The unevenness of contact wires is one of the factors that considerably influence the dynamic characteristics of current collection system. In order to analyze the influence of the contact wire unevenness on the contact force fluctuation between contact wire and pantograph, an instrument was devised to measure the unevenness of contact wires accurately and continuously. In order to reduce the measurement errors by the vertical vibration of measurement vehicles, the instrument consists of two pairs of laser sensors. This paper describes the measuring method of contact wire unevenness, reports some examples of the measurement of real wires, and proposes a method to evaluate the conditions of overhead equipment.

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