High-Speed Railways Innovation Centre Trust

The involvement of autotransformers in a 2x25 kV traction system increases the severity of faults. Unattended faults lead to component failure, making reliability planning essential for the system. This paper proposes a method of estimating the fault current variation with fault location using a node-admittance matrix-based approach. The system is further analyzed during various contingencies to ensure a robust design, and its performance is enhanced using Static Var Compensators (SVCs). An optimal voltage compensation algorithm is proposed to trigger in the event of any outage. A comparative analysis is presented on a 30 km sample feeding section, with SVCs placed at the substation and then at the sectioning post.

The paper presents a simple approach to determine optimal substation spacing in a 2x25kV traction power supply system (TPSS). Economy, being one of the significant design parameters of TPSS, is affected by the number of traction substations (TSS) or distance between them. Hence, this paper highlights the influence of total cost incurred in TPSS due to energy losses and component installation on substation spacing. Particle swarm optimization (PSO) technique and analytical approach are used to determine the optimal spacing between substations. Individual components of the 2x25kV TPSS are modelled to perform load flow analysis using a current injection algorithm. A Python code is developed to simulate load flow and determine optimal substation spacing. Results obtained with the proposed approach align effectively with the objective of determining the optimal spacing between substations with minimized TPSS costs.

Analytical evaluation of the harmonic spectra pertaining to pulse width modulated (PWM) voltage waveforms, using double Fourier series, is a computationally intensive exercise. This paper presents simple closed-form expressions for the Fourier coefficients of output voltage in a two-level voltage source inverter operated with regular symmetrically-sampled sine-triangle PWM. The proposed approach is based on Fourier theory of jumps and doesn't involve integration. Simulation and experimental results are presented to validate the proposed analytical approach

Electrification of railway systems, increasing oper- ating speeds of trains, and introduction of high-speed trains have renewed the need for detailed study on traction power supply systems. This paper reviews two technical standards on traction supply systems, namely, EN50163 and EN50388. These standards are related to system voltage levels and power factor conditions for secure, reliable, efficient and economic operation of the entire system. Further, the paper presents detailed simulation studies on one electrical section of a 2x25 kV traction system. The catenary and feeder voltage profiles are obtained for a train positioned in the section, consuming a certain quantity of power. The relative influence of the different system parameters on the catenary voltage profile is evaluated through multiple simulation runs, considering a distinct set of parameters for each run. From the simulation runs, it is observed that traction transformer leakage reactance, catenary and rail impedances along with mutual impedances among the catenary, rail and feeder are more influential than the rest. Variation in the voltage profile with train location, power consumed and operating power factor are illustrated through the simulation studies. The worst- case operating location of the train from the point of view of catenary voltage dip is determined. The simulation studies are finally utilized to derive the limits on the maximum power that can be drawn by a single train, operating in this section, on the P-Q plane, complying with the relevant traction standards.