Abstract
Employing a novel semiconductor electrode in comparison with the traditional semiconductor electrode made of polyethylene/ethylene-vinyl-acetate copolymer/carbon-black (PE/EVA/CB) composite, characteristic charge carriers are injected into polyethylene terephthalate (PET) as a polymer dielectric paradigm, which will be captured by specific deep traps of electrons and holes. Combined with thermal stimulation current (TSC) experiments and first-principles electronic-state calculations, the injected charges from the novel electrode are characterized, and the corresponding dielectric behavior is elucidated through DC conductance, electrical breakdown and dielectric spectrum tests. TSC experiments with novel and traditional semiconductor electrodes can distinguish the trapping characteristics between hole and electron traps in polymer dielectrics. The observable discrepancy in space charge-limited conductance and the stable dielectric breakdown strength demonstrate that the electron injection into PET film specimen is restricted by using the novel semiconductor electrode. Attributed to the favorable suppression on the inevitable electron injections from metal electrodes, adopting novel i-electrode can avoid the evident abatement of dipole orientation polarization caused by space charge clamp, but will engender the accessional high-frequency dielectric loss from dielectric relaxations of interface charges at i-electrodes.
Highlights
In electrical power systems of high voltage direct current (HVDC) transmission, polymer materials used for the insulation layer in power transmission cables are susceptible to suffering space charge accumulations that could expedite electrical aging and breakdownfailure process, which leads to an evident abatement in working life and operation stability of HVDC cable [1,2,3]
In order to investigate charge injection of adopting different3 of 11 in wh polyethylene terephthalate (PET)/electrode testingthesystem for 30characteristics min at ambient temperature, semiconductor electrodes, thermal stimulation current (TSC) of PET‐electrode system are tested to calculate energy injected from electrodes into PET material and being captured by cha level distributions of charge traps that have captured the charge carriers injected from charge injection, the applied voltage is short‐circuit removedinout, and semiconductor electrodes
Charge carriers injected into polymer dielectrics are more liable to be captured by deep traps than shallow traps, resulting in fewer carriers being trapped into the intrinsic shallow traps of structural defects in PET
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Traditional semi-conductive shielding layer used in transmission cable is composed of polyethylene/ethylene-vinyl-acetate copolymer (PE/EVA) and carbon-black (CB), on which multiple schemes such as controlling copolymer composition, introducing modifiers, adding fillers, and matching interface have been implemented to ameliorate space charge distributions in insulation layer [14,15,16,17]. Numerical simulation technology can be exploited to reveal the experimentally unattainable attributes such as local electric field distribution, ion thermodynamics, and high-current pulsed surface discharge, which is of great significance to study the charge transport mechanism of dielectrics/semiconductor interfaces [22,23,24]. A new type of semiconductor electrode (ionic-electrode, abbreviated as i-electrode in this paper) and the traditional semiconductor electrode made of polyethylene/ethylene-vinyl-acetate copolymer and carbon-black (PE/EVA/CB) composite (electronic-electrode, abbreviated as e-electrode in this paper) are employed to comparatively investigate the charge injection characteristics and the resulted dielectric performances. After applying PET film samples with various levels of voltages by using different semiconductor electrodes, the electrical breakdown experiment and dielectric spectrum test are implemented to explore the acquired insulation performance by semiconductor electrodes and their effects on the dielectric behavior of PET
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