Methods and instruments for stray current verification in DC rapid transit and railway systems

Modern electrified transportation systems feature increasing installed power and performance and correspondingly stray current phenomena and corrosion are receiving more attention in terms of contractual specifications and request of final validation of proposed solutions, as well as a maintenance program that can actively tackle stray current issues. The problem is complex for the system physical extension, difficult measurement conditions and variability of electrical parameters. This work considers validation of stray current protection performance, in terms of track voltage, track leakage and collected current, and impressed potential on structures along the right-ofway. The exemplification of the specifications of a hypothetical instrument and setup support the discussion

Impact of rail impedance intrinsic variability on railway system operation, EMC and safety

Running rails in electrified transportation systems are the interface element for several phenomena related to system performance, electromagnetic compatibility and safety: useful voltage at rolling stock, short circuit current, induced voltage, stray current, and track circuit operation. This work presents the physical and mathematical groundings of rail electrical parameters (dc and ac resistance, ac internal and external inductance) and experimental results available in the literature, discussing variability and reliability for each interface. The results consist thus of the identification of the relevant rails longitudinal electrical parameters, the presentation of a set of reliable experimental values, and the discussion of the best approach to manage their variability and uncertainty

Measurement of the Internal Impedance of traction rails at 50 Hz

The electrical behavior of sample steel traction rails is analyzed considering the resistance and the external and internal inductance. Measurements are performed on two rail arrangements at different current levels (up to nearly 2 kA) at 50 Hz and over an extended frequency range (50 Hz to 100 kHz) at low currents, so that skin effect and saturation phenomena are clearly visible. Great accordance with the results obtained using Carson's formulas is found