Simulator for studying operational and power-supply conditions in rapid-transit railways

The paper describes the development of a computer-based simulator which may be used to study the relationships between train movements and power-supply conditions in a 2-road rapid-transit railway. The work was specifically undertaken to enumerate the energy saving consequent on the introduction of chopper-controlled traction-control equipment with regenerative-braking capability. In the simulator, track topology and signalling constraints are represented by a sequential block structure which is analogous to the fixed-block signalling arrangements. Tractive characteristics of the traction equipment are represented by models which are train speed and line voltage dependent. Powering and braking trains are represented by piecewise linearised models and a complete power-network solution is obtained at each update period. The simulator is written in extended Fortran IV and is reasonably efficient in computer processing time; e.g. running a 1 h service at 90 s headway on a 5 km section of track typically requires 4 min of central processor time on an ICL 1906A. Simulating 20 km of double track, with up to 100 trains per track, typically requires 36 Kwds of core. Although the simulator was developed specifically for energy-consumption calculations, the methods of representation are quite general. The simulator may thus be used to study other problems of interest in train performance and signalling studies.