Fundamental property of electric field in rapeseed ester oil based on Kerr electro-optic measurement

Nakamura, Kohji; Katō, K.; Koide, Hidenobu; Hatta, Y.; Ōkubo, H.

doi:10.1109/tdei.2006.1657974

Cited by 23 publications

(9 citation statements)

References 10 publications

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“…We find that Equation (2) is not only fit for the change of DP for mineral oil immersed paper insulation, but also fit for the change of DP for natural ester immersed paper insulation. Figures 2 and 3 show the DP value curve drawn as Equation (2) during aging process at 90, 110, and 1308C. Obviously, both Kraft paper and thermally upgraded paper in natural ester showed noticeably less degradation than paper in mineral oil.…”

Section: Degree Of Polymerizationmentioning

confidence: 99%

A comparative study of thermal aging of transformer insulation paper impregnated in natural ester and in mineral oil

Liao

Liang

Sun

et al. 2009

Int Trans Elec Energy Syst

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SUMMARYAging of two kinds of transformer insulation paper in natural ester is compared to that in conventional transformer oil (mineral oil). Sealed aging vessels containing copper, insulation paper (Kraft paper and thermally upgraded paper), and dielectric fluid (mineral oil and natural ester) were aged at 90, 110, and 1308C for 399, 371, and 329 days. Under the same aging condition, both the degree of polymerization (DP) and the leveling-off degree of polymerization (LODP) for natural ester aged paper were higher than the ones for mineral oil aged paper, and the micro surface of natural ester aged paper was destroyed less seriously than that of the mineral oil aged paper. The aging time to reach LODP for natural ester aged paper was only 1/4 to 2/3 of that for mineral oil aged paper. When water content in natural ester for natural ester aged Kraft paper samples reached the maximum, acids concentration in natural ester increased abruptly. Water content in natural ester decreased in the whole aging process for natural ester aged thermally upgraded paper samples. Six physical and chemical mechanisms for the slower aging rate of natural ester aged paper are proposed. Evidence for transesterification between natural ester and paper was presented with infrared spectra instrument. Although the acids in natural ester were far more than in mineral oil, the natural ester can significantly slow the thermal aging of the paper. Three mechanisms of this abnormal phenomenon were presented.

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Section: Degree Of Polymerizationmentioning

confidence: 99%

A comparative study of thermal aging of transformer insulation paper impregnated in natural ester and in mineral oil

Liao

Liang

Sun

et al. 2009

Int Trans Elec Energy Syst

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“…11,12 The Kerr electro-optic field mapping technique with AC modulation can be used to measure electric field and space charge distributions in transformer oil under high DC voltages, but this method cannot be applied to electric field and space charge measurements under impulse voltages. [13][14][15] In power system, switching impulse overvoltage, which is caused by switching operation on power apparatus, could lead to serious damage to the transformer oil-paper insulation system of transformers, and thus endanger the security of the power system. The switching breakdown voltage of transformer oil is one of the most important dielectric properties of transformer oil.…”

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confidence: 99%

Space charge inhibition effect of nano-Fe3O4 on improvement of impulse breakdown voltage of transformer oil based on improved Kerr optic measurements

Yang

Sima

et al. 2015

AIP Advances

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Transformer oil-based nanofluids (NFs) with 0.03 g/L Fe3O4 nanoparticle content exhibit 11.2% higher positive impulse breakdown voltage levels than pure transformer oils. To study the effects of the Fe3O4 nanoparticles on the space charge in transformer oil and to explain why the nano-modified transformer oil exhibits improved impulse breakdown voltage characteristics, the traditional Kerr electro-optic field mapping technique is improved by increasing the length of the parallel-plate electrodes and by using a photodetector array as a high light sensitivity device. The space charge distributions of pure transformer oil and of NFs containing Fe3O4 nanoparticles can be measured using the improved Kerr electro-optic field mapping technique. Test results indicate a significant reduction in space charge density in the transformer oil-based NFs with the Fe3O4 nanoparticles. The fast electrons are captured by the nanoparticles and are converted into slow-charged particles in the NFs, which then reduce the space charge density and result in a more uniform electric field distribution. Streamer propagation in the NFs is also obstructed, and the breakdown strengths of the NFs under impulse voltage conditions are also improved.

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“…Note that only the situation with two crossed λ/4 wave plates is given in equation (10) (11)(12)(13)(14).…”

Section: Deducing the Electric Fieldmentioning

confidence: 99%

“…Moreover, the electric field distribution can hardly be determined in the dielectric bulk, because the electric field cannot be easily calculated from the geometries alone when space charge appears. The Kerr electro-optic space charge measurement method can be used to measure space charge/electric field interactions in high voltage stressed liquid dielectrics [10][11][12][13]. Such as in the early 1980's, Kelley and Hebner [14]] used a CCD array to record the intensity variations, synchronized the detection interval to different times in the waveform, and made some explanation of space charge dynamics.…”

Section: Introductionmentioning

confidence: 99%

“…The measurement system has two main methods, namely, one based on a photodetector and another on line patterns of light maxima and minima measured by a charge-coupled device (CCD). The Kerr measurement system based on a photodetector is used in [13], while the Kerr electro-optic measurement based on line patterns is used to measure space charge distributions in liquids under a DC field, AC field, and pulsed voltage [18][19][20][21]. The Kerr measurement system using a CCD [22] can record fringe patterns that contain dynamic information about the electric field and space charge distribution.…”

Section: Introductionmentioning

confidence: 99%

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Space charge dynamics investigation based on Kerr electro-optic measurements and processing of CCD images

Shi

Yang

Sima

et al. 2013

IEEE Trans. Dielect. Electr. Insul.

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The Kerr electro-optic technique is used to investigate electric field and space charge effects using large Kerr constant propylene carbonate as the dielectric liquid with Kerr constant B≈1.22×10 -12 m/V 2 . However, improved accuracy of this technique to measure space charge distributions remains an important goal. This paper describes inversion algorithm research on obtaining accurate space charge distributions from Kerr measurements. The original charge-coupled device (CCD) image of light intensity was converted into grayscale values for improved calculation. The grayscale CCD image was transformed into the frequency domain through a two-dimensional Fourier transformation. Butterworth filtering techniques were employed for edge enhancement algorithms. The most important parameter for calculation of space charge distributions are the integer fringe numbers n in the sequence of light and dark fringes measured by the CCD camera. Comparison of the improved algorithm and traditional methods for calculating electric field and space charge distributions between a pair of stainless steel parallel plate electrodes was investigated. The space charge dynamics were also calculated after processing the CCD images with some improvements. The results showed the electric field was essentially uniform at early times of pulsed high voltages. This uniformity indicated the absence of space charge during the early transient interval, while a bipolar charge injection was found in the central region between electrodes at later times. For longer times the electric field and space charge distributions slowly became uniform again. Grayscale processing and Butterworth filtering played an important role in the improvement of the algorithm for better image quality and edge enhancement.

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Fundamental property of electric field in rapeseed ester oil based on Kerr electro-optic measurement

Cited by 23 publications

References 10 publications

A comparative study of thermal aging of transformer insulation paper impregnated in natural ester and in mineral oil

A comparative study of thermal aging of transformer insulation paper impregnated in natural ester and in mineral oil

Space charge inhibition effect of nano-Fe3O4 on improvement of impulse breakdown voltage of transformer oil based on improved Kerr optic measurements

Space charge dynamics investigation based on Kerr electro-optic measurements and processing of CCD images

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