Interference of railway 25 kV AC traction power systems, and, Use of optical sensors for train detection

25 kV traction power systems present a very adverse electromagnetic interference (EMI) environment for trackside signalling cables and equipment. Methods of predicting and mitigating EMI imposed by 25 kV traction current on signalling cables are investigated and a case study based on the EMI problems encountered by the West Rail of Hong Kong upon its commissioning in 2003 is presented. Residual issues from this case study suggest the pressing need for a more innovative means of train detection to achieve full immunization from EMI.; Building on achievements of previous research works, an assessment has been made to confirm the feasibility of using Fibre Bragg Grating (FBG) sensors to replace the conventional axle counter equipment. This study describes the product development process and its plan, including the essential aspects such as reliability, availability, maintainability and safety (RAMS) requirements, functional specification, application development and safety case preparation. Preliminary design and hardware and software development have also been covered. The findings of the assessment show that the FBG sensors are able to better satisfy the functional, non-functional, interface and applications requirements of a traditional axle counter system, because of their total immunity to EMI, compactness and absence of trackside electronics. A development programme is also progressing to target for launching an on-site trial of FBG-based train detection system in early 2007.; This study is a timely and appropriate combination of academic research and practical applications in railway engineering. The outcome is an innovative train detection system with tremendous practical values.