Among the variety of problems encountered in transmission lines, the outer jacket degradation-derived faults of communication cables in railway applications have a significant impact on the transmission line parameters, especially if the cables are exposed to extremely varying environmental conditions, such as temperature deviation and humidity changes. In this paper, an advanced model of a twisted pair communication cable is proposed, together with approximated degradation functions for distributed parameters of the model, such as the shielding inductance, resistance, and capacitance per meter of cable length. This allows for gathering the distributed parameters for the proposed model under specific environmental conditions. The degradation functions for the parameters have been identified and compared with simulation results, including the communication speed and frequency band, and it has been confirmed that the transmission reliability depends on the cable condition. The authors discuss the influence of outer jacket degradation on signal behavior in terms of time and frequency domains that should be considered while developing new signaling devices for railway transportation.

Among a variety of problems with communication lines, the faults of surge protection modules in railway applications have a significant impact on the transmission line availability, especially if the devices are located in lightning-prone areas or other high-energy exposure areas, such as voltages or current changes. An advanced optimization of the surge protection module is proposed together with its verification, based on simulated waveforms for components and their limitations (e.g., power, peak power, maximum voltages, maximum currents, etc.). It allows for gathering information about the safety margin for each parameter of the components. This can be used to manage the probability of damage to the protection module. The authors have shown the power distribution during exposure that should be considered while developing new devices for railway transportation industry.