Diagnostic Application of Moisture Equilibrium for Power Transformers

Koch, M.; Tenbohlen, Stefan; Stirl, Tobias

doi:10.1109/tpwrd.2010.2048343

Cited by 60 publications

(29 citation statements)

References 3 publications

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“…The oil-paper insulation systems gradually age during long-term operation and the moisture distribution between oil and cellulose insulation paper changes with aging. Maik Koch, Stefan Tenbohlen et al studied the effects of aging on moisture equilibrium curves and found the use of traditional equilibrium curves to estimate moisture in aged oil-paper insulation suffers from severe errors resulting in an overestimation of water concentration [6]. However, the equilibrium curve of only one age degree (130 °C, seven days aging) was drawn [6].…”

Section: Introductionmentioning

confidence: 99%

Thermal aging effects on the moisture equilibrium curves of mineral and mixed oil-paper insulation systems

Liao

Lin

Guo

et al. 2015

IEEE Trans. Dielect. Electr. Insul.

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Moisture equilibrium curves are well accepted methods for moisture estimation of insulation paper in field transformers. The thermal aging effects on moisture partition diagrams of mineral oil-paper and a new aging-resistant mixed oil-paper insulation system were studied. The purpose was to assess the moisture content accurately, particularly in transformers used for long-term operations. Thermal aging experiment was conducted at 130 °C for 80 days, and moisture equilibrium curves at five different aging degrees and three different temperatures were constructed. Results showed that under the same oil moisture content, the moisture content in paper decreased as the aging condition aggravated. The mass fraction of moisture content in oil and paper was calculated at each aging degree. Comparative results revealed that the moisture absorption capacity of insulation paper had an age-related decreasing tendency, whereas the moisture absorption capacity of insulating oil had an age-related increasing tendency. Moisture partition diagrams of mineral and aging-resistant mixed oil-paper samples were compared. Results showed that with the same oil moisture concentration, the moisture of insulation paper impregnated in mixed oil was remarkably lower than that impregnated in mineral oil.

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Section: Introductionmentioning

confidence: 99%

Thermal aging effects on the moisture equilibrium curves of mineral and mixed oil-paper insulation systems

Liao

Lin

Guo

et al. 2015

IEEE Trans. Dielect. Electr. Insul.

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show abstract

“…Thus, by knowing the temperature and water content of the oil, one can estimate the water content in the solid. If the thermal and kinetic equilibrium cannot be guaranteed, these charts can give erroneous estimations additionally to sources of error during oil sampling and measurement in the laboratory [49].…”

Section: Methods Of Moisture Assessmentmentioning

confidence: 99%

Diagnostic Measurements for Power Transformers

et al. 2016

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Abstract:With the increasing age of the primary equipment of the electrical grids there exists also an increasing need to know its internal condition. For this purpose, off-and online diagnostic methods and systems for power transformers have been developed in recent years. Online monitoring is used continuously during operation and offers possibilities to record the relevant stresses which can affect the lifetime. The evaluation of these data offers the possibility of detecting oncoming faults early. In comparison to this, offline methods require disconnecting the transformer from the electrical grid and are used during planned inspections or when the transformer is already failure suspicious. This contribution presents the status and current trends of different diagnostic techniques of power transformers. It provides significant tutorial elements, backed up by case studies, results and some analysis. The broadness and improvements of the presented diagnostic techniques show that the power transformer is not anymore a black box that does not allow a view into its internal condition. Reliable and accurate condition assessment is possible leading to more efficient maintenance strategies.

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“…Thus, one could conclude that NEA retards the hydrolysis reaction in PB giving higher DP values to PB in NEA over time. This is caused by high moisture solubility [16] and hydrolytic degradation of NE itself. As a result, the interaction between water and PB is reduced and, consequently, the hydrolysis reaction in PB in NE is delayed.…”

Section: Decrease In Degree Of Polymerization (Dp) Of Pressboard (Pb)mentioning

confidence: 99%

Performance of Natural Ester as a Transformer Oil in Moisture-Rich Environments

et al. 2016

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Abstract:Interest has risen among utilities in using natural ester (NE) insulating oils in transformers as a substitute for conventional mineral oil. However, present understanding on aging behaviour of NE-paper composite insulation system and knowledge on application of existing condition monitoring tools for NE-based insulation are inadequate. This limits the cost effective and reliable field applications of NE insulating oil. To pave the way the application of NE-based insulation in transformers, a systematic study has been performed to compare the aging behaviour of transformer grade pressboard (PB) impregnated in NE and conventional mineral oil. Applicability of a number of chemical and physical parameters, including acidity value, dielectric dissipation factor (DDF), viscosity, and colour for assessing the quality of NE insulating oil is also discussed in this paper. Comparisons are made based on the limiting values provided in the related IEEE Standard and properties of mineral oil under similar aging conditions.

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Diagnostic Application of Moisture Equilibrium for Power Transformers

Cited by 60 publications

References 3 publications

Thermal aging effects on the moisture equilibrium curves of mineral and mixed oil-paper insulation systems

Thermal aging effects on the moisture equilibrium curves of mineral and mixed oil-paper insulation systems

Diagnostic Measurements for Power Transformers

Performance of Natural Ester as a Transformer Oil in Moisture-Rich Environments

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