This paper discusses approaches to measure moisture in power transformers by analyzing the dielectric response of the main insulation. Dielectric diagnostic methods deduce moisture in the solid insulation from dielect...This paper discusses approaches to measure moisture in power transformers by analyzing the dielectric response of the main insulation. Dielectric diagnostic methods deduce moisture in the solid insulation from dielectric properties like polarisation depolarisation currents and dissipation factor vs. frequency. A new instrument "Dirana" combines time domain (PDC) and frequency domain (FDS) measurements and thus substantially shortens the measurement duration. New software was developed which bases on a new data pool,measured at new and aged pressboard samples with various moisture contents and oil impregnation. Its analysis algorithm compares measurements from a transformer to modelled dielectric responses,obtained from the so-called XY-model. To avoid overestimation of moisture for aged transformers,the analysis algorithm compensates for the influence of conductive aging by-products. Moisture especially increases the losses in the low frequency range of the dielectric response of pressboard. Thus,data on the left-hand side of the area dominated by interfacial polarization (insulation geometry) are required for reliable moisture determination. Case studies illustrate the application of moisture determination by dielectric response methods.展开更多
为了研究绝缘油老化对变压器油纸绝缘时域介电特性测量结果的影响,以更准确地分析和评估油纸绝缘老化状态,对油浸纸试品进行加速热老化,获取3组不同老化程度的变压器油试样并分析其理化参数。对新绝缘纸试品进行真空干燥,然后使用3组油...为了研究绝缘油老化对变压器油纸绝缘时域介电特性测量结果的影响,以更准确地分析和评估油纸绝缘老化状态,对油浸纸试品进行加速热老化,获取3组不同老化程度的变压器油试样并分析其理化参数。对新绝缘纸试品进行真空干燥,然后使用3组油样分别对干燥的纸样进行充分浸渍获得3组油老化状态不同的油浸纸试品。对每组油浸纸试品进行极化去极化电流(polarization and depolarization currents,PDC)测量,分析油老化引起的油纸绝缘时域介电特性变化。结果表明,变压器油老化后,油中微水含量、酸值、介质损耗因数显著增大,pH值、电阻率减小;油浸纸试品的极化、去极化电流增大,电导电流增大且需要较长时间达到稳定值;试品绝缘电阻R60和吸收比Ka减小。展开更多
文摘This paper discusses approaches to measure moisture in power transformers by analyzing the dielectric response of the main insulation. Dielectric diagnostic methods deduce moisture in the solid insulation from dielectric properties like polarisation depolarisation currents and dissipation factor vs. frequency. A new instrument "Dirana" combines time domain (PDC) and frequency domain (FDS) measurements and thus substantially shortens the measurement duration. New software was developed which bases on a new data pool,measured at new and aged pressboard samples with various moisture contents and oil impregnation. Its analysis algorithm compares measurements from a transformer to modelled dielectric responses,obtained from the so-called XY-model. To avoid overestimation of moisture for aged transformers,the analysis algorithm compensates for the influence of conductive aging by-products. Moisture especially increases the losses in the low frequency range of the dielectric response of pressboard. Thus,data on the left-hand side of the area dominated by interfacial polarization (insulation geometry) are required for reliable moisture determination. Case studies illustrate the application of moisture determination by dielectric response methods.
文摘为了研究绝缘油老化对变压器油纸绝缘时域介电特性测量结果的影响,以更准确地分析和评估油纸绝缘老化状态,对油浸纸试品进行加速热老化,获取3组不同老化程度的变压器油试样并分析其理化参数。对新绝缘纸试品进行真空干燥,然后使用3组油样分别对干燥的纸样进行充分浸渍获得3组油老化状态不同的油浸纸试品。对每组油浸纸试品进行极化去极化电流(polarization and depolarization currents,PDC)测量,分析油老化引起的油纸绝缘时域介电特性变化。结果表明,变压器油老化后,油中微水含量、酸值、介质损耗因数显著增大,pH值、电阻率减小;油浸纸试品的极化、去极化电流增大,电导电流增大且需要较长时间达到稳定值;试品绝缘电阻R60和吸收比Ka减小。
