Polymer Flake and Degraded Paper Fiber

Transmitted Oblique Off Crossed Circular Polarized Light

This group of particles is from an oil sample collected from a 8400kVA transformer. This
transformer was reportedly gas blanketed and sealed. The redish flake on the left is the
result of the oxidation of the oil and the subsequent formation of polymer films on surfaces
in the transformer. These films shrink and crack as their carbon coordination number increases.
This happens when the surface they are in contact with becomes hot enough to suport these
reactions. The expansion and contraction of the substrate often results in the release of
fragments of this film, as seen here. There is also a degraded paper fiber in this field of
view. This paper fragment has a degree of polymerization below 200. Large numbers of these
degraded paper fibers indicates degradation of the core insulation.