From the Editor

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This issue includes three articles, the first titled “New Categories for Phase-Resolved Partial Discharge Pattern Classification,” by Contin, Piccolo, and Cavallini. It presents a refined framework for analyzing phase-resolved partial discharge (PRPD) patterns in insulation diagnostics. The study questions the traditional one-to-one link between PRPD shapes and defect types, proposing three new categories: voltage-dependent, multiple, and ambiguous patterns. This is to better represent the changing nature of discharge phenomena. By testing insulation systems rated between 4 and 18 kV, including porous tape insulation and four-layer mica tapes, the authors show how PRPD patterns develop under different voltage levels, aging conditions, and stress factors. Examples include distributed micro-void discharges that change from “rabbit-ear” to rounded shapes, symmetric in polarity and phase. The article emphasizes the limitations of relying only on pattern shape for diagnosis and recommends additional localization techniques such as antenna probes and ultrasound detectors. This work is especially valuable for those seeking to improve the reliability of insulation evaluation and develop more advanced pattern-recognition systems for rotating electrical machines.