Evaluation of the effect of structural defects in the heat-shrink cable terminal on electric field distribution

Abstract

Cable terminals are used for the connection of high voltage underground cables to busbars and transmission lines. Various defects may occur in cable terminals used as Heat-Shrink or Cold-Shrink. As a result of these defects, fires and long-term power outages may occur due to the breakdown of the cable terminal depending on partial discharge. Consequently, human life losses and economic losses are inevitable. In this study, a heat-shrink cable terminal with 36 kV phase-to-phase operating voltage randomly failed while measuring power quality parameters in the field is examined. In this context, it is aimed to examine the root causes of the failure in the field with the finite element method according to different design and structural defect situations. For this purpose, the cable terminal was modeled in real scale in Ansys Electronics Suite finite element software in line with the data received from the manufacturer. According to the analysis results, especially in case of peeling the entire outer semiconductor layer on the XLPE and partial peeling of the outer semiconductor layer on XLPE increases electric field significantly compared to the reference design. In addition, the thickness and relative permittivity changes of the critical elements used in the cable terminal affect the electric field distribution. According to the results of the analysis performed, the defect situations that could be the root cause of the failure was determined. Also, the effect of other defective situations was understood and reliability analysis was made.