Article

Investigations of Temperature Effects on the Dielectric Response Measurements of Transformer Oil-Paper Insulation System

Queensland Univ., Brisbane
IEEE Transactions on Power Delivery (Impact Factor: 1.52). 02/2008; DOI: 10.1109/TPWRD.2007.911123
Source: IEEE Xplore

ABSTRACT Dielectric testing techniques, in both time and frequency domains, are currently widely used by power utilities for assessment of the condition of transformer oil-paper insulation systems. However, it has been reported that results of these tests are highly influenced by the operating temperature during measurements. The distribution, migration and equilibrium of moisture between oil and paper in a complicated insulation system is highly temperature dependent. It requires adequate experience and proper understanding to interpret the dielectric response results in the presence of temperature variations and thermal instability. Proper analysis of the dielectric test result is only possible with an understanding of the physical behavior of the insulation system in response to temperature. A circuit model, which describes the dielectric behavior of the transformers main insulation system, has been investigated in this paper. The values of the parameters of the model have been identified from the dielectric tests. A correlation has been observed between the operating temperature and the equivalent model parameters that can be used as additional information for better interpretation of the dielectric test results. This paper thus reports a detailed study on the effects of temperature on dielectric measurements of a transformer under controlled laboratory conditions. Some results of practical on-site testing are also presented to demonstrate the possibility of errors that may be introduced in dielectric test results analysis unless temperature effects are taken into consideration.

4 Bookmarks
 · 
248 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Dielectric diagnosis with polarization and depolarization currents (PDC) which employs the dielectric response of system in time domain is applied to investigate differences between PDC patterns produced by two types of transformer insulating fluids, mineral and bio-degradable oil. The mineral oil used is Shell Diala BX, and the biodegradable one is Envirotemp FR3. The latter is ester-based, and a relatively new transformer insulating fluid introduced as an environmentally-friendly alternative to conventional mineral oil. The DC conductivity of the two oil types is obtained under the effects of various temperature and moisture levels. The experiment is conducted for two levels of moisture when temperature factor is changed from ambient to 90 °C. The oil water content measurement is conducted using Karl-Fischer-Titration. Also, an attempt was made to investigate the effects that different testing voltages and time durations have on the polarization and depolarization spectrum. A range of DC voltages up to 1000V, and time durations from 1000 to 10000 seconds have been applied. Finally, all the PDC patterns obtained under the effect of mentioned factors are evaluated.
    IPEC, 2012 Conference on Power & EnergyIPEC, 2012 Conference on Power & Energy; 01/2012
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Frequency Domain Spectroscopy (FDS) is an effective tool allowing assessing the condition of oil-paper insulation system in power equipment. However, results from these measurements are known to be greatly influenced by various parameters, including insulation aging, moisture content, and insulation geometry/volume, together with environmental condition such as temperature. In this contribution, a series of experiments have been performed under controlled laboratory conditions. The dielectric response of the oil impregnated paper, along with the degree of polymerization and moisture content, were monitored. Since dielectric parameters are geometry dependent, poles (independent of the geometry) which depends on resistivity and permittivity, were considered to assess the condition of the insulation. From the investigations performed on new and aged samples, it is shown that poles (P) can be regarded as insulation aging indicator. It is also shown that a per unit value based on the Dielectric Dissipation Factor (DDF), measured in the frequency range from 1 to 1000 Hz can be correlated to moisture content in the insulation paper.
    Energies 01/2013; 6:2204-2220. · 1.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Conference code: 98676, Export Date: 10 September 2013, Source: Scopus, Art. No.: 6564511, doi: 10.1109/PEOCO.2013.6564511, Language of Original Document: English, Correspondence Address: Institute of High Voltage and High Current (IVAT), Universiti Teknologi Malaysia (UTM), 81300 Skudai, Johor, Malaysia, References: Gafvert, U., Dielectric spectroscopy in time and frequency domain applied to diagnostics of power transformers (2000) Properties and Applications of Dielectric Materials 2000. Proceedings of the 6th International Conference on, 2, pp. 825-830;, Sponsors: IEEE Malaysia, Power and Energy Chapter (PES)
    Proceedings of the 2013 IEEE 7th International Power Engineering and Optimization Conference, PEOCO 2013, Langkawi; 01/2013

Full-text (2 Sources)

View
12 Downloads
Available from
Oct 3, 2014