Elevated-Temperature Space Charge Characteristics and Trapping Mechanism of Cross-Linked Polyethylene Modified by UV-Initiated Grafting MAH

Abstract

Space charge characteristics of cross-linked polyethylene (XLPE) at elevated temperatures have been evidently improved by the graft modifications with ultraviolet (UV) initiation technique, which can be efficiently utilized in industrial cable manufactures. Maleic anhydride (MAH) of representative cyclic anhydride has been successfully grafted onto polyethylene molecules through UV irradiation process. Thermal stimulation currents and space charge characteristics at the elevated temperatures are coordinately analyzed to elucidate the trapping behavior of blocking charge injection and impeding carrier transport which is caused by grafting MAH. It is also verified from the first-principles calculations that the bound states as charge carrier traps can be introduced by grafting MAH onto polyethylene molecules. Compared with pure XLPE, the remarkably suppressed space charge accumulations at high temperatures have been achieved in XLPE-g-MAH. The polar groups on the grafted MAH can provide deep traps in XLPE-g-MAH, which will increase charge injection barrier by forming a charged layer of Coulomb-potential screening near electrodes and simultaneously reduce the electrical mobility of charge carriers by trap-carrier scattering, resulting in an appreciable suppression of space charge accumulations inside material. The exact consistence of experimental results with the quantum mechanics calculations demonstrates a promising routine for the modification strategy of grafting polar molecules with UV initiation technique in the development of high-voltage DC cable materials.

Water-Tree Characteristics and Its Mechanical Mechanism of Crosslinked Polyethylene Grafted with Polar-Group Molecules

“…The successful modification of chemical grafting on XLPE can be verified by FTIR spectroscopy, which is characterized by stretching vibration peaks at 907 and 1735 cm −1 of vinyl (C=C) and ester (C=O) groups on CAAE and at 912 cm −1 of MAH molecules [ 18 , 19 ], as shown in Figure 1 . In comparison to both the raw material blends before and after vacuum hot-degassing treatment, the CAAE-grafted XLPE (XLPE-g-CAAE) with 1.0 wt% grafting content gives rise to the characteristic peak of C=O groups.…”

Nonlinear Conductivity and Space Charge Characteristics of SiC/Silicone Rubber Nanocomposites

“…Homocharge and heterocharge as two classes of space charges are accumulated by trapping the electrode-injected carriers and the impurity ionized carriers that form the applied electrode and the dielectric material interior, respectively [18][19][20]. Therefore, in the depolarization process, heterocharges decay more quickly than homocharges under a short-circuit as shown in the right panels of Figure 6.…”

Graftable voltage stabilizer for enhancing insulation performance of crosslinked polyethylene

“…3,4 However, the problems of temperature gradient, space charge accumulation and the generation of electrical tree under complex working conditions in XLPE insulation threaten its service life and bring security risks to power systems. [5][6][7] In order to improve the working stability and service life of XLPE insulation cables, the commonly used modification methods are mainly assigned to nanoparticle modification, [8][9][10][11] blending modification, [12][13][14] grafting modification [15][16][17] and voltage stabilizer modification. [18][19][20][21] Since high-voltage power cable insulation materials require high purity, the easy-to-introduce impurities blending modification method is rarely used.…”

“…In order to improve the working stability and service life of XLPE insulation cables, the commonly used modification methods are mainly assigned to nanoparticle modification, 8–11 blending modification, 12–14 grafting modification 15–17 and voltage stabilizer modification 18–21 . Since high‐voltage power cable insulation materials require high purity, the easy‐to‐introduce impurities blending modification method is rarely used.…”

“…Maleic anhydride (MAH) is one of the most popular graft compounds in the study of polymer insulation properties. It has strong polar chemical bonds that can introduce deep charge traps into the polymers, thereby limiting the migration and conduction of carriers in the electric field, increasing the resistivity of the material, and significantly improving the DC insulation performance of XLPE cable insulation materials 17,23,24 . However, it is difficult to improve the AC insulation performance of XLPE cable insulation materials by MAH alone.…”