Open AccessInfluence of DC Stress Superimposed with High Frequency AC on Water Tree Growth in XLPE Insulation
Author(s) -
Frank Mauseth,
Sverre Hvidsten,
Hans-Helmer Sæternes,
Jørund Aakervik
Publication year - 2018
Publication title -
proceedings of the nordic insulation symposium
Language(s) - English
Resource type - Journals
ISSN - 2535-3969
DOI - 10.5324/nordis.v0i23.2455
Subject(s) - electrical treeing , materials science , voltage , electrical engineering , rogowski coil , composite material , stress (linguistics) , hvdc converter , moisture , power cable , insulation system , partial discharge , transformer , electromagnetic coil , engineering , linguistics , philosophy , layer (electronics)
Power electronics used for HVDC converters will stress cable insulation with a DC voltage with superimposed transients. The effect these transients have on the performance of the polymeric cable insulation is yet not clear. The main purpose of this work has been to investigate the effect of such transients on XLPE cable insulation when exposed to moisture. Laboratory experiments were performed on Rogowski shaped test objects with an insulation thickness of 1.3 mm. At one of the semi-conductors, 20 sodium chloride (NaCl) particles were placed in order to facilitate initiation of vented water trees. The test objects were conditioned with water at 20 °C for two months ensuring saturation of water inside the insulation system before testing.The test objects were aged with an AC voltage simulating the transients from a HVDC converter. Experiments were performed using the AC voltage with and without DC stress to investigate the influence of the DC level on the water tree growth. The ageing was done at 30 °C.Test objects were taken out and inspected for water tree growth regularly. The results show a rapid ageing caused by water treeing when exposed to the DC voltage overlaid AC voltage with a frequency of 5 kHz and a pure AC voltage stress.