electrification focus
occupation limitations on the use of the their travel time by over a minute over a tested. The 2010 timetable with a new
railway sections, which can usually more distance of 36 kilometres and a track type of rolling stock requiring double the
or less be calculated by means of thumb occupancy of close to 80%. Furthermore, power and operating more frequently than
rule calculation methods. However, for the succession times between trains could currently, could not function on the
moving block (e.g. ERTMS level 3) this is be decreased by up to 1:35 minutes, existing power supply. By simulating both
rather more complex. improving the overall capacity of the line. planned and disrupted 2010 operation it
Due to continuing changing could be demonstrated that the proposed
circumstances it is hard to estimate the System functionality: Robustness power supply measures could be
exact time and place of a train relative to due to constant power supply improved.
the next train, which makes a good case The power supply must support the If the substations were to be connected,
for establishing the appropriateness of a planned rail service. In the ideal situation the power spread and peak hour load
moving block signalling design by way of there will not only be sufficient supply for could be divided, in addition to saving on
simulation. Yet a signalling design acceleration after an emergency stop at a investments for additional substations on
certainly must always support and enable signal but also sufficient supply for a train line 6. Moreover, HTM was pleased by the
the timetable, as the Zaanlijn between to continue when for instance a substation reliability of the results and the insight the
Amsterdam and Den Helder in the faults. These type of power supply simulation gave into the expected energy
Netherlands demonstrates. Being a highly calculations ideally require a continuous consumption (kWh) in 2010, which HTM
occupied line, especially during peak hours simulation, solving all the equations every used to their advantage when negotiating
transporting a stream of commuters into second and using the numbers to change their contract with the power company.
Amsterdam, any train delay will snowball the state and output of the simulation in
to a major breakdown of punctuality on order to provide insight into the maximum Simulations to assess power supply
the line. possible speed due to power supply. investment proposals
In a joint effort the infrastructure Traction power supply simulations are Constant and sufficient power supply to
manager and the railway operator have based on dynamic load flow, which the trains becomes more important in
explored various scenarios to improve the requires feedback of electrical power mountainous terrain. A drop in power can
performance of the line, ranging from supplied to the mechanical performance of result in the train not being able to climb
reducing rolling stock breakdowns to the train – as it operates on the designed the hill, while generally it already requires
putting fences along the tracks against layout according to the planned timetable more power to climb that same hill than
wandering sheep. However, one of the and answering to the signals. Preferably, to run in flat countryside. Hence the
reasons the timetable was so sensitive to the simulation contains not only the benefits of successful modelling of power
disruptions was the fact that the timetable system under normal conditions but also supply can extend beyond realistic train
did not contain any margin to cushion fault conditions. timetabling to accurately predicting the
irregularities. In this way, the robustness of the new power consumption.
Simulation demonstrated that by moving operational model for the tramway lines 3 And to take it one step further, it can
signals in some locations the trains could and 6, operated by city of The Hague's even be used to accurately predict the
keep their speed longer, thus shortening public transport company HTM, could be national power infrastructure provision
>
Speed profile line 6, current situation. Speed profile line 6, future situation.
All trains in both directions are shown in the same diagram.
Traction diagram line 6, current situation. Traction diagram line 6, future situation.
Voltage level between km 8 and 9 is close to level of Connecting substations helps spread peak hour demand and
undervoltage protection of approx. 420 V, causing trams to shut increases minimal voltage to approx. 520 V (see km 8-9),
down. preventing shut down of trams. This even applies despite the
new rolling stock demanding double the power.
october 2008 | the rail engineer | 33
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