By Cassiano Lobo Pires What the IEC Tells Us About Stray Currents ©ISTOCKPHOTO.COM/WONRY Guidance for a practical approach. T IS WELL KNOWN THAT IN DC-ELECTRIFIED RAIL LINES, THE running rails are used to return the traction current to the rectifier substations. However, we cannot avoid some part of this current leaving the rails and instead passing through the earth to rejoin the return circuit at a point that is closer to the rectifier substation, and so the current reaching the negative busbar of the rectifier substation. These leakages, called stray currents, seek the least-resistant paths and, in particular, piping and cable systems of any kind placed in the neighborhood of tracks. Thus, a stray current is the part of a current caused by a dc traction system that follows paths I Digital Object Identifier 10.1109/MELE.2016.2584961 Date of publication: 2 September 2016 2325-5987/16©2016IEEE IEEE Electrific ation Magazine / S EP T EM BE R 2 0 1 6 23http://www.ISTOCKPHOTO.COM/WONRY