PSNet
As we push materials closer to their limits of performance, we need to
understand the factors influencing this performance. Here is an article that
relates electrical treeing to mechanical properties of the material. Poke it
away somewhere in the dark reaches of your mind then drag it out when your have
some unexplained insulation failure that you are chasing... Or maybe this will
be useful in setting limits of performance for insulations and insulating
systems as we go along...
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Mechanical Aspects of Electrical Treeing in Solid Insulation by BR Varlow and DW
Auckland, Univ. of Manchester, UK in the IEEE Electrical Insulation Magazine,
March/April 1996 - Vol. 12, No 2.
Key words: Mechanical stress, electromechanical, degradation, treeing,
barrier material, plasticizer effect.
Mechanical effects dominate the new theory, with the build-up of strain,
fatigue failures and fracture due to shockwaves being involved.
Main headings: Introduction, Plasticization effects on mechanical and
electrical characteristics, The introduction of barriers, Correlating mechanical
and electrical treeing characteristics at elevated temperature, and Conclusions.
References are included.
From the conclusions:
In homogenous resin, the tensile strength, modulus of elasticity and
fracture toughness all show a pronounced decrease in value as the temperature is
increased. The material's resistance to crack propagation therefore becomes
lower with the application of heat. The main reason for the degradation in
mechanical properties is that the material passes through its glass transition
point with the range of test temperatures. The treeing resistance displays a
similar fall as the temperature exceeds this critical value.
The effect of elevated temperatures on composite insulation is complex.
Not only do the mechanical properties of the resin matrix degrade as the
temperature is raised but so does the mechanical strength of the reinforcement,
and the quality of its adhesive bond with the surrounding matrix, and the
mechanical strain in the vicinity of the interface between the two components;
all factors that influence tree growth.
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any comments or feedback???
:>) br, Pete Perkins
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Peter E Perkins, PE
Principal Product Safety Consultant
Tigard, ORe 97281-3427
503/452-1201 phone/fax
[email protected] email
visit our home page:
http://ourworld.compuserve.com/homepages/peperkins
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