Defect Blog

Each year, millions of people and thousands of businesses are impacted by underground cable system failures. IMCORP is dedicated to advancing the understanding of how these failures occur and more importantly, how they can be avoided.

Mar 23 2012

Improper Heat Shrink Application


Posted in: Workmanship, Wind, Generation


These images show the development of a medium voltage cable failure in an open-air heat shrink termination. The first image (left) shows the IEEE 48 non-compliant heat shrink at the termination that was located by the IMCORP's Factory Grade® technology that was recommended for repair. The cable system owner opted to forgo the repair, choosing to trust the results of a subsequent passing voltage withstand test. The cable was put back into service and failed four months later at the defective termination point.

The second image (right) shows the cable system after the PD activity resulted in failure.  During installation, the improper positioning and insufficient shrinkage of the layers  resulted in a interfacial voids and a gap between the cable semicon cutback and the termination stress control tube.  The semicon cutback area is the most critical part of a termination. This particular situation highlights IMCORP's ability to find defects long before they progress to the point of complete failure. It's worth noting that this is one of many examples where legacy test have failed to indicate an issue that IMCORP's Factory Grade® technology correctly identified.