This paper reports the key findings from an experimental study carried out on thermally aged natural ester fluid impregnated pressboard (EOIP) material. The results show that the surface discharge inception voltage (SDIV) with thermally aged EOIP material is higher under negative DC voltage compared with positive DC and AC voltage. The SDIV increases with AC voltage frequency and a minimal reduction in voltage was observed under harmonic AC voltages with different total harmonic distortion (THD). The rate of change in voltage due to ripple content in DC voltage affects the SDIV of EOIP material, initiating discharges at lower voltages. The UHF signals radiated during the surface discharge process have a bandwidth in the range 0.9 to 2 GHz. Surface potential variation studies indicated the formation of high trap sites and trap density due to thermal aging. A reduction in the oxidation onset temperature and the activation energy of thermal decomposition were observed with thermally aged EOIP material. A pyrolysis study showed high composition of levoglucosan and acidic residue with the thermally aged specimen, which reduces its degree of polymerization. Impedance spectroscopic analysis indicates a non-Debye type of relaxation with thermally aged EOIP material. The mobility and charge transfer characteristics were also inferred from the modulus spectroscopy which showed less change for thermally aged pressboard material.

中文翻译：

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热老化天然酯流体浸渍纸板材料的性能研究

本文报告了对热老化天然酯流体浸渍纸板 (EOIP) 材料进行的实验研究的主要发现。结果表明，与正直流和交流电压相比，热老化 EOIP 材料的表面放电起始电压 (SDIV) 在负直流电压下更高。SDIV 随着交流电压频率的增加而增加，并且在具有不同总谐波失真 (THD) 的谐波交流电压下观察到电压的最小降低。由于直流电压中的纹波含量而导致的电压变化率影响 EOIP 材料的 SDIV，从而在较低电压下启动放电。在表面放电过程中辐射的 UHF 信号的带宽在 0.9 到 2 GHz 范围内。表面电位变化研究表明由于热老化形成了高陷阱位点和陷阱密度。使用热老化的 EOIP 材料观察到氧化起始温度和热分解活化能的降低。热解研究表明，热老化样品中左旋葡聚糖和酸性残留物的高组成，这降低了其聚合度。阻抗光谱分析表明热老化 EOIP 材料出现非德拜型弛豫。迁移率和电荷转移特性也从模量光谱中推断出来，表明热老化纸板材料的变化较小。热解研究表明，热老化样品中左旋葡聚糖和酸性残留物的高组成，这降低了其聚合度。阻抗光谱分析表明热老化 EOIP 材料出现非德拜型弛豫。迁移率和电荷转移特性也从模量光谱中推断出来，表明热老化纸板材料的变化较小。热解研究表明，热老化样品中左旋葡聚糖和酸性残留物的高组成，这降低了其聚合度。阻抗光谱分析表明热老化 EOIP 材料出现非德拜型弛豫。迁移率和电荷转移特性也从模量光谱中推断出来，表明热老化纸板材料的变化较小。