A study on assessment of dropper life for conventional line speed-up

초록

In steady state, tensile load caused by contact wire dead load is applied to droppers. At the moment a train passes, the droppers are slackened by pantograph uplift force. After the train passes through, variable force is applied to the droppers and tightened again due to contact wire dead load. Increase of dynamic load is caused by pre-sag that increases the static applied to a dropper, and if dynamic load becomes too large, fatigue rupture may occur. Starting from April 2004, the 300km/h class Kyungbu High-speed Line has suffered dropper rupture at over 55 locations. Even on the express line of France, cases of dropper rupture have been reported. Accordingly, assessed in this paper is the influence of pre-sag to dropper life measured at the conventional Honam Line to increase speed and current collection performance. First, to estimate fatigue life of a dropper, a rupture mode and a P-N diagram was analyzed and obtained from a developed dropper fatigue tester. Then, the effect of the amount of pre-sag and train speed to dynamic load when a train passes was analyzed by a catenary-pantograph simulation program. Results of estimated variable force history were simplified by rainflow cycle counting. Then, dropper fatigue life was assessed by applying Miner's rule to the simplified force history and P-N diagram. The proposed dropper fatigue test method and fatigue life assessment procedures are expected to be an assessment guideline and secure safety for tension increases for speed enhancement in respect to newly developed droppers and reliability of droppers when pre-sag is applied.