With the increment of passenger railway traffic especially in high speed lines, improvements in railway transportation safety become even more crucial. This paper presents technological and commercial trends in this area, enumerates innovative on-going related projects and proposes the application of new wireless communication standards such as, DSRC -WAVE (Dedicated Short Range Communications and Wireless Access in Vehicular Environment) or 802.11p; 802.16 or WiMAX; and MBWA (Mobile Broadband Wireless Access) or 802.20, in train control communications networks. In order to validate this proposal, we have designed a model for a wireless communication system deployed in a fully redundant configuration. The application of these new open-standard technologies will allow an affordable deployment, ubiquitous, always-on and interoperable muti-vendor mobile broadband train control communication system that supports new safety services and applications. Railway, signaling, wireless, 802.11b/g, MBWA

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A rapid voltage change (RVC) is a type of power quality disturbance that has not received sufficient attention in the international power quality standards. At present, IEC 61000-4-30, Ed. 3, defines a precise method for RVC detection and analysis. RVCs can cause or contribute to flicker. However, the existing studies on the subject have not found a correlation between the short-term flicker severity index, Pst, and the parameters of a RVC event. This paper provides an interpretation of this lack of correlation and shows that instead there is a correlation of RVC events with the instantaneous flicker sensation, P inst . The work is based on the analysis of both simulated waveforms containing RVCs and waveforms recorded in low-voltage and medium-voltage locations.

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