Overhead Electrification Line Inspection

Railroad companies are required to inspect tracks, rails and electrical systems on a regular basis. Laser sensors and laser scanners are frequently used for these purposes because they are non-contact, high accuracy and high speed. Laser measuring devices can collect rail geometry information at fast traveling speeds. In a recent application, one railroad inspection system integrator selected the Acuity laser line scanner to detect and measure the position of overhead electrification lines.

The configurations of the catenary ines that supply the power to electric locomotives tend to vary from country to country. In the Northeast United States, a 3-wire configuration is used. The lines may be suspended 0.5 - 4 meters above the top of the inspection car and the cable diameter is typically 10-20 mm. As this is a friction surface, it is often shiny.

This is a challenging application because the optical scanner is positioned to scan towards the sky. Although the system is equipped with an optical bandpass filter for ambient light reduction, direct sunlight can temporarily "blind" the avalanche photodiode inside the AR4000 laser rangefinder. The sensor recovers within two sample periods. To minimize the effects of direct sunlight or its reflections, Acuity suggests installing fan-shaped blinders which narrows the scanner's field of view to just the area of interest. This component should be painted flat black to minimize reflections.

The suggested configuration of the Acuity line scanner should include the AR400-LIR laser rangefinder with a 20 mW laser diode upgrade, an optical bandpass filter, Close Focus Optics set to the minimum and maximum ranges of the line position, a 200 KHz PCI High Speed Interface Card, the line scanner iteslf, 7m cable extensions, an AC power supply and optionally, an environmental enclosure. For more information, contact Acuity sales engineers.