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Failure modes of polyester glass insulators-surface tracking

Failure modes of polyester glass insulators-surface tracking

Failure modes of polyester glass insulators-surface tracking

(OP)
I have a failure of insulation between busbars (415V 3 phase, 150mm separation) supported on edge of glass mat re-inforced polyester sheet insulation (20mm thick). Laminate should be dry but may have intermittent condensation and located at coast but inside cabinet, inside building. About 15 years service before tracking failure. Laminate discolored.  Appeared hygroscopic.  Has anyone experience of similar?  I believe it may be hygroscopic breakdown products of polyester or initial uncured resin giving conductive solution on the cut surface (like blistering in GRP boats).  Could just be salt deposition or biological growth.  Bits have been thrown out so test not possible.  Intend to replace with epoxy-glass laminate.  Is this a good idea?

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