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Proceedings ArticleDOI

On-line assessment of moisture in a power transformer

TL;DR: An online method for the assessment of moisture in a power transformer is presented and it is shown that the method is clearly able to distinguish between levels of humidity in the range of interest.
Abstract: An online method for the assessment of moisture in a power transformer is presented in this paper. It is experimentally tested on simple insulating materials as well as on a sample bushing insulation. It is finally tested during the drying of a 110 kV transformer. The results are presented and show that the method is clearly able to distinguish between levels of moisture in the range of interest.
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Journal ArticleDOI
TL;DR: A description of commonly used chemical diagnostics techniques along with their interpretation schemes for transformer insulation condition assessment is presented.
Abstract: Cellulosic paper and oil insulation in a transformer degrade at higher operating temperatures. Degradation is accelerated in the presence of oxygen and moisture. Power transformers being expensive items need to be carefully monitored throughout their operation. Well established time-based maintenance and conservative replacement planning is not feasible in a current market driven electricity industry. Condition based maintenance and online monitoring are now gaining importance. Currently there are varieties of chemical and electrical diagnostic techniques available for insulation condition monitoring of power transformers. This paper presents a description of commonly used chemical diagnostics techniques along with their interpretation schemes. A number of new chemical techniques are also described in this paper. A number of electrical diagnostic techniques have gained exceptional importance to the utility professionals. Among these techniques polarisation/depolarisation current measurement, return voltage measurement and frequency domain dielectric spectroscopy at low frequencies are the most widely used. This paper describes analyses and interpretation of these techniques for transformer insulation condition assessment.

680 citations


"On-line assessment of moisture in a..." refers methods in this paper

  • ...There are a number of offline methods that can accomplish this task to some extent [1,2,3]....

    [...]

Journal ArticleDOI
TL;DR: In this article, the theoretical background of dielectric spectroscopy in the time and frequency domains is introduced and an overview about the specific measuring methods based on this background is provided, and specific methods treated are used for diagnosing electric insulation materials used in power engineering.
Abstract: Most dangerous breakdowns are caused by the aging effects of HV insulation systems used within HV components, and there is still a lack of appropriate tools to diagnose such systems non-destructively and reliably in the field. This review introduces the theoretical background of dielectric spectroscopy in the time and frequency domains and provides an overview about the specific measuring methods based on this background. The specific methods treated are used for diagnosing electric insulation materials used in power engineering. It indicates that some of these methods may not be sufficient to gain full information about the actual conditions of a test object and that either measurements of polarization and depolarization currents (PDC in the time domain or measurements of C-tan/spl delta/ values (or complex permittivity) in the frequency domain (FDS) should be preferred to obtain a "dielectric response function" which offers much more information to judge the actual state of an insulation material or system.

469 citations


"On-line assessment of moisture in a..." refers methods in this paper

  • ...There are a number of offline methods that can accomplish this task to some extent [1,2,3]....

    [...]

Journal ArticleDOI
TL;DR: In this article, the authors proposed an off-line, on-site insulation condition assessment of HV electric power equipment and its predictive maintenance using dielectric spectroscopy in the time or frequency domain.
Abstract: Dielectric spectroscopy in the time or frequency domain offers new opportunities for an off-line, on-site insulation condition assessment of HV electric power equipment and its predictive maintenance.

361 citations

Book
01 Dec 1987
TL;DR: In this paper, the physical background of Transformer operation is discussed, including the core, the windings, and the insulation of the Transformer's structural parts, as well as the temperature rise and cooling of Transformers.
Abstract: 1. The Physical Background of Transformer Operation. 2. The Core. 3. The Windings. 4. Stray-Field Losses in Structural Parts of Transformers. 5. Transformer Insulation. 6. Temperature Rise and Cooling of Transformers. 7. Constructional Parts of the Transformer. Subject Index.

184 citations


"On-line assessment of moisture in a..." refers background or methods in this paper

  • ...This is similar to the process for a thermal image [5]....

    [...]

  • ...Conceptually it is similar to a thermal image that is used in transformers [5], with the added qualification that the surrounding insulation is specially designed and monitored....

    [...]

Journal ArticleDOI
TL;DR: In this article, the degradation of electrical kraft paper under carefully controlled laboratory experiments is examined in order to find correlations between the change in dielectric and mechanical properties and the increase in concentration of furan compounds in the oil.
Abstract: The degradation of electrical kraft paper under carefully controlled laboratory experiments is being examined in order to find correlations between the change in dielectric and mechanical properties and the increase in concentration of furan compounds in the oil. These correlations could be valuable for assessing the extent of degradation of paper insulation in operating HV equipment. Preliminary investigation has shown that the concentration of furan compounds in mineral oil can be determined relatively easily using high-performance liquid chromatography (HPLC). While some of these compounds are themselves unstable, three have been found which are worth monitoring to correlate with the tensile and dielectric properties of the paper. Useful trends have been obtained, and further investigation is taking place to obtain clear cut correlation of practical value for monitoring the condition of actual transformers. >

126 citations


"On-line assessment of moisture in a..." refers methods in this paper

  • ...There are a number of offline methods that can accomplish this task to some extent [1,2,3]....

    [...]