Aging and related phenomena in modern electric power systems

Recent progress is reviewed on the research and development of electrical insulation applied to modern electric power systems. This paper covers several areas of insulation systems including cross-linked polyethylene cables, gas-insulated switchgears, composite insulators and oil-immersed transformers. A number of aging processes are presented and analyzed. Typical aging processes are considered to be due to tree formation, partial discharge, electrochemical processes and thermochemical processes. Almost all causes of aging have been itemized and have been phenomenologically verified. Several other theoretical aspects need to be clarified.