Damaged Semicon at Termination at a Wind Farm
While commission testing a renewable energy generation site, IMCORP’s Factory Grade® assessment found partial discharge(PD) activity near a T-body termination. Visual inspection of the termination showed no indication of a problem. The termination was decontaminated, void filling grease was reapplied, and the cable was retested. The test detected the same PD activity. The cable was reterminated with a new T-body, however the PD results were the same as before. The crew finally cut off a 20 foot section of cable and spliced in a new section and termination. Upon retesting, the cable was found to meet the manufacturers’ standards. The defect was discovered to be a small protrusion through the outer semiconductive layer about 6 inches below the semicon cut-back.
It’s important to note that the magnitude of signal from the partial discharge activity in this defect was extremely small – only 5pC. Less sensitive tests would not have been able to detect the existence of this defect, though it clearly is an issue that would impact the performance of the cable system.