Moisture ingress is a life limiting factor for many assets, due to the degrading nature that water has on the performance of electrical insulators. For oil filled assets, moisture can result in degradation processes being accelerated. This ultimately results in assets being replaced sooner in their lives, or requires that maintenance activities must take place sooner.  Replacing an asset sooner in its life, results in the consumer paying more for non-load related works, while an increase in the maintenance activities increases the Whole Live Cost(WLC) of assets.

National Grid Electricity Transmission (NGET) has identified several families of bushings and Cable Sealing End (CSE) which are thought to have problems with moisture ingress. Many types of bushing and CSE use O-rings to prevent moisture ingress; however different designs appear to be more successful at keeping moisture out than others.

NGET also has evidence that moisture will naturally creep into these assets over time; based on existing data that shows a linear increase in moisture with the age of asset. As there are critical thresholds for bushings and CSEs in terms of the maximum moisture levels, understanding the performance of these seals and when these thresholds are likely to be exceeded is essential to effective condition based management of these assets.

Objectives

The objectives of the project include:

1 -  To understand the performance and degradation of O-ring seals used in transformer bushings and CSEs.
2 - Develop a synthetic test environment to test O-rings, which replicates the in-service environment.
3 - Assess the application of novel materials for use in O-ring seals for bushings and CSEs.