Combination
A dual power system would operate mainly from catenary with the  
vehicle operating from batteries or ultra-capacitors for short  
unpowered sections of up to 500 metres (batteries will allow for  
greater distances than ultra-capacitors). The on-board storage would  
then recharge once the vehicle has reached the catenary section on the  
opposite side. There is a risk of ‘stranding’ of the vehicle and  
consequent disruption to the network if a battery failure or  
electrical storage fails. The vehicle cannot regenerate in the  
unpowered section and so energy will be lost as heat in the brake  
resistor.
Catenary – In ground power rail (Innorail) Combination
This system is a likely candidate as there are a number of Innorail  
systems already operating in dual power mode and therefore it is  
becoming a more mature technology. A risk area will be its use in  
exposed external areas; however a number of suggestions have been made  
to mitigate this and are roughly in line with the methods proposed for  
protecting turnouts and other rail infrastructure. Of particular  
interest must be its inclusion in the tunnel area where the system is  
not excessively exposed to the harsh climate. The use of Innorail will  
allow the train to lower its pantograph before entry into the tunnel  
area and run on Innorail through to the portal exit whereupon the  
pantograph will be raised on the other side.
There are some design challenges to ensure the pantograph is lowered  
and raised before and after the tunnel and that ice and snow build up  
do not affect operation, however these are not insurmountable and have  
effectively been achieved, albeit in different environments.
If a Catenary-In–ground power rail system was enhanced with additional  
power storage most unplanned failure scenarios may be mitigated.
Catenary – IPT Combination
There is little data on the working of the IPT systems, however it is  
not unreasonable to assume that mixed catenary, energy storage and IPT  
is possible as with Innorail. However it would be expected that  
regeneration would be less efficient over the inductive loop and more  
complex within the vehicle. The smaller coil based loops would not  
permit efficient regeneration.
Diesel-electric
A number of European cities use a propulsion method which allows the  
vehicle to be powered by a mix of electrical overhead catenary in  
densely populated areas, and run on the power generated by a diesel  
combustion engine outside of cities. For Ottawa, one important aspect  
of this technology is that the Diesel- Electric vehicle can run on  
diesel power out of the tunnel and once in confined areas can switch  
to electric power; where the risk of exhaust pollution is considered  
too great.
Most of the major vehicle manufacturers offer a diesel-electric dual  
mode vehicle:
Alstom’s - Regio Citadis.
Bombardier’s -Flexity, Talent.
Siemens - Combino.
Ansaldo-Breda – (dual power buses but no information on LRV’s,  
although reports indicate that they exist)
The dual mode vehicle has a number of advantages:
The implementation of overhead catenary can be implemented in stages  
over longer periods, therefore lowering capital costs.
The need for relocation of utilities in the non-electrified areas is  
minimised as there is only need for utility relocation for reasons of  
access rather than stray current protection, therefore cost and  
impacts to highways are minimised.
Similar to BRT, the right-of-way can be established early on and at  
comparable costs, which then permits easier migration to electric LRT  
once ridership is established.
It is a flexible technology. In certain vehicles, engine can be  
removed as retrofit and vehicle returned to electric only operation.
The vehicle can be refurbished at a mid-stage lifecycle and converted  
to all-electric LRT.
In the event of a power failure the vehicles can operate and provide a  
reduced service.
Its perceived disadvantages are:
Depending on vehicle type, the turning radius can be limited by the  
Cardan shaft connection from the diesel engine to the truck.
The vehicle has to carry the additional weight of the diesel engine  
and its fuel.
Low floor vehicles limit the ability of mounting the engine underneath  
the vehicle. Engines can protrude into passenger area and reduce space  
or require to be fitted to the roof space.
Diesel, although requiring high temperature or pressure to ignite, is  
nevertheless a flammable fuel.
Noxious fumes and particulates produced by the exhaust of a diesel  
engine increase the risk of Eczema and Asthmatic conditions for  
passengers.
