Most existing tunnels with a small section of narrow-gauge line are equipped with a special catenary system, which is inferior in current-collection performance and requires much maintenance and represents a bottleneck that demands constant attention. Meanwhile, rigid conductor lines are now being watched as a new in-tunnel conductor system because of their high reliability and manpower-saving maintainability.

To introduce rigid conductor lines into tunnels, a transition section to/from the catenary system needs to be installed at the exit/entrance of tunnel. However, the present structure of the transition section is complicated, causing vibration, pantograph contact loss and conductor line member fatigue. It also increases the costs of construction as it involves use of many supports.

A new structure for the transition section between the rigid conductor line and the catenary system was devised and its running tests were implemented on the current-collection test machine. In contrast to the conventional structure that overlaps the catenary system and the rigid conductor line in the transition section, the new structure integrates the two to become the overall structure, thereby reducing the length of the transition section from 30 m to about 10 m (Fig. 1). This structure suppresses the contact loss time and trolley wire strain to the standard values of 20 ms and 500 μ respectively (Fig. 2). The new structure can therefore be put to practical use on commercial lines where the maximum train speed is 130 km/h.