Cable Design
Ablation between Metal Sheath and Buffer Layer of High Voltage XLPE Insulated Power Cable
Eifelkabel has helped to develop a test method and a design that does not show this problem.
The corrugation aluminium is a common sheath structure of high voltage cross-linked polyethylene (XLPE) insulated cable due to its good bending performance. However, some problems, especially buffer layer ablation, have occurred frequently in cables due to such corrugated structure. Some further studies are carried out around the ablation morphology. The morphology of the ablated buffer layer from laboratory is observed by optical-microscopic, which shows great similarity with the ablation points in failure cables, verifying discharge is one of the causes of ablation.
Corrosion
Eifelkabel is member of Cigre working group D1/B1.75 about Corrosion
Corrosion is a major concern for sub-sea cable reliability. These cables are normally watertight, however, CIGRE recently recommended to test wet sub-sea array cables for offshore wind-parks. Furthermore, it should be noted that several kilometres of wet medium voltage submarine cables were installed more than twenty years ago and have been operating without any reported problems.
For example, stress introduced electrical degradation (SIED) of the inner semi-conductive screen is influenced by the polymer properties.
Many tapes contain additives such as super-absorbent polymers (SAP) that do not work in salt water and degrade very quickly without any saltwater absorption. A newly developed SAP has been tested for this application.
WTR testing
Even if water-treeing in modern cable is less a concern than during the 70ies. The bad experience during that time should not be repeated. Therefore in certain countries strict requirements are imposed doing a so-called “long term wet ageing test“.
The VDE requirements isthe most famous.
Eifelkabel has assisted in several tests passing TB 722 for 66 kV cables and passing the requirements of VDE 0276-620.
He was member of Cigre B1-55, ex-chair of ICC A06D and A13W.
He is also secretary of Cigre B1-92 (lead free cables)