Analysis of EM coupling from AC electrified railway to nearby earth return circuit

An electrified railway is an electromagnetically complex installation due to its physical size, the interaction between its constitute parts and the electromagnetic interference coupling mechanisms between these parts. The complexity of the installation requires proper management and understanding of the electromagnetic disturbance that may compromise the safety and operational integrity of the railway infrastructure. Increasingly, over riding safety requirements demand an analysis of all credible failures, due to electromagnetic interference, under normal or abnormal operation. Such analysis lends itself to the application of analytical methods to support the measurement efforts. This work reviews the physics of the electromagnetic coupling between an AC electrified railway and nearby earth return circuits. It covers the application of transmission line theory to describe the conductive and inductive coupling mechanism that exist between railway traction and nearby buried signaling conductors.