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Quantitative analysis of ageing condition of oil-paper insulation by frequency domain spectroscopy

Quantitative analysis of ageing condition of oil-paper insulation by frequency domain spectroscopy
Quantitative analysis of ageing condition of oil-paper insulation by frequency domain spectroscopy
Frequency domain spectroscopy (FDS) has been used to assess the ageing condition of oil-paper insulation used in transformers. To further understand the ageing process, the reduction in degree of polymerization (DP) of cellulosic paper in itself on the dielectric response was investigated first. It has been found that the reduction in DP itself can alter the dielectric characteristics. The oil-paper insulation was thermally accelerated aged at 110 °C for up to 154 days according to the procedure described in IEEE Guide. Then dielectric characteristics of the thermally aged samples were obtained at different measurement temperatures. The results reveal that the relative permittivity (?') plots of oil impregnated pressboards increase with the reduction in cellulose polymer chain length. ?' and tan? values of oil impregnated pressboards shifts upwards in the lower frequency range (10-3 Hz -10-1 Hz) with different ageing condition, indicating the possibility of utilizing the characteristics of ?' and tan? values at lower frequencies (10-3 Hz-10-1 Hz) to quantitatively characterize ageing condition of oil impregnated pressboard. The parameters including DP, ?' and tan? values at the three characteristic frequencies (10-3 Hz, 10-2 Hz, 10-1 Hz) have been analyzed as a function of the ageing time, showing an exponential relationship based on the best fit. In addition, the ?' and tan? curves of aged oil impregnated pressboard have been observed to be shifted upwards to higher values at lower frequencies when the measurement temperature is increased. A shifting factor ?T which describes the relationship between frequency and temperature has been defined. It allows one to shift the master curve of impregnated pressboard with DP obtained at reference temperature to other testing temperatures.

frequency domain spectroscopy, oil-paper insulation, ageing condition, permittivity, dielectric loss, quantitative analysis
1070-9878
821-830
Liao, Ruijin
e10ba49b-110d-4e1d-a102-b1a4e4a0b7e2
Hao, Jian
01bbfea6-2a3e-40b3-bb0c-1c16d6dcd66d
Chen, George
3de45a9c-6c9a-4bcb-90c3-d7e26be21819
Yang, Lijun
da9c0071-a555-45cb-b5d6-274fbf2dcc0a
Liao, Ruijin
e10ba49b-110d-4e1d-a102-b1a4e4a0b7e2
Hao, Jian
01bbfea6-2a3e-40b3-bb0c-1c16d6dcd66d
Chen, George
3de45a9c-6c9a-4bcb-90c3-d7e26be21819
Yang, Lijun
da9c0071-a555-45cb-b5d6-274fbf2dcc0a

Liao, Ruijin, Hao, Jian, Chen, George and Yang, Lijun (2012) Quantitative analysis of ageing condition of oil-paper insulation by frequency domain spectroscopy. IEEE Transactions on Dielectrics & Electrical Insulation, 19 (3), 821-830. (doi:10.1109/TDEI.2012.6215085).

Record type: Article

Abstract

Frequency domain spectroscopy (FDS) has been used to assess the ageing condition of oil-paper insulation used in transformers. To further understand the ageing process, the reduction in degree of polymerization (DP) of cellulosic paper in itself on the dielectric response was investigated first. It has been found that the reduction in DP itself can alter the dielectric characteristics. The oil-paper insulation was thermally accelerated aged at 110 °C for up to 154 days according to the procedure described in IEEE Guide. Then dielectric characteristics of the thermally aged samples were obtained at different measurement temperatures. The results reveal that the relative permittivity (?') plots of oil impregnated pressboards increase with the reduction in cellulose polymer chain length. ?' and tan? values of oil impregnated pressboards shifts upwards in the lower frequency range (10-3 Hz -10-1 Hz) with different ageing condition, indicating the possibility of utilizing the characteristics of ?' and tan? values at lower frequencies (10-3 Hz-10-1 Hz) to quantitatively characterize ageing condition of oil impregnated pressboard. The parameters including DP, ?' and tan? values at the three characteristic frequencies (10-3 Hz, 10-2 Hz, 10-1 Hz) have been analyzed as a function of the ageing time, showing an exponential relationship based on the best fit. In addition, the ?' and tan? curves of aged oil impregnated pressboard have been observed to be shifted upwards to higher values at lower frequencies when the measurement temperature is increased. A shifting factor ?T which describes the relationship between frequency and temperature has been defined. It allows one to shift the master curve of impregnated pressboard with DP obtained at reference temperature to other testing temperatures.

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More information

Published date: June 2012
Keywords: frequency domain spectroscopy, oil-paper insulation, ageing condition, permittivity, dielectric loss, quantitative analysis
Organisations: EEE

Identifiers

Local EPrints ID: 340312
URI: http://eprints.soton.ac.uk/id/eprint/340312
ISSN: 1070-9878
PURE UUID: a90d6bd5-b933-47d0-ae4e-0aabb7b58cc7

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Date deposited: 18 Jun 2012 11:22
Last modified: 02 Dec 2019 20:57

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