Additional weight requires increased power needs within the electrical  
powered sections.
If poorly controlled, the noise of the diesel engine can be fatiguing  
on passengers.
Diesel engines require more regular maintenance than a pure electrical  
system.
The system requires strategic filling stations for fuel.
Operational costs are related to fluctuating oil prices.
Examples of Diesel -electric vehicles
Two dual mode low floor vehicles manufactured by Stadler are used on  
the ‘River line’ New Jersey and by Capital Metropolitan Transportation  
Authority (Capital Metro) in Austin Texas. These are effectively  
vehicles fitted with diesel generators that provide power for the  
electric traction motors with no pantograph, although reports state  
that the vehicle is available in mixed diesel engine /overhead pickup  
configuration.
One of the major benefits of the diesel generator /electric drive from  
Stadler is that the vehicle has a better turning radius than that of  
the shaft driven vehicles.
Of significant importance are the dual mode vehicles used in Europe in  
the cities of Kassel and Nordhausen.

Figure 5 – Gelenktriebwagen used in New Jersey and Austin (picture of  
Swiss overhead catenary vehicle)
Kassel (Regionalbahn) Tram trains
Kassel has a large LRT network of 122km with a mix of vehicles. To  
reduce electrification costs Kassel operates dual mode Alstom Regio  
Citadis vehicles that are fitted with roof mounted diesel generators.  
The use of roof mounted diesel generators ensures that the city  
maintains the use of a low floor vehicle for improved accessibility.  
However, these vehicles have a reduced standing capacity due to the on- 
board storage of the fuel.

Figure 6 - Kassel Tram
NordhausenTram trains
The Nordhausen vehicle is based on the Siemens (formerly Duewag)  
Combino Duo. This is a 750VDC electric vehicle with 180kw Diesel  
engine generator. Of particular note is Nordhausen’s population size  
and density: 44,742 people and 421 people /km2 respectively.

Figure 7 - Nordhausen Tram-Train
The use of the Combino Duo minimizes the cost of electrification of  
the entire city and therefore reduces the total cost of installation  
and infrastructure in the city centre.
The picture below shows a typical loss of standing space attributed to  
the extra equipment required for diesel-electric power.

Figure 8 - Inside of the Combino Duo
System Implications
Safety
Safety is paramount in any public transit system as this increases  
passenger confidence and therefore builds ridership.
Any exposed power system has significant risk associated with it and  
behaviour and work patterns around the system must be modified and  
controlled to maximise public safety and the safety of the operating  
personnel.
The primary mitigation for an abnormal electrical system failure will  
be either;
Emergency electrical isolation of the supply, or
Localised ‘Intertripping’ between substations.
This is to prevent:
The immediate risk and danger of equipment malfunctioning and/or  
electrocuting /injuring passengers and personnel, and
The danger of fire spreading in the Tunnel and Depot.
Isolation also prevents:
The danger of a train being powered while being serviced/ repaired
To maximize safety and assist in the detection, communication and  
management of such events the electrical power system should be  
complemented with the following:
Installation of system wide and local emergency stop push-button, CCTV  
and panic alarm system.
Installation of early warning fire detection/alarm systems.
Adequate training of staff and liaison with fire and emergency  
services regarding electrical fires and tunnel evacuation techniques.
Installation of interface systems that will disable the CRV supply  
whilst the LRV is under maintenance or repair on the track.
Stray current
Stray current is the effect of current passing from a DC source to  
earth via a buried conducting surface and is caused by:
Metal objects coming into contact with ballast and rail, or
Failure or breakdown of insulation.
It should be noted that AC systems do not suffer the noticeable  
effects of stray current associated with DC systems.
The separation of the DC power system from the electrical ground is  
very important, as a failure to insulate causes the stray current to  
damage or weaken buried metallic objects (both old and new) and the  
facilities owned by the transit operator or others in the locality. In  
turn this leads to excessive maintenance and repair.
