An adaptive affinity propagation clustering（adAP） algorithm is proposed for pattern recognition of UHF signals from four insulation defects induced partial discharges in GIS.The adAP algorithm searches the number of clusters for finding the optimal clustering solution by adaptive scanning of parameters space

and adaptively adjusts damping factors to eliminate oscillations and adaptively escape from oscillations when the damping adjustment technique fails

thus overcomes two corresponding limitations of the conventional affinity propagation clustering（AP） algorithm.In addition

the clustering results of the proposed adAP algorithm is verified by several clustering validity indexes

indicating its accuracy in the number of clusters and in the classification of different types of defects

and showing better performances in processing time and cycle number than the conventional AP algorithm.