The influence of the pre-sag of a railway contact wire to the current collection performance

200km/h급 전차선로에서 사전이도가 미치는 집전성능 영향 분석연구

The railway catenary is softer in the middle of a span than at the end. This stiffness variation induce the vertical motion of a moving pantograph, which results in the large variation of contact forces. To reduce the vertical motion of a pantograph, we can introduce a pre-sag of the contact wire. The pre-sag changes merely equilibrium position of the contact wire. Because the pantograph must follow the sag added to the motion of the contact wire, the sag gives downward forces to the pantograph. If the pre-sag is proper, the variation of the vertical motion of the pantograph is reduced. However, excessive sag worses the current collection performance because the pantograph receives too large downward forces by the contact wire. The objective of the paper is to establish the theoretical basis to understand how the pre-sag affect the contact force variation and to propose the proper sag for the railway catenary for the train speed up to 200 km/h.