The "hard-spot" of catenary is an intrinsic structural defect, and it is also an important index for evaluating the performance of pantograph-catenary current collection. In the traditional method, whether the parameters of "hard-spot" are transfinite only depends on the maximum acceleration in each space, which often results into incorrect judgment. First, the fuzzy c-means (FCM) is adopted to analyze and excavate the data of pantograph-catenary current collection parameters of train-set, and

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... xtract the threshold of "hard-spot" in the paper. Then, the reasonable performance index of pantograph-catenary current collection and the evaluation criterion based on three thresholds of "hard-spot" are presented. This criterion fully covers three feature parameters of "hard-spot" in order to avoid the defects with only one index for the transfinite judgment. Experimental result shows that the criterion is reasonable and effective based on the comparison between the sampled data the cluster results.