The dielectric properties of 20% synthetic ester oil mixed with mineral oil were studied for its potential applications as an insulator in transformers. The corona inception voltage of mixed oil under AC and DC voltages was measured by the ultra-high frequency (UHF) technique. A statistical study of the breakdown voltage of mixed oil under AC, DC and standard lightning impulse voltages was carried out to obtain a database which would be useful for designing transformer insulation. Further, the mixture was subjected to continuous breakdown studies under AC voltage with lightning impulse voltages, at regular intervals and characterised through measurement of interfacial tension, flash point, ionic mobility as well as UV–vis spectroscopy and frequency-domain spectroscopy studies to understand the liquid's chemical stability. The results of the study have shown that the mixture was stable even after several breakdowns. The ionic mobility and polarisation current have increased, indicating higher losses in the oil. UHF signal energy analysis and phase-resolved partial discharge analysis have revealed a reduction in discharge activity with mixed oils.

中文翻译：

---

混合矿物油和合成酯油的介电性能

对20％合成酯油与矿物油混合的介电性能进行了研究，探讨了其作为变压器绝缘子的潜在应用。通过超高频（UHF）技术测量了交流和直流电压下混合油的电晕起始电压。对交流，直流和标准雷电冲击电压下混合油的击穿电压进行了统计研究，从而获得了可用于设计变压器绝缘的数据库。此外，在交流电压和雷电冲击电压下，定期对混合物进行连续击穿研究，并通过测量界面张力，闪点，离子迁移率以及紫外可见光谱和频域光谱研究对其进行表征，以了解液体的化学稳定性。研究结果表明，即使经过几次击穿，混合物仍是稳定的。离子迁移率和极化电流增加，表明油中的损失更高。UHF信号能量分析和相分辨的局部放电分析显示混合油的放电活性降低。