Investigation on space charge properties of Nomex insulation paper in the mining dry type transformer during hygrothermal ageing

Li, Lu; Song, Jiancheng; Wang, Zhengyu; Zhang, Rui; Cao, Jinmei; Ma, Yixin; Li, Yongzhi

doi:10.1049/iet-smt.2019.0215

Cited by 10 publications

(7 citation statements)

References 21 publications

(17 reference statements)

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“…As a result, the backbone of the benzene ring structure for aramid molecular is broken, which causes the molecular weight of the aramid molecular to decrease, affecting the mechanical properties of the oil-impregnated Nomex paper. [22][23][24][25] Figure 8 shows the content of carbon and oxygen in oilimpregnated Nomex paper based on EDS. It can be seen that the atomic and mass percentage of carbon are the lowest and the atomic and mass percentage of oxygen are the highest for the blank sample.…”

Section: Chemical Properties Analysismentioning

confidence: 99%

“…It can also be observed that the position and shape of the diffraction peaks before and after PD degradation remain basically unchanged, and that only the intensity of the diffraction peak changes. In order to further analyze the influence of high frequency on the aggregation structure of oil-paper insulation, the integral method [23][24][25] has been used to calculate the crystallinity of the paper, as shown in Table II. The corresponding calculation formula is expressed as:…”

Section: Xrd Analysismentioning

confidence: 99%

See 1 more Smart Citation

Surface Degradation of Oil-Immersed Nomex Paper Caused by Partial Discharge of High-Frequency Voltage

Zhang²,

Wang³

et al. 2022

J. Electron. Mater.

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The oil-paper insulation of high-frequency (HF) transformers frequently withstands high-frequency over-voltages at frequencies of several kHz and above. This leads to the occurrence of partial discharge (PD), which causes premature insulation failure in HF transformers. In order to investigate the effect of PD under high-frequency stresses on oil-impregnated Nomex paper, this paper analyzes the surface morphology, bond-broken types of the molecular chain, and product types formed for oil paper after PD degradation. Then, the damage mechanism of oil-immersed Nomex paper between high-frequency and AC stress is explored. The experimental results show that the branches of creepage do not exist in the oil-paper insulation during the entire discharge process under high-frequency stresses, and that their damage degree is higher than that of AC stress. This is mainly because the benzene ring of oil-impregnated Nomex paper is destroyed and opened caused by high-energy particles, the heating effect in HF discharge, and the bulk effect. These results help to improve the design theory of insulation structures and to develop PD-resistant insulation materials in HF transformers.

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Section: Chemical Properties Analysismentioning

confidence: 99%

Section: Xrd Analysismentioning

confidence: 99%

Surface Degradation of Oil-Immersed Nomex Paper Caused by Partial Discharge of High-Frequency Voltage

Zhang²,

Wang³

et al. 2022

J. Electron. Mater.

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“…The space charge transport can be affected by moisture in many aspects. Such as, the increase of moisture content will lead to the decrease of the injection barrier and the increase of trap density, which is conducive to the charge injection [21,22]. In addition, the carrier mobility and negative charge concentration also increase [23].…”

Section: Effects Of Moisture Contentmentioning

confidence: 99%

Effect of multi‐factors on heterocharges for oil‐impregnated paper in converter transformer using modified charge transport model

Yan

Liu

Fan

et al. 2021

IET Generation Trans & Dist

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The heterocharge accumulated in the oil-paper insulation system of the converter transformer will enhance the local electric field and cause insulation deterioration. Numerical simulation is an effective method to analyze heterocharge. Currently, the numerical simulation of heterocharge is mainly based on the bipolar charge transport (BCT) model and the impurity ion transport (IIT) model. However, the effects of temperature, conductivity, and thickness of oil-impregnated paper on charge transport have not been considered in these models. In view of this, a modified charge transport (MCT) model by introducing the Maxwell-Wagner model and heat conduction equation is proposed in this paper based on the BCT model and IIT model. Then, the influence of multi-factors (temperature gradient, moisture content, and oil-impregnated paper thickness) on heterocharge accumulation is investigated by using the MCT model. The simulation results obtained by the MCT model are more consistent with the experimental results than the BCT model, which proves the accuracy and superiority of the MCT model. Moreover, the increase in temperature gradient, moisture content, and oil-impregnated paper thickness will enlarge the ion dissociation rate, conductivity, and trap density, and thus promote the generation of heterocharge. In that respect, the MCT model is expected to optimize the insulation design and provide a reference for space charge dynamic simulation.

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“…At present, dry-type transformer windings mostly adopt organic insulation methods, such as epoxy resin [7][9] [10], NOMEX paper [11] [12], etc. A large number of studies have improved the thermal conductivity and heat resistance of insulation windings for transformers.…”

Section: Introductionmentioning

confidence: 99%

Thermal Analysis and Structure Optimization of a Dry-type Transformer with Ceramic Insulated Windings for Offshore Platform

Wang

et al. 2023

Preprint

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Dry-type transformer is the key hub equipment connecting power generation platform and power consumption platform in marine power system. Partial insulation aging caused by transformer thermal effect is one of the important factors that adversely affect the operation stability. The new ceramic insulation winding prepared by micro-arc oxidation technology has the characteristics of high thermal conductivity and high temperature resistance, and is an ideal product to replace traditional organic insulation materials. Therefore, in this paper, the thermal characteristics and overload capacity of a ceramic insulated aluminum winding dry-type transformer are studied by combining heat flow coupling simulation and experiment. By comparing the temperature field and velocity field characteristics of traditional organic insulated dry-type transformer and ceramic insulated dry-type transformer, the influence of different winding materials on transformer heat dissipation under the same load condition is studied. The hottest spot temperature of ceramic insulated winding dry-type transformer is about 86% of that of traditional organic insulated transformer. The ceramic insulated dry-type transformer has a good overload capacity. Under the premise of meeting the H-class insulation, it can carry 1.4 times the rated load. Finally, the simulation results are compared with the experimental data of the ceramic insulated dry-type transformer. The accuracy of the results was verified.

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Investigation on space charge properties of Nomex insulation paper in the mining dry type transformer during hygrothermal ageing

Cited by 10 publications

References 21 publications

Surface Degradation of Oil-Immersed Nomex Paper Caused by Partial Discharge of High-Frequency Voltage

Surface Degradation of Oil-Immersed Nomex Paper Caused by Partial Discharge of High-Frequency Voltage

Effect of multi‐factors on heterocharges for oil‐impregnated paper in converter transformer using modified charge transport model

Thermal Analysis and Structure Optimization of a Dry-type Transformer with Ceramic Insulated Windings for Offshore Platform

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