SimuX

• Train performance under operating conditions
• Dimensioning of the traction power system
• Adequacy of the traction system, feeder cables and catenary / third rail
• Maximum, minimum and average voltage at a train’s pantograph
• Rail potential and stray current
• Energy consumption and losses
• Energy saving strategies, tested before they are applied
• The effect of regenerative braking and the line’s receptivity and recuperation ratios
• The effect of different feeding schemes
• Short-circuit currents

The software takes many variables into its model to bring results close to real operating conditions. The main inputs are:

• Names, lengths and numbers of lines; passenger stations with minimum and maximum dwell times (random or fixed)
• Curves, gradients, speed limits and maximum operating speed
• Data on the depots connected to the lines
• Operation rules: cars per train, headways, departure and arrival points, skip-stop stations
• Number, location and naming of substations, their equipment data, isolating sections, catenary / third-rail data and the rail potential control device
• Vehicle data: maximum speed, empty/full weight, maximum acceleration, braking and jerk, tractive effort–speed and braking effort–speed diagrams

Unlike most competing products, SimuX’s dynamic algorithms model the interaction between trains and the power system at every time step, as conditions change along the alignment. Voltage at the train affects its performance: when the voltage falls, the acceleration, speed and position of the train change. The power drawn by the train falls and the power system partly recovers from the sag. SimuX models this non-linear control function for both motoring and regenerative braking.

The mean useful voltage required by EN 50388 for mainline railways can be calculated with SimuX. Thanks to its modelling of current and power limitation at low voltage and of voltage limiting devices (VLD) on the return circuit, SimuX finds the achievable headway even in worst cases such as two neighbouring substations out of service.

SimuX analyses the impact of train bunching and whether the power supply can support several “stacked” trains restarting at once. Because many train types and compositions can share one model, it supports integrated operating plans; and because passenger load can differ between stations, systems are dimensioned more realistically.

With on-board energy storage systems (ESS) and catenary-free zones in the simulation, the ESS can be dimensioned and the charging times in the designated areas optimized. Depending on the project, the iteration time can be 100 milliseconds or less, so that critical values such as rail voltage are fully checked against the standards.

In historic and touristic areas a single contact wire often makes buried reinforcing feeder cables necessary in tram projects. SimuX models these cables and their connection points to the contact wire separately, to optimize cable size and connection frequency. Cables parallel to the running rail can also be modelled to reduce rail voltage. Options like these prevent over-sizing and keep simulation-based investment decisions accurate.

The software has been used successfully in many projects, both for lines under construction and for testing lines in service against new conditions, and its results have been confirmed to be very close to real values.

The first version of SimuX was developed in 2003; it builds on a 25 kV AC simulation program written as an MSc thesis in 1994. See our history.