Eddy current inspection device for wear of overhead lines on railroads tracks

The contribution describes an innovative eddy current device for the measurement of the wear state of the overhead lines of an electrified railrods track. The inspection system is installed on an inspection train. Physically the remaining height of the line is measured. From that the resulting cross section of the line is computed. The EC-sensor is integrated in a currentless hoop over the hoop broad side, so that the wear measurement is performed independant on the transverse position relative to the track. The segmentation of the sensor strip renders possible to measure several parallel lines simultaneously. The EC-electronics is connected as well as the sensor on the high voltage level of the line and is mounted on the roof of the inspection train. Into each sensor element the superimposed currents of 3 frequencies are fed (multifrequency method). The resulting magnetic field induces in the line eddy currents whose amplitude and phase depend on the electrical and geometrical line properties (cross section, shape) and affect vice versa the impedance of the sensor element. The EC-electronics produce and process the needed signals and make available the digitized EC-data with the information about the line height. The EC-software yields the steering and controlling of the EC-hardware functions and the online processing of the EC-data. A digital algorithm based on the linear regression method gives the numerical value of the line height at the actual track position. It will be reported about applications on actrifical line models produced with different heights by a machined grinding procedure to verify the accuracy of the inspection method as well as on high speed mearurements obtained with the inspection train to study the effectiveness of the procedures to discriminate against the disturbing influences acting along the track.