Outdoor high voltage polymeric insulators

Composite polymeric insulators are increasingly being accepted by the traditionally cautious electric utilities worldwide. They currently represent about 70% of installed new high voltage insulators in North America. The tremendous growth in the applications of non-ceramic insulators is due to their advantages over the traditional ceramic and glass insulators. However, because polymeric insulators are relatively new the expected lifetime is not known and is of critical interest to the users. In this paper a review is presented of the recent performance experience of high voltage composite polymeric insulators in outdoor service, testing methods, the ranking of the materials, the 'role' of the fillers, the role of the low molecular weight components present in the most widely used insulator types, the mechanisms responsible for the loss and recovery of one of the most important properties of polymers (the hydrophobicity), various methods to optimize the electrical performance and a relatively new method for evaluating polymeric systems in the field.