12. Wear measuring apparatus for overhead conductor rail using light sectioning

Overhead conductor rail that employs rail-shaped conductors or deformed contact wires in confined spaces such as subways and narrow tunnels is subject to wear, yet the width of the contact surface does not change. For this reason, the standard approach used on overhead contact wires, which involves estimating wear depth based on the width of the contact surface, is unsuitable and manual fixed-point inspection is used instead.

Our apparatus uses contactless light-sectioning, via a slit laser and camera, to provide continuous contour measurements that can be used to evaluate wear depth on overhead conductor rail (see Figure 1). By overlaying the contour generated via light-sectioning onto the original profile of the rigid conductor equipment, the system measures the residual height of the conductor, and by extension the wear depth (see Figure 2). It can be used on conductors of all types and profiles. Stationary tests show that the system is accurate to within 0.5 mm irrespective of the type or profile of overhead conductor rail under measurement (see Figure 3).

The existing process for checking wear depth involves a maintenance worker conducting a preliminary inspection of high-wear sites for evidence of wear, then following up with manual measurement if necessary. Our system, which is installed on a maintenance car or similar and takes continuous measurements at 20-mm intervals at a speed of 30 km/h, is both more reliable and more efficient than the current approach. The system has already been adopted by the Tokyo Metropolitan Government Bureau of Transportation for use in measuring wear on rail-shaped conductors as part of maintenance operations on the Oedo subway line (see Figure 4).