partial discharge erosion of grading/semicon interface on hv motor
partial discharge erosion of grading/semicon interface on hv motor
(OP)
We have a 13.2kv motor in the shop. Visual inspection shows apparent partial discharge degradation at the overlap/boundary between the semi-con tape and the grading paint about 1" outside the slot. It appears this created a band which electrically isolates the grading from the semi-con.
Questions:
#1 - Is there easy repair available for this condition.
#2 - Is this condition highly destructive? From my perspective it defeats the purpose of the grading paint (to eliminate stress concentration at the end of the semi-con). But I have heard/read that others consider it to be a relatively insignificant problem.
Questions:
#1 - Is there easy repair available for this condition.
#2 - Is this condition highly destructive? From my perspective it defeats the purpose of the grading paint (to eliminate stress concentration at the end of the semi-con). But I have heard/read that others consider it to be a relatively insignificant problem.





RE: partial discharge erosion of grading/semicon interface on hv motor
Easy repair, well...
Clean up the area and re-paint with grading paint
or
Clean up the area, retape with semi-con tape and re paint with grading paint.
Corona discharge can be distructive but in most cases it is not. The idea with any repair of this nature is to relieve the electrical stress in that area.
RE: partial discharge erosion of grading/semicon interface on hv motor
An interesting website: http://www.infraspection.com/thermography/corona.html
RE: partial discharge erosion of grading/semicon interface on hv motor
So I would be inclined to think that silicon would not help, but reapplying grading and/or semi-con as suggested by Doug would help. Unfortunately there is a thick build of resin over the top of these stress control coatings (burnt away by pd in places), so it will be difficult to ensure good contact of the repair coating with the original coatings.