Improper Insulation Cutback On A Cold Shrink Termination



The above image; taken at a nuclear power plant in Southeast USA, shows a jagged cutback on an open-air cold shrink termination. During a cable system installation, the utility used Tangent Delta (TD), Very Low Frequency AC destructive withstand (VLF), and our Factory Grade® technology ascommissioning tests. After the electrical contractor installed temporary terminations on the cables, they conducted an initial round of testing.The TD and VLF tests indicated that everything was installed correctly and the system was free of defects. However, our Factory Grade® technology pinpointed substandard PD activity at one of the terminations at 1.3Uo. The installation crew acknowledged that the defect existed, but they dismissed this finding because the terminations were only temporary and would be replaced before energization.

At this point, the termination crew was informed about the importance of cutback issues in preparation for the installation of the permanent termination ends. After the installation, they retested the system with all three approaches. As before, the TD and VLF tests suggested that the system was in good working order, whereas our Factory Grade® technology indicated otherwise. The PD activity was located at the insulation cutback on a cold shrink termination. The installation crew linked this oversight to a combination of conditions: 1) A tool riding on the tape shield had inadvertently compromised the cutback. 2) Because it was dark during the installation, the jagged edge wasn’t noticed.

This situation has taught the utility to reconsider their testing methodology, as our Factory Grade® technology has proven to identify the workmanship errors that other testing approaches have overlooked.