High dielectric permittivity by ionic space charge polarization in polyethylene oxide

ABSTRACTThin films (0.3μm to 11.2 μm) of Polyethylene Oxide (PEO) with molecular weights from 6 × 103 to 4 × 105 were prepared from aqueous solutions by a spin technique as AI-PEO-AI structures, or as AI-PEO-Si structures. Dielectric measurements (capacitance and loss angle) were carried out in a frequency range 3 mHz ≤ f ≤ 1 MHz in atmospheres of different relative humidity (0% r.h. to 75% r.h.) and at different temperatures (293 K to 323 K). The nominal dielectric permittivity exhibits a remarkable dependence on the sample thickness and the relative humidity. We find a true volume polarization in the high frequency range and a thermally activated relaxation process in the low frequency range, whose time constant is shifted towards high frequencies with increasing r.h.. It is considered that due to the absorbed dipolar water molecules chemical bonds within the sample are broken and quasi-free ions are generated. These ions move through the sample to the electrode interfaces and form an ionic space charge. We assume that at the PEO-Al interface an oxide layer is formed, which is impermeable for these ions. The transit times and the drift velocities of the ions are almost independent of the electric field strength in the low-field limit. Therefore we conclude that the movement of the ions can be described by a multiwell potential model, where the transition probability between neighbored wells is thermally activated.

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High dielectric permittivity of polyethylene oxide in humid atmospheres

Proceedings of Conference on Electrical Insulation and Dielectric Phenomena - CEIDP '96 ◽

10.1109/ceidp.1996.564574 ◽

2002 ◽

Cited By ~ 2

Author(s):

H. Kliem ◽

K. Schroder ◽

W. Bauhofer

Keyword(s):

Dielectric Permittivity ◽

Polyethylene Oxide ◽

High Dielectric Permittivity ◽

High Dielectric

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Effect of Radial Moisture Distribution on Frequency Domain Dielectric Response of Oil-Polymer Insulation Bushing

Polymers ◽

10.3390/polym12061219 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1219 ◽

Cited By ~ 1

Author(s):

Daning Zhang ◽

Guanwei Long ◽

Yang Li ◽

Haibao Mu ◽

Guanjun Zhang

Keyword(s):

Moisture Content ◽

Space Charge ◽

Frequency Domain ◽

Water Distribution ◽

Space Charge Polarization ◽

Moisture Distribution ◽

Mechanism Analysis ◽

Loss Peak ◽

Charge Polarization ◽

Peak Value

In order to realize the diagnosis of water distribution, this paper analyzes the interface polarization and macroscopic space charge polarization mechanism when the water distribution is non-uniform. The experimental results of this paper and bushing show that when the moisture distribution is non-uniform, there is a significant loss peak in the tanδ-f curve. The loss peak shifts to higher frequencies as the non-uniformity coefficient increases. There are common intersection points between multiple tanδ-f curves. Further, this paper realizes the diagnosis of the location of moisture distribution through Frequency Domain Spectroscopy (FDS) testing of different voltages and different wiring methods based on the macroscopic space charge polarization. In the single-cycle FDS test, when the positive electrode is first added to the area with higher moisture content, the amplitude of the tanδ-f curve is smaller. The tanδ-f curves under different wiring methods constitute a “ring-shaped” loss peak. As the voltage increases, the peak value of the loss peak shifts to the lower frequency band. As the temperature increases, the peak value of the loss peak shifts to higher frequencies. Based on the above rules and mechanism analysis, this research provides a new solution for the evaluation of moisture content of oil-immersed polymers equipment.

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