New Insulating Materials for Next Generation of HVDC Cables - Methods for Evaluation of Degradation Phenomena by Electrical Treeing

The ongoing in Sweden research activities aim to elaborate new material concepts that can be applicable in designing and manufacturing high voltage direct current (HVDC) cables for very high voltage levels, up to 800 kV. This task focuses on investigating possibilities provided by use of materials containing nanofillers and voltage stabilizers. Variations in breakdown strength, electrical conductivity and control of space charges with temperature and composition as well as their stability during long-term operation are investigated. This paper describes a part of the work that concentrates on elaborating a robust methodology for testing material resistance to electrical tree inception. It is argued that AC treeing test under ramped voltage may effectively be used for screening candidate materials for applications in HVDC cable insulation