German rail company Deutsche Bahn has fully electrified its railways using a 16.7-Hz system. The power to the system is supplied by a transmission system operated by its subsidiary, DB Energieversorgung. The system consists of 7800 km (4847 miles) of double-circuit, single-phase 110-kV lines. These unique-looking structures are easy to distinguish with a single crossarm carrying four conductors.

Some sections of this transmission network are in areas that experience severe icing. Such an event occurred in December 2004 on the transmission line that supplies power for the trains that run from Munich to Stuttgart. The transmission line was taken out of service for several days for ice removal, causing major complications in the electric service. Consequently, Deutsche Bahn contacted German engineering company Monitec to provide a CAT-1 transmission line monitoring system with ice warning software for immediate trial installation. The system was delivered within three weeks of the request, but weather conditions in the area delayed installation until Feb. 10, 2005.

The new monitoring system provides early and reliable detection of ice loads. It measures the mechanical tension and ambient temperature, and transmits that data to Deutsche Bahn's main dispatch center in Frankfurt/Main. When icing begins, the dispatch center switches off other transmission lines, which increases the temperature and causes the ice to melt.

Deutsche Bahn is analyzing the recorded data this spring. The company stated that if it deems the results satisfactory, it will install more of the early-warning systems.

CAT-1 transmission line monitoring systems are produced by The Valley Group Inc. (Ridgefield, Connecticut, U.S.; www.cat-1.com). Several hundred of them are installed in 16 countries, mainly for real-time thermal-line-rating purposes. But these systems are also extremely sensitive ice detectors, detecting ice even before it becomes visible on the lines. The system software can then calculate the icing rate and determine the amount of line current required to stop ice accumulation.