The role of micro-structural and mechanical properties in the framework of the model for damage inception and growth from air-filled voids in Polyethylene-based materials for HVDC cables
An innovative, physical, aging and life model for polymeric insulation systems, founded on damage inception and growth at the level of microscopic cavities, was developed previously by the authors. This paper is focused on the role played by micro-structural and mechanical properties (such as crystallinity and Young's modulus) in the framework of such model. These concepts are applied to the case of LDPE, HDPE and XLPE matrixes. The relevant estimates of damage growth rate and time-to-failure as a function of void size and applied electric field in typical working conditions for HVDC power cables are performed. The results show that, under the assumptions made, the crystallinity level itsel…
Wireless partial discharge tracking on cross-linked polyethylene MV and HV cables
Medium voltage (MV)/high voltage (HV) cable lines are high-value assets and require substantial costs for their installation or replacement. For this reason, the capability to assess the condition of cable lengths and accessories on site is of great importance. Cross-linked polyethylene (XLPE) insulation is extensively used for MV, HV, and extra-high voltage (EHV) class cables [1] thanks to its excellent voltage-endurance and thermomechanical properties. In particular, XLPE-insulated cables feature substantially lower losses, easier manufacturing and jointing procedures, better environmental compatibility, and higher operating temperature compared with impregnated paper cables, which lead t…
Critical issues in the PD testing methodology for XLPE-insulated MV cables: An experimental case
This paper describes some critical issues arising during the partial discharge (PD) testing of a 500m delivery length of an XLPE-insulated MV cable. At first, conventional PD measurements were performed on the whole length by using a standard acquisition system; PDs activity was detected, but the system allowed the operator to localize the PDs only on a length of 70 m. A visual inspection of this section highlighted the presence of an excoriation in the outer sheet. Aiming at a more accurate pin-pointing of the defect, more measurements were carried out in the proximity of the outer defect using a portable PD detection system. These measurements showed PDs activity, whose source was located…