Review of Insulation Ageing and Lifecycle Management for Oil‐Immersed Power Equipment: From Conventional Testing Analysis to Artificial Intelligence Method

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Oil‐immersed power equipment is a critical component for energy transmission and secure operation of modern power grids. The ageing of oil–paper insulation under combined electrical, thermal and mechanical stresses directly affects equipment lifetime and system reliability. This paper presents a comprehensive review of the ageing behaviour and full‐lifecycle management technologies of oil–paper insulation in oil‐immersed power equipment. First, the structural characteristics of oil–paper insulation and its microscopic ageing mechanisms under multi‐stress conditions are analysed. Subsequently, lifetime calculation models under electrical, thermal, and electro–thermal–mechanical coupled stresses, together with their recent application progress, are systematically summarised. Ageing condition assessment and remaining useful life prediction methods based on characteristic parameter testing and multiphysics techniques are then reviewed, followed by an overview of recent advances in ageing‐state visualisation and dynamic evolution analysis. Finally, this paper discusses artificial intelligence‐oriented intelligent operation and maintenance (O&M) systems, digital twin (DT) modelling and knowledge graph applications. Based on the review, this paper further discusses future research directions, including lifetime degradation mechanisms and dynamic prediction of oil–paper insulation under extreme operating conditions, collaborative O&M management of equipment clusters, DT‐driven proactive safety protection and full‐lifecycle O&M technologies for environmentally friendly oil‐immersed equipment. This review aims to provide a systematic theoretical basis and technical reference for full‐lifecycle management, risk early warning, and the safe and reliable operation of oil‐immersed power equipment.