PSNet,
There is an interesting article in the current issue of the IEEE
Transactions on Dielectrics and Electrical Insulation - Vol 7, No 5, Oct
2000
Degradation of Insulating Materials under Electrical Stress
by C. Mayoux
Laboratoire de Génie Electrique
Université Paul Sabatier/ CNRS
Toulouse Cedex France
ABSTRACT
An avalanche of physical and physicochemical phenomena, often
self-sustained, leads to the end of life of an insulating material. The
collapse of the insulating role of a material is mostly due to the
electrical field stress, The path leading from the catastrophic situation,
the breakdown, back to its origin is followed in the present paper. A
defect, pre-existing or created by the in-service stresses, gives rise to an
ionization process in a volume bounded by insulating walls. With time the
process does not remain identical due to both changes in the material and
gas evolution, which makes it difficult to interpret the detected electrical
signal. The end of life will occur through microcracks in which new
discharges are initiated, activating the propagation of these structural
failures. This change of structure of the insulating material when due to
the existence of water molecules will lead to the same kind of final
degradation. The polymeric insulating materials could contain additives but
they lead only to a partial healing. From polymers as little complex as the
PE used in cables, assuming that there is no pre-existing defect, one
endeavors to understand how a microstructure reacts with a local field or
accumulated charges. The present paper summarizes the thoughts of the author
pertaining to the problems of aging and dielectric breakdown in organic
insulating materials, processes often given a concrete form through
experiments.
- - - - -
The author thoughtfully combines his own experimental results by comparing
it with other papers. He provides insight into the mechanism of failure -
which seems to be generally applicable to any insulation system. Certainly
the continuing pressure to cram more electronics into smaller spaces will
push against the physical limitations of insulations. This paper will keep
the focus of failures on basic mechanisms within the materials. Enjoy...
As before, I am not a lending library nor source for the entire article.
You will have to get it thru normal technical library means.
br, Pete
Peter E Perkins, PE
Principal Product Safety Consultant
Tigard, ORe 97281-3427
503/452-1201 fone/fax
[email protected]
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