Performance characteristics of water blocking tapes and their influence on water treeing in XLPE insulation

The performance characteristics of several commercially available water swellable tapes have been evaluated in terms of their swelling behavior, water blocking capacity and influence on water treeing in power cable insulated with cross-linked polyethylene (XLPE). The nonconducting water blocking tapes have been found to exhibit superior swelling behavior and water penetration resistance than the semiconducting tapes, both in single sheet and model cable tests. Accelerated water treeing tests on miniature cables have also shown that none of the water blocking tapes had an adverse effect on insulation performance, in terms of percentage retention of breakdown strength and water tree growth rate. This evaluation has permitted the screening and selection of water blocking tapes with optimum electrical and water barrier characteristics for use in underground distribution cables. The results have been confirmed by full-size cable testing