Space charge accumulation in XLPE versus temperature and water content
DOI:
https://doi.org/10.5324/nordis.v0i23.2447Keywords:
HVDC, space charge, water, temperatureAbstract
The rate of accumulation and amount of space charge is dependent on several factors, including the electrical properties of the insulation material and the temperature of the insulation. Increased water content has been found to increase the conductivity of XLPE up to three times compared to that of dry XLPE, and is therefore also expected to affect space charge accumulation.
This paper presents results of space charge measurements on dry and wet 0.3 mm thick XLPE insulation at 20, 40 and 60 °C. The applied voltage was 10 kV, and the measurement period 14 days. Results show that increased water content leads to the formation of heterocharge at the cathode at 20 °C, as opposed to homocharge in case of a dry sample. At higher temperatures, increased water content mainly decreased the magnitude of accumulated charge.
A conductivity-based sectioned model was introduced, and was used to recreate the changes in electric field set up by the accumulated space charge. Comparing the model with the measurements showed that conductivitybased charging was a central mechanism in space charge build-up. At higher temperatures, additional effects not covered by the model were present.
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