Effect of crosslinking on space charge formation in crosslinked polyethylene

Hirai, Naoshi; Maeno, Y.; Tanaka, Toshikatsu; Ohki, Yoshimichi; Okashita, M.; Maéno, Takashi

doi:10.1109/icpadm.2003.1218571

Cited by 13 publications

(5 citation statements)

References 15 publications

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“…The reason for using LDPE over XLPE is to eliminate any possibility of having more than one byproduct in the system. Even though previous studies by N. Hirai [6] show that space charge characteristics in LDPE and degassed XLPE are similar, it has been proven that under stress, the amount of space charge accumulation differs [7] . In addition, the possibility of having byproduct-free XLPE via degassing cannot be guaranteed [8], thus, LDPE is chosen over XLPE.…”

Section: Sample Preparationmentioning

confidence: 85%

Analysis of space charge formation in LDPE in the presence of crosslinking byproducts

Hussin

Chen

2012

IEEE Trans. Dielect. Electr. Insul.

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Cross-linking byproducts are suspected to be the main contributing factor in space charge formation observed in XLPE. To investigate the mechanism behind this phenomenon, low density polyethylene was soaked into three main crosslinking byproducts, acetophenone, -methylstyrene and cumyl alcohol, and space charge measurements were performed using the Pulse Electroacoustic technique (PEA). It has been found that soaking LDPE in cumyl alcohol introduces more charges into the system, with homocharges and heterocharges accumulating within the sample compared to the additive free sample. In contrast, -methylstyrene and acetophenone reduce the amount of accumulated charges. In terms of charge decay, all three byproducts enhance the decay process in the insulator. Further investigations were conducted in conditions where two byproducts are present in a sample. The results shows that acetophenone is a dominant byproduct in determining the charge density patter built up during the charging process, whilst the rate of charge decay is observed to be high in the presence of -methylstyrene in the sample.

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Section: Sample Preparationmentioning

confidence: 85%

Analysis of space charge formation in LDPE in the presence of crosslinking byproducts

Hussin

Chen

2012

IEEE Trans. Dielect. Electr. Insul.

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“…This is represented by the dotted line shown in Figure 4 The by-products generated from crosslinking include acetophenone, alpha methyl styrene, cumyl alcohol and water. It has been reported that acetophenone generates ionic charges in XLPE when coexist with water [24].…”

Section: As-received Samples (Samples a To D)mentioning

confidence: 99%

Temperature effect on space charge dynamics in XLPE insulation

Chong

Chen

2007

IEEE Trans. Dielect. Electr. Insul.

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This paper reports on space charge evolution in crosslinked polyethylene (XLPE) planar samples approximately 1.20 mm thick subjected to electric stress level of 30 kV dc /mm at four temperatures 25, 50, 70 and 90 o C for 24 h. Space charge profiles in both asreceived and degassed samples were measured using the laser induced pressure pulse (LIPP) technique. The dc threshold stresses at which space charge initiates are greatly affected by testing temperatures. The results suggest that testing temperature has numerous effects on space charge dynamics such as enhancement of ionic dissociation of polar crosslinked by-products, charge injection, charge mobility and electrical conductivity. Space charge distributions of very different nature were seen at lower temperatures when comparing the results of as-received samples with degassed samples. However at higher temperature, the space charge distribution took the same form, although of lower concentration in degassed samples. Space charge distributions are dominated by positive charge when tested at high temperatures regardless of sample treatment and positive charge propagation enhances as testing temperature increases. This can be a major cause of concern as positive charge propagation has been reported to be related to insulation breakdown.

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“…This could be due to the byproducts generated from the crosslinking reaction, such as acetophenone, -methylstyrene, cumyl alcohol and water [7]. It has been previously reported the acetophenone leads to the formation of ionic charges in XLPE when it coexists with water and, therefore, leads to increased electrical conductivity [8]. This suggests that undegassed samples (with more byproducts) would contain more free charge carriers in comparison with degassed XLPE.…”

Section: Sample Characterizationmentioning

confidence: 92%

The impacts of degassing on space charge characteristics and DC conductivity in semicon-bonded XLPE for HVDC cable applications

Hao

Fazal²,

Vaughan

et al. 2016

2016 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP)

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-High voltage direct current (HVDC) cables are one of the key components for the HVDC power transmission system. HVDC cables for higher voltage level, larger power capacity and higher reliability are still desired for the power industry as part of a global power strategy. One of the major concerns related to HVDC applications is the presence of space charge within the dielectrics, which distorts the electric field distribution and contributes to accelerated ageing and consequent failure of the cable insulation. The byproducts generated from the crosslinking process during the manufacture of XLPE insulation for HVDC cable are one of the major sources of hetero-charge formation in dielectrics. Therefore, degassing is widely applied in cable manufacture for the removal of such crosslinking byproducts. In this paper, composite XLPE samples were produced that include two layers of semiconductive polymer (semicon), which are thermally bonded on the top and bottom of the XLPE insulation, to mimic a real cable manufacturing process. The samples were degassed under vacuum and elevated temperature for 1, 3 and 6 days and their space charge characteristics and conductivities were then measured at an applied field of 40 kV/mm. The influence of the degassing period and the semicon material formulation on space charge formation and distribution in the system are discussed and the findings are compared with undegassed samples.

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Effect of crosslinking on space charge formation in crosslinked polyethylene

Cited by 13 publications

References 15 publications

Analysis of space charge formation in LDPE in the presence of crosslinking byproducts

Analysis of space charge formation in LDPE in the presence of crosslinking byproducts

Temperature effect on space charge dynamics in XLPE insulation

The impacts of degassing on space charge characteristics and DC conductivity in semicon-bonded XLPE for HVDC cable applications

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