Typical examples of metallic objects found in an urban rail system are:
Rebar in the supporting walls, platforms and tunnels
Bridge decks
Support Piers
Bolts and fixings
The degree of insulation between the power system and electrical earth  
is a compromise between the need to control any accessible metallic  
objects that have a touch voltage, and the need to limit any stray  
current leakage.
As previously described, the system will be operating a negative- 
return traction power system; where the running rails will form the  
return conductor path, and unlike domestic supplies, these are  
deliberately not connected to ground (the exception is the Maintenance  
and Storage Facility, which under normal conditions is grounded  
separately).
In the absence of stray current control the return current follows the  
least resistance path to earth and in the case of soil and ferrous  
objects causes an electrolytic (Anodic) effect which can rapidly  
corrode any electrically conducting objects and in severe cases can  
lead to structural failure.
Effects of stray current
Causes problems for utilities due to current flow on utility pipes and  
cable sheaths and causes electrolytic corrosion
Reduces power efficiency of the DC system
Causes corrosion to adjacent ferrous or conductive objects
Damages bridge bearings, structures and pipes
Can cause leakage of liquids
Damages domestic power and telecommunication services
Can cause explosion in pipes.
Stray current mitigation measures
Many modern transit systems have a number of corrosion mitigations and  
procedures to eliminate stray current and its corrosive effects:
Provide secondary measures of stray current collection using collector  
mat underneath the rails. This also has the benefit of allowing the  
regular measurement of current but also allows remote monitoring and  
sectional isolation to determine leakage paths.
Monitor stray current at appropriate collector mat zones or ground  
electrodes.
Measure the system voltage at each collector mat (Rail to Ground tests).
Regularly measure track to earth resistance.
Ensure that there is a high resistance path for any leakage between  
rail and earth.
Provide isolation of rail and tie or alternatively provide isolation  
mat underneath track bed.
Ensure design does not inadvertently provide path to ground through  
items that are connected to track .i.e. from rail heaters or switch  
machines.
Provide cathodic protection to control corrosion on unprotected buried  
structures (Pipelines carrying flammable materials).
Keep track clear of debris and dirt through regular maintenance,  
particularly at crossings or paved areas.
Provide monitoring points at substations to measure stray current.
Electromagnetic Interference and Electromagnetic Compatibility
The choice of power system must consider the effects of EMI on  
surrounding areas and the electromagnetic compatibility of equipment.
One of the disadvantages of a higher voltage AC system is that the  
conversion equipment produces considerable electrical noise and  
electromagnetic radiation which requires careful analysis and  
filtering. These effects can interfere with local radio reception,  
contaminate domestic supplies and cause intermittent problems with  
electrical equipment. In the instance of AC systems in remote  
locations this is not necessarily a problem, however the high voltage  
catenary and proximity to residential areas in city environments may  
be challenging in preventing the catenary from radiating or coupling  
with adjacent electrical apparatus and will therefore necessitate  
larger electrical clearances.
It should be noted that the DC systems also suffer from similar  
effects but as this is at a lower voltage, some effects are less  
pronounced and controllable with appropriate filtering.
Operation in extremes of temperature
The climatic conditions of Ottawa pose some significant challenges to  
the system designer. There are few examples that emulate the same  
climate, with the exception of Calgary and Edmonton; both of which are  
DC catenary based systems.
The annual mean temperature range can vary between -15 degrees Celsius  
in winter to +26.5 degrees Celsius in summer. Wind-chill factors in  
winter and humidity in summer also bring about higher extremes.
Three notable weather aspects that will present design challenges are:
Freezing rain, which can cause additional loads on catenary or coat  
contact surfaces so that electrical contact cannot be made and prevent  
adequate drainage.
Thermal swings – rapid temperature fluctuation which can cause thermal  
shock on external components or rapid condensation.
High humidity. – Causing poor cooling or heat dissipation leading to  
equipment infant mortality or premature in-service failures.
