Assessment of transformer mineral oil condition based on dc and ac conductivity

Badicu, L. V.; Gorgan, Bogdan; Dumitran, Laurentiu Marius; Notingher, P.

doi:10.1109/tdei.2012.6311499

Cited by 28 publications

(9 citation statements)

References 15 publications

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“…In the dielectric theory about complex permittivity [17][18][19], the real part of complex permittivity indicates the polarisation characteristics of dielectric, and the imaginary part indicates the loss of dielectric during the testing process. The essential process of frequency-domain dielectric response is the conductivity of the dielectric under AC electrical field [20]. The complex permittivity of dielectric has the following relations with its conductivity [21]:…”

Section: Elimination Of Temperature Effectsmentioning

confidence: 99%

Moisture estimation for oil‐immersed bushing based on FDS method: field application

Wang

Zhou

Liao

et al. 2018

IET Generation, Transmission & Distribution

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Section: Elimination Of Temperature Effectsmentioning

confidence: 99%

Moisture estimation for oil‐immersed bushing based on FDS method: field application

Wang

Zhou

Liao

et al. 2018

IET Generation, Transmission & Distribution

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“…Because insulation oil is a kind of weak electrolyte, and the dissociation time of ionic pair is far less than the time that ion moves from one electrode to the other [25], thus the value of c can be assumed to be constant. When the insulation oil reaches thermal equilibrium, we have

\frac{normald n_{+}}{normald t} = \frac{d n_{-}}{d t} = 0

Namely

n_{+} = n_{-} = n_{0}

k_{D} false(0 false) c = k_{R} n_{+} n_{-} = k_{R} n_{0}^{2}

The values of n + and n − can be calculated from [21]

n_{0} = \frac{σ_{0}}{q false(μ_{+} + μ_{-} false)}

where μ + and μ − are the mobilities of the positive and negative ions, respectively, and σ 0 is the initial bulk conductivity of the insulation oil. k R can be obtained as [26]

k_{R} = \frac{false(μ_{+} + μ_{-} false) q}{ε}

…”

Section: Model Of Low‐frequency Dielectric Responsementioning

confidence: 99%

“…In engineering, the oil gap is simply regarded as a fixed conductance to analyse the dielectric spectrum of oil‐paper insulation [18]. However, it can be known from recent studies that the apparent conductivity of oil gap is not unchanged in the test process, which can be result in the errors of diagnose result [21]. Therefore, a more practical and accurate model, which can reflect the response of oil gap, is needed to analyse the dielectric spectrum of oil‐paper insulation system.…”

Section: Introductionmentioning

confidence: 99%

Modelling the low‐frequency dielectric response test of insulation oil

Wang

Zhou

Chen

et al. 2017

IET Electric Power Applications

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The frequency domain dielectric response method has been one of the most effective approaches for condition assessment of an electrical insulation system. The low-frequency part is more effective for diagnosing the moisture content and aging status of oil-paper insulation. To facilitate the study of the low-frequency dielectric spectrum of oil-paper insulation, a model applicable to the low-frequency dielectric response of insulation oil is proposed in this study, which is based on the ionic motion of insulation oil. The creation of charge carriers under field test conditions mainly derives from the dissociation of ionic pairs. During testing, ionic motion of insulation oil is jointly affected by thermal diffusion and the electric field; moreover, dissociation and recombination of negative and positive ions also occur. Therefore, the above factors were all considered in the modelling process. The applicability of the model is verified against measured results. For further interpreting the proposed model, the characteristics of the ionic concentration distribution, the relation between ionic distribution and dielectric properties, and the application of the proposed model are analysed.

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“…According to the theory of repolarisation rate and dielectric relaxation, the response of the dielectric in the time‐harmonic field can be described by the Cole–Cole model with two relaxation processes in a wide frequency range [12–14]. Direct‐current (DC) conductivity usually affects the complex permittivity at the frequency below 1 Hz [13]. Therefore, the basic model of dielectric response of this paper can be described as follows: