Recognition of multiple partial discharge (PD) sources in high voltage equipment has been a challenging task until now. The work reported here, aims to recognize multiple PD sources in oil-impregnated paper using Cluster Analysis (CA) and Fuzzy Logic (FL). The typical sources of PD in transformer are identified and the corresponding single source PD defect laboratory models are fabricated. From the measured PD signals, the necessary statistical parameters are extracted by applying CA for classification. A Fuzzy based algorithm has been developed to recognize single source PDs. The developed algorithm has also been applied to recognize multiple PD sources

Slivers are a common defect observed in rolled steel products such as plates and strips. This is one of the causes of rejection for applications requiring good surface finish. Typically, slivers are categorized into nonmetallic inclusion based and iron oxide (FeO) based, but their origin could be many. Unlike slivers originating from nonmetallic inclusions, analysis of FeO-type slivers is often not conclusive on the source or origin. Proper inspection and conditioning processes of slab surface before rolling can ensure good surface quality. Based on inspection results and metallographic analysis of downgraded rolled products, it was found in the present study that the majority of the slivers were FeO related. To minimize downgrading at coil stage or reduce salvaging activity, identification of the causes of FeO-type slivers became necessary. A systematic study was undertaken to establish a link between various slab surface defects leading to FeO-type slivers in hot rolled coils. Weld marking near the defects in slabs proved to be a novel technique to verify and confirm slab defect and its manifestation into hot rolled coils. Based on the appearance of slivers and severity, visual standards were developed illustrating characteristics and severities of slab defects, and the slab surface conditioning norms. The visual standard became useful in making decisions on the conditioning need of the slab and timely feedback to the upstream process. The paper describes in detail the methodology and approach adopted for this study.

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