Comparable weather systems
St Petersburg (Russian Federation) – Using PTMZ and Siemens vehicles
Month
Temperature
Relative humidity
Average Precipitation (mm)
Wet Days (+0.25 mm)
Average
Record
Min.
Max.
Min.
Max.
a.m.
p.m.
Jan
-13
-7
-32
3
86
84
35
21
Feb
-12
-5
-33
3
81
73
30
17
March
-8
0
-26
12
85
70
31
14
April
0
8
-13
20
79
65
36
12
May
6
15
-4
27
69
57
45
13
June
11
20
2
29
68
53
50
12
July
13
21
5
33
75
61
72
13
Aug
13
20
1
31
79
61
78
14
Sept
9
15
-2
29
86
68
64
17
Oct
4
9
-8
18
88
78
76
18
Nov
-2
2
-18
12
89
85
46
18
Dec
-8
-3
-23
5
88
86
40
22
Ottawa
Month
Temperature
Relative humidity
Average Precipitation (mm)
Wet Days (+0.25 mm)
Average
Record
Min
Max
Min
Max
am
pm
Jan
-16
-6
-36
12
83
76
74
13
Feb
-16
-6
-37
12
88
73
56
12
March
-9
1
-37
26
84
66
71
12
April
-1
11
-19
30
76
58
69
11
May
7
19
-6
34
77
55
64
11
June
12
24
1
36
80
56
89
10
July
14
27
3
38
80
53
86
11
Aug
13
25
2
38
84
54
66
10
Sept
9
20
-4
39
90
59
81
11
Oct
3
12
-10
31
86
63
74
12
Nov
-3
4
-23
22
84
68
76
12
Dec
-13
-4
-37
13
83
75
66
14
Helsinki Finland – Using Adtranz (Bombardier) vehicles
Month
Temperature
Relative humidity
Average Precipitation (mm)
Wet Days (+0.25 mm)
Average
Record
Min
Max
Min
Max
am
pm
Jan
-9
-3
-33
7
89
87
56
20
Feb
-10
-4
-30
12
89
82
42
18
March
-7
0
-26
15
86
70
36
14
April
-1
6
-14
21
81
66
44
13
May
4
14
-6
26
70
58
41
12
June
9
19
0
31
72
59
51
13
July
13
22
5
33
76
63
68
14
Aug
12
20
4
30
83
67
72
15
Sept
8
15
-4
24
89
72
71
15
Oct
3
8
-10
18
91
79
73
18
Nov
-1
3
-16
11
90
86
68
19
Dec
-5
-1
-28
9
90
89
66
20
Power requirements
System power requirements are difficult to determine without knowledge  
of the number and type of vehicles used, operating patterns and  
applied technology.
As a guide, traction power substations are typically rated at 1 – 2MW  
(MW or MVA). The number of traction power supplies is related to  
overall track length and are spaced at approximately 1.5 to 1.75 km’s  
depending on working voltage and electrical system design. The  
approximate power consumption of the system will be in the region of  
5kWh/km to 10kWh/km travelled.
Operating Characteristics
The operation of the power distribution is paramount for safe working  
and operational reliability. Energy storage systems on-board the train  
will have local control systems to maintain power and will result in  
additional weight and loss of space. Catenary, third rail and in- 
ground systems will require a control system that will be housed at  
the maintenance and storage facility. The line will be broken into  
electrical sections and at local traction power supply substations  
information regarding the performance of the electrical system will be  
conveyed back to that operations and control centre within the  
maintenance and storage facility. The system will either be  
automatically monitored predefined limits and/or manually controlled  
by operations room personnel.
Continuous monitoring of the system is required to maximise passenger  
safety and to safeguard against ongoing electrical system failures,  
failures which can be produced through natural component performance  
degradation or though unplanned events such as fallen trees across the  
live electrical system.
In the event of a fault condition the operator will isolate a section  
for maintenance or will prevent passage by removing power from the  
power distribution system.
