Partial discharge classification and diagnosis of power cable joint by statistical processing

The prefabricated type used generally in Korea to join cable runs on new installations, because installation is very simple and save time. This type is a permanent, shielded and submersible cable joint for direct burial or vault application. It confirms to the requirements of IEEE std. 404-2004 by factory testing, but many problems of insulated cable systems are caused by internal defects of the joint part which have to be mounted onsite. Faults arise from impurities or voids. A suitable solution for a monitoring of cable joints during the after-laying test and service is partial discharge detection. This paper described the influence on partial discharge distribution of various defects at the model power cable joints interface by statistical processing. As the result of analyzing Phi-q-n patterns, several parameters i. e. maximum discharge qmax, average discharge q and average angle of discharge thetasg were found to depend upon the defect type varying applied voltage. As the result of analyzing discharge number distribution of Phi-n cluster using K-means clustering, clusters shifted to 0deg and 180deg with increasing applying voltage. It was confirmed that discharge quantity and Euclidean distance between centroids were increased with applying voltage from the analyzing centroid distribution of Phi-q cluster.