Qualification tests performed on composite insulators for 132-150 kV overhead lines

Composite insulators may be prone in service to damage of the external housing (tracking, split, erosion, chalking) and of the core (mechanical failure). An IEC Standard was issued that ENEL applied, with some adaptation and implementation, in performing the insulator qualification. As for a tracking and erosion test, two alternative procedures are given by the IEC Standard to reproduce the service stresses in severe ambients. To cover the risk of fractures in service due to fatigue and stress corrosion of the insulator core, ENEL studied and defined a mechanical-chemical long term test. The authors describe the results of the above mentioned tests obtained on a few types of composite insulators of the latest production. For the two insulator types that have now passed all the planned tests, a pilot service experience is going to start on 132-150 kV line sections chosen all over Italy