Maintenance
Maintenance is a key aspect of the system as this maintains  
operational performance and safety. Routine inspections on equipment  
(mainly during the night) will be required to meet suppliers’ warranty  
but to also identify weaknesses in the system due to natural wear and  
tear from the vehicles. The simpler and fewer components a system has,  
the more reliable it will be and the less spares are required to  
maintain operations, resulting in minimisation of operating and  
capital costs.
Third rail systems represent the lowest spares need but require some  
regular maintenance and visual inspection due to their ground level  
implementation. However replacement and renewal is very straight  
forward and takes very little time. Wear of contact components is  
compensated by spring loaded shoes on the vehicle which engage with  
conductor rail.
Overhead catenary requires additional spares as the mechanical  
components are smaller and wear accordingly. The current collector at  
the top of the pantograph is spring loaded and compensates more for  
terrain than wear. Contact wires are staggered to ensure wear is even  
across the current collector of the vehicle.
Ice build-up and broken branches can affect a catenary or even cause  
it to fail. As such rewiring equipment and cherry-pickers are required  
to allow maintainers to inspect and re-instate the equipment.
As Innorail and Primove are relatively new systems there is little  
information on maintenance aspects and some of the earlier knowledge  
of the implementation of Innorail in Bordeaux should be cautioned as  
this represented some early development.
However despite the attractiveness of the removal of traditional  
catenary systems, any in-ground system will have a subsequent increase  
in installation and maintenance costs of the equipment. Also, as the  
equipment is ground–based, it is exposed to a very harsh environment  
from the Ottawa weather and potentially exposed to contamination from  
salt and can be considered a less than ideal location. Maintenance of  
buried contact rail and electrical equipment may be difficult and  
result in additional maintenance expense over the life of the system.
Costs
Throughout this paper there has been discussion of relative costs and  
any cost of a system must be broken down into:
Initial capital costs. The adoption of new technologies not only  
incurs some cost but also risk in implementation.
Spares. The number of extra parts required to be held to ensure  
availability of the system and quick replacement of failed components.
Ongoing maintenance costs. Newer technologies have not yet exhibited  
failure modes and so costs are difficult to predict long term.
In addition the choice of system must also take into account the risk  
that certain technologies tie an operator into a potential sole source  
and will run the risk of:
Future obsolescence or cessation of technology and the consequential  
potential one-time buys.
Losing the Manufacturer due to merger or competition.
Escalating cost imposed by the manufacturer.
Poor adoption of technology by other customers.
The figures below are derived from a technology comparison report and  
an interesting comparison can be seen that despite the general  
acceptance of OCS in the USA and Canada, IPT with additional storage  
can provide additional budgetary savings and reduce infrastructure  
costs.
CAD (Million)
Infrastructure
Vehicle
Maintenance
Energy
Total
%
Million/per km
Single LRV +pantograph and OCS
20.8
88
163.2
110.88
383
100%
38
LRV without OCS and with IPT charging stations + battery
2.4
91.2
159.68
77.6
331
86%
33
LRV without OCS and with IPT charging stations + Supercapacitor
2.4
94.4
158.08
77.6
332
87%
33
In ground (APS)
?
?
?
?
1149
347%
115
Applicability to Ottawa
Aesthetic Concerns
Overhead Catenary Systems
Aesthetics of the power system are mainly based on the visibility of  
the messenger wire and catenary wire, along with the poles and related  
electrical equipment. Traction power supplies and ancillary equipment,  
although large can be placed in rooms and buildings and out of the  
view of the public. Public sensitivity is generally heightened when  
the system travels through inhabited areas or attractive natural  
surroundings.
The use of In-Ground, Inductive Power, or Third Rail systems is  
attractive, as they present no visual clutter to the casual bystander  
or resident. However their potential for unreliability in the Ottawa  
climate must not be forgotten. It should be noted that the initial  
fitment of Overhead Catenary does not prevent the future migration to  
APS or IPT after the system has been built.
