During service, overhead transmission line insulators lose their functionality due to electrical stresses and environmental conditions causing incessant flow of leakage current (LC) on their surface thereby leading to insulator ageing. Ceramic glass insulators are the oldest and the most used type of insulator, some operating for decades and approaching the end of their projected life span. A technique to assess as well as diagnose ageing glass insulators has yet to be proposed. This book, therefore reports a new method of assessing the surface condition of ageing transmission line...