Conductivity and permittivity of midel 7131: effect of temperature, moisture content, hydrostatic pressure and electric field

2016 ◽  
Vol 23 (5) ◽  
pp. 2957-2964 ◽  
Author(s):  
Torstein G. Aakre ◽  
Torbjørn A. Ve ◽  
Øystein L. Hestad
Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2271 ◽  
Author(s):  
Qingguo Chen ◽  
Jinfeng Zhang ◽  
Minghe Chi ◽  
Peng Tan ◽  
Wenxin Sun

The electric field distortion caused by space charge is an important factor affecting the operation reliability of oil–paper insulation in a converter transformer. To study the accumulation and decay characteristics of the space charge within oil-impregnated pressboard under DC and polarity reversal voltage, and consider the possible operating conditions of the converter transformer, the space charge behavior of oil-impregnated pressboard was measured by the pulsed electro-acoustic (PEA) method in the temperature range from −20 °C to 60 °C. The effect of temperature on the accumulation and decay characteristics of space charge is also analyzed. The space charge accumulated within the pressboard at low temperature is mainly homocharge injected by the electrode, while heterocharge formed by ion dissociation counteracts some of the homocharge at high temperature. Thus, the space charge of pressboard first increases, then decreases, with an increase in temperature. However, slow decay of the space charge causes severe distortion of the electric field distribution in the pressboard during voltage polarity reversal.


BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 2656-2667
Author(s):  
Feihu Chang ◽  
Yanhe Liu ◽  
Bin Zhang ◽  
Wansi Fu ◽  
Pengfei Jiang ◽  
...  

In the process of applying the high-frequency heating technology to bamboo heat treatment, controlling the material temperature has a great influence on the quality of bamboo forming. Therefore, research on the heat transfer mechanism of high-frequency heating of arc-shaped bamboo pieces is of great importance. In this paper, the influence of different moisture content, chord length, and plate voltage on the heating rate of arc-shaped bamboo pieces under high-frequency electric field were studied. The moisture content of bamboo had the most remarkable effect on the heating rate. With increased moisture content, the temperature rose faster. The selection of the plate voltage had an obvious influence on the heating. If the voltage was low, the heating rate was too slow, the heating time was long, or the voltage was high, it was easy to cause electric field breakdown and damage the bamboo pieces. As the chord length decreased, the heating rate gradually increased. When the radian of the arc-shaped bamboo pieces could be ignored, the heating rate was the fastest. The results showed that under certain conditions, the arc-shaped bamboo pieces showed a good heat treatment effect in a high-frequency electric field.


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