Grass track
The use of grass track encourages biodiversity, softens the impact of  
the infrastructure and minimises the visual impact of the track.  
However grass can encourage improper drainage and can lead to ice  
build-up and increases in stray current when not maintained. The use  
of grass in the Ottawa climate should therefore be explored in advance  
or as part of a future study after implementation.
Conclusions and Recommendations
Assess the use of a mixed system using Overhead Catenary and an In- 
Ground (Innorail) or Inductive Power System in the tunnel area to  
reduce bore size, however the development of this and the long term  
benefits in terms of sole source suppliers should be questioned.
High voltage AC catenary power systems should not be considered for  
reasons of increased weight of the vehicle and public and operating  
personnel safety.
650-750VDC is the North American standard for overhead catenary. A  
move to 1500VDC would necessitate greater electrical clearances and  
more highly rated components.
The benefits of operating 1500VDC must be weighed against operating  
650-750VDC with additional storage capacity.
The overall benefit of 1500VDC will be in the cost, flexibility and  
quantity of the Traction Power Substation locations and this cannot be  
resolved without further analysis of the electrical system.
To reduce risk, the City of Ottawa could build a pilot track for test  
runs in winter to explore the feasibility of vehicle performance and  
also to train maintainers/installers early in the process.
Appendix A: Power systems in North America
System
Passenger Stations & Car Stops
Double track length (km)
Power supply voltage (DC)
No of substations
Substation Rating
(MW)
Power transfer
Calgary-Train
31
29.3
600
17
2
Catenary and Trolley
Charlotte (Lynx light rail)
15
15.45
750
?
?
Catenary
Chicago Metra Electric(Metro)
49
  	
1500
?
?
Catenary
Baltimore, Central Corridor
28
28.6
750
14
1
Catenary
Boston, Green Line & Mattapan
83
44.4
600
12
3-6
Trolley
Buffalo, MetroRail
14
10.3
650
5
2
Catenary
Cleveland, Blue/Green
33
21.1
600
6+
?
Catenary
Dallas, DART LRT
34
32.2
750
?
?
Catenary
Denver, RTD LRT
17
22
750
?
1
Catenary and Trolley
Edmonton, LRT
10
12.3
600
8
2
Catenary
Houston Metro Rail
16
12.1
?
?
?
Catenary
Jersey City & Newark, NJ Transit
29
23.8
750
4+
?
Catenary and Trolley
Los Angeles, Blue/Green/Gold
36
66.3
750
21
1.5-3.0
Catenary and Trolley
Minneapolis
17
19.3
750
?
?
Catenary
New Orleans, Streetcars
55
14
600
?
?
Trolley
NICTD South Shore line (Commuter rail)
22
75
1500
10
?
Catenary
Philadelphia, City & Suburban
217
49.6
600/635
4+
?
Trolley
Pittsburgh, South Hills
59
27.4
640
6
6
Catenary and Trolley
Portland, MAX
46
52.5
750
34
0.75
Catenary and Trolley
Portland, Streetcar
24
8.1
750
5
0.3
Trolley
Sacramento, RT LRT
30
25.4
750
15
1
Catenary and Trolley
St. Louis, Metrolink
18
26.5
750
12
1.5
Catenary
Salt Lake City, UTA LRT
16
24.4
750
?
?
Catenary and Trolley
San Diego Trolley
48
72
600
33
1
Catenary and Trolley
San Francisco, Muni
215
35.6
600
12
2-8
Trolley
San Jose, VTA LRT
41
43.1
750
15+
1.5
Catenary and Trolley
Seattle/Tacoma
5
0.8
750
2
?
Catenary
Toronto, Streetcars
625
75.5
600
?
?
Trolley
Vancouver, Canada Line ( metro)
  	 	 	
?
?
Third rail
Note the trolley system is essentially the same as the DC OCS however  
the trolley pole replaces the pantograph system allowing a simpler  
overhead and construction.
CON044279
©2001-2009 City of Ottawa 		
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