Influence of material volume conductivity on electric field and surface charge of RIP valve-side bushing core under DC electro-thermal coupling stress

Chen, Ming; Liu, Xuandong; Sun, Yuhan; Wu, Zhicheng; Tang, Hao

doi:10.1109/tdei.2019.008362

Cited by 17 publications

(9 citation statements)

References 21 publications

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“…To qualitatively analyse the effect of temperature on each energy density type, an electric field strength of 8 kV⋅mm −1 and a frequency of 50 Hz are selected. Based on material parameters proposed by [8,21,22], the variation of each energy density with temperature in the material is obtained in Figure 23.…”

Section: Breakdown Time and Analysismentioning

confidence: 99%

Degradation characteristics of insulation near aluminium foil edges inside dry‐type bushing cores under electrothermal compound stress

et al. 2022

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Insulation breakdown of dry‐type valve‐side bushing cores under electrothermal compound stress has become a key factor limiting the safe and stable operation of the converter transformer. Based on slices of the real bushing core, it is observed for the first time that fold, peeling off, and fracture defects exist near the aluminium (Al) foil edge, accompanied by many metal spikes with a curvature radius <4 μm. Coupled with a capacitor screen thickness of ∼2 mm, an electrical tree model is designed to simulate insulation defects near aluminium foil edges inside dry‐type bushing cores, whose insulation degradation characteristics under electrothermal compound stress are investigated accordingly. The results show that high temperature significantly increases the dielectric loss heat energy density and Joule heat energy density, accelerating the insulation degradation near Al foil edges. The parallel crepe paper interface significantly accelerates the growth of electrical trees under AC‐superimposed positive DC voltage, while this effect is not significant under AC voltage. As the crepe paper consists of wooden fibres of 10 μm diameter, the electrical trees tend to grow along interfaces between fibres and epoxy resin to form “feathery” electrical trees in epoxy resin‐impregnated paper samples.

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Section: Breakdown Time and Analysismentioning

confidence: 99%

Degradation characteristics of insulation near aluminium foil edges inside dry‐type bushing cores under electrothermal compound stress

et al. 2022

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“…Next, we consider the effect of bushing size on the curing process due to the complex curing behavior of the large-volume capacitor core. In this paper, the temperature distribution and stress-strain evolution process of ultra high voltage (UHV) bushing during curing was investigated based on the structural parameters of bushing at 200 kV, 500 kV, 800 kV, and 1100 kV [41][42][43]. The radial temperature difference induced by the accelerator contents became obvious near the 40 h mark.…”

Section: Effect Of Bushing Size On the Curing Processmentioning

confidence: 99%

A Study on Temperature Distribution within HVDC Bushing Influenced by Accelerator Content during the Curing Process

et al. 2022

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Power transmission technology plays an important role in energy sustainability. Bushing is an indispensable type of equipment in power transmission. In production, the accelerator changes the temperature distribution during the curing process, influencing the formation of defects and thus the safety output of renewable energy. In this study, uncured epoxy resin samples with different accelerator contents were prepared and measured by differential scanning calorimetry (DSC). The obtained heat flow curves were analyzed for curing kinetics. Then, the curing process of large length–diameter ratio bushings was simulated by using the finite element method combined with a curing kinetics model, transient Fourier heat transfer model, and stress–strain model. The study reveals that the curing system can be established by the Sestak–Berggren autocatalytic model with different accelerator contents. The overall curing degree and the maximum radial temperature difference of the capacitor core tend to increase and then decrease with the accelerator content. This is mainly attributable to the rapid exotherm excluding the participation of some molecular chains in the reaction, resulting in permanent under-curing. As the accelerator content increases, the strain peak decreases and then increases. This paper provides guidance for the comprehensive evaluation and manufacturing of the low-defect capacitor cores of large-size high voltage direct current (HVDC) bushings.

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“…According to CIGRE group A2/B4.28 [6], insulation failure of the valve side winding and bushings in the converter transformer accounted for 65% of the total failure, which is mainly caused by the insulation damage such as flashovers the surface and dielectric breakdown. From the operation report of the State Grid Corporation of China [7], the failure of the converter valve side bushing accounted for 16.7% of all HVDC equipment failures, which was one of highest fault ratio equipment to cause converter valve lock-up or other insulation failures in converter stations. Thus, it is of great importance to reduce the failure rate of the RIP bushings and improve the reliability of the RIP insulation bushing equipment in the converter transformer.…”

Section: Introductionmentioning

confidence: 99%

Temperature Segment Compensation Method of Dissipation Factor for Insulation Diagnosis in Converter Transformer Bushing

Dai

Liu

et al. 2022

IEEE Access

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Temperature compensation occupies a significant function in the insulation condition evaluation of converter transformer bushings based on the Frequency Domain Spectroscopy (FDS), which could influence the accuracy of its insulation diagnosis. In order to accurately obtain the variation law of FDS at different temperature, a Resin Impregnated Paper (RIP) insulation bushing for converter transformer was designed by the equivalence of maximum electric field, coaxial cylinder structure and RIP materials. The increment law of dielectric parameters both dissipation factor and capacitance at wideband frequency (1mHz ∼ 10kHz) was measured for a quality RIP insulation samples at the temperature from 30 • C to 100 • C. 1) Under the uniform temperature, it was found that the value of dissipation factor was rising with the frequency from 10 Hz to 0.001Hz, while the tendency was reversed at the frequency from 100Hz to10kHz. 2) The minimum value of tanδ from 0.001Hz to 10kHz could be driven to higher frequency moving (10Hz to 10kHz) by the action of temperature rising 30 • C to 100 • C.3) The effect of temperature on the lower frequency 0.001Hz ∼ 1Hz tanδ of RIP insulation closely conformed to the index law of Arrhenius equation, while it was in accordance with the linear decrease at higher frequency 1kHz ∼ 10kHz. The effect of temperature on dissipation factor could be eliminated by curve segment shifting based the experiment equation, which it at 0.001Hz dissipation factor could be eliminated by curve shifting based the index equation originated Arrhenius equation. The method is beneficial to eliminate the influence of temperature on the dielectric spectroscopy test results, and then to eliminate the influence of temperature on the dielectric spectroscopy diagnosis of RIP bushings. INDEX TERMSConverter transformer, resin-impregnated paper insulation, frequency domain spectroscopy (FDS), temperature, dissipation factor, fault diagnosis.

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Influence of material volume conductivity on electric field and surface charge of RIP valve-side bushing core under DC electro-thermal coupling stress

Cited by 17 publications

References 21 publications

Degradation characteristics of insulation near aluminium foil edges inside dry‐type bushing cores under electrothermal compound stress

Degradation characteristics of insulation near aluminium foil edges inside dry‐type bushing cores under electrothermal compound stress

A Study on Temperature Distribution within HVDC Bushing Influenced by Accelerator Content during the Curing Process

Temperature Segment Compensation Method of Dissipation Factor for Insulation Diagnosis in Converter Transformer Bushing

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