Effects of temperature gradient on space charge accumulation at applied voltage reversal in LDPE film

One of the main issues that affect the development of high-voltage direct-current (HVDC) cable insulation is the accumulation of space charge. The load operation of an HVDC cable leads to the formation of a radially distributed temperature gradient (TG) across the insulation. In this study, the space charge accumulation in a cross-linked polyethylene (XLPE) cable is measured under a DC electric field and TG using the pulsed electro-acoustic (PEA) method, and the effect of the TG on the space charge behavior is investigated. In addition, the bipolar charge transport (BCT) model and the conductivity model based on an improved cylindrical geometry are used to simulate the charge behavior in the HVDC XLPE cable under TG, and the experimental and simulated results are compared. The results show that the higher temperature of the cable conductor promotes the accumulation of homocharge near the side of high temperature. Additionally, with the increase of the TG, not only does more heterocharge accumulates adjacent to the side of low temperature, but more space charge also extends into the bulk of the cable insulation. More attention should be paid to the conductor shield layer and the insulation shield layer in HVDC cables. Moreover, the BCT model can more accurately describe the experimental results than the conductivity model.

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Study of Space Charge Accumulation Property in Polyethylene under Applied Voltage of Square Wave

2019 2nd International Conference on Electrical Materials and Power Equipment (ICEMPE) ◽

10.1109/icempe.2019.8727352 ◽

2019 ◽

Author(s):

Xia Wang ◽

Zi-Hang Shu ◽

Shen-jie Duan ◽

Hua-nan Wang ◽

Shuai Liu

Keyword(s):

Space Charge ◽

Applied Voltage ◽

Charge Accumulation ◽

Square Wave

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Space charge accumulation in XLPE versus temperature and water content

Proceedings of the Nordic Insulation Symposium ◽

10.5324/nordis.v0i23.2447 ◽

2018 ◽

Author(s):

Torbjørn Andersen Ve ◽

Frank Mauseth ◽

Erling Ildstad

Keyword(s):

Electrical Properties ◽

Space Charge ◽

Water Content ◽

Applied Voltage ◽

Insulation Material ◽

Charge Accumulation ◽

Set Up ◽

Xlpe Insulation ◽

Measurement Period ◽

Rate Of Accumulation

<p>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.<br />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.<br />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.</p>

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