This book is on modern electrical insulation. The insulator is backbone of any transmission/ distribution system. In the past, ceramic insulator have been used since 1880. But sine last three decades people are now using polymeric insulators which are better than ceramics in many respects like, light weight, easy to install, better pollution performance and more aesthetic. These insulators are made of silicon insulator rubber and thermoplastic elastomers. These materials are partially organic and partially inorganic. Due to organic nature, these degrade with the time due to environmental parameters like UV radiation, humidity , temperature and other environmental parameters. Due to which, it becomes necessary to access their performance in any environment before use.