本文選題：變壓器油 + Kerr電光效應(yīng)�。� 參考：《重慶大學(xué)》2014年博士論文

【摘要】：電力變壓器作為電力系統(tǒng)中能量轉(zhuǎn)換和傳輸?shù)暮诵脑O(shè)備，其安全穩(wěn)定運(yùn)行關(guān)系著人們正常的生活和國(guó)家的經(jīng)濟(jì)命脈，由操作沖擊導(dǎo)致的內(nèi)絕緣放電將帶來(lái)嚴(yán)重的后果。變壓器油是一種絕緣性能優(yōu)良的液體電介質(zhì)，并已在電力變壓器中廣泛應(yīng)用，隨著我國(guó)特高壓電網(wǎng)的快速發(fā)展，電力系統(tǒng)電壓等級(jí)不斷增加，為了節(jié)省生產(chǎn)成本的和空間資源，變壓器本身逐漸緊湊化，這進(jìn)一步增加了變壓器絕緣的設(shè)計(jì)與制造難度；同時(shí)，變壓器油中不可避免地存在空間電荷，空間電荷的出現(xiàn)不一定引起擊穿，但能夠通過(guò)畸變場(chǎng)強(qiáng)，影響變壓器油的擊穿強(qiáng)度。因此，需要從變壓器油本身出發(fā)，提高其絕緣性能，這對(duì)提升變壓器的絕緣水平和保障電力系統(tǒng)的安全運(yùn)行具有重要的工程和理論研究?jī)r(jià)值。 本文開(kāi)展了變壓器和納米改性變壓器油中電場(chǎng)和空間電荷分布的測(cè)量工作，對(duì)納米改性變壓器油的操作沖擊擊穿特性進(jìn)行了試驗(yàn)研究、仿真模擬與理論分析。主要研究?jī)?nèi)容和相應(yīng)的結(jié)論有： ①以高Kerr常數(shù)碳酸丙烯酯液體為載體，，分析了其中空間電荷分布的Kerr電光測(cè)量系統(tǒng)、測(cè)量原理，探索了液體中電場(chǎng)-光強(qiáng)圖的成像規(guī)律，研制的Kerr電光測(cè)量系統(tǒng)為變壓器油中電場(chǎng)和空間電荷分布的測(cè)量奠定了基礎(chǔ)。為了提高電光測(cè)量的精度，對(duì)光路進(jìn)行了優(yōu)化以消除電場(chǎng)等傾線的干擾，得到了一種規(guī)范的空間電荷分布的測(cè)量系統(tǒng)及其反算方法。并最終利用該系統(tǒng)測(cè)量并得到了操作沖擊電壓下碳酸丙烯酯液體中空間電荷的注入水平及其分布的動(dòng)態(tài)過(guò)程，其中CCD（Charge Coupled Device，電荷耦合元件）圖像的灰度化處理和頻域?yàn)V波等技術(shù)提高了液體中空間電荷的計(jì)算精度。對(duì)碳酸丙烯酯液體中空間電荷注入與輸運(yùn)過(guò)程進(jìn)行了仿真，與試驗(yàn)測(cè)量結(jié)果對(duì)比后發(fā)現(xiàn)雙電層理論和電化學(xué)反應(yīng)過(guò)程分別能夠很好地解釋液體中空間電荷的注入與產(chǎn)生機(jī)理。 ②基于高Kerr常數(shù)碳酸丙烯酯液體中空間電荷的測(cè)量方法和數(shù)據(jù)處理方法，利用陣列型光探測(cè)量了低Kerr常數(shù)純變壓器油和納米改性變壓器油在操作沖擊電壓作用下的電場(chǎng)和空間電荷分布。試驗(yàn)發(fā)現(xiàn)平板不銹鋼電極系統(tǒng)下的納米改性變壓器油的耐受電壓比純變壓器油的高8.3%，利用陣列型光探測(cè)量結(jié)果解釋了納米變壓器油的耐受電壓提高的原因，即不銹鋼平板電極間納米改性變壓器油中的雙電極同性電荷注入現(xiàn)象更加明顯，電極附近的電荷注入水平更高（純變壓器油和納米改性變壓器油空間電荷水平分別為0.010C/m3和0.036C/m3），空間電荷的屏蔽作用更好，從而使納米改性變壓器油具有更高的耐壓特性。 ③研究了納米改性變壓器油中納米粒子的自然穩(wěn)定機(jī)制和被充電后的納米粒子在電場(chǎng)作用下的遷移過(guò)程，對(duì)納米粒子進(jìn)行了表面改性試驗(yàn)、油中納米粒子的分散性測(cè)試，結(jié)果表明，自然狀態(tài)下經(jīng)表面改性后的納米粒子能夠穩(wěn)定的分散在變壓器油中，直流電場(chǎng)下納米粒子容易吸附到正電極，交流和操作沖擊電壓下的納米改性變壓器油中的納米粒子也是穩(wěn)定的。對(duì)介電型（Al2O3）、半導(dǎo)體型（TiO2）和導(dǎo)電型納米粒子（Fe3O4）改性的變壓器油在操作沖擊電壓作用下的擊穿特性進(jìn)行了測(cè)試，并與傳統(tǒng)變壓器油的擊穿特性進(jìn)行對(duì)比，結(jié)果表明，Al2O3、TiO2、Fe3O4納米改性變壓器油的正極性操作沖擊擊穿電壓較純油分別提高了35.9%、33.3%、44.3%，而負(fù)極性操作沖擊下變壓器的擊穿電壓分別只提高了11.5%、10.2%、8.12%，提高幅度較小。 ④從導(dǎo)電型納米粒子與介電型納米粒子在外加電場(chǎng)下的界面電荷特性入手，分析了它們對(duì)電子載流子的捕捉作用，得到了不同介電特性納米粒子對(duì)流注發(fā)展過(guò)程影響的普適性規(guī)律，即不論是導(dǎo)電型納米粒子還是介電型的納米粒子，在電場(chǎng)作用下，其界面分別形成的感應(yīng)電荷和極化電荷，都會(huì)產(chǎn)生電荷勢(shì)壘，吸附變壓器油擊穿過(guò)程中流注中的電子，從而降低流注發(fā)展速率，提高了變壓器油的擊穿電壓水平。納米粒子對(duì)電子吸附的飽和電量與其電導(dǎo)率和介電常數(shù)有關(guān)，每個(gè)Al2O3、TiO2、Fe3O4納米粒子分別能吸附的電子數(shù)為7.9e、11e、11.4e。 ⑤基于對(duì)變壓器油中電荷載體的注入、產(chǎn)生、消失、復(fù)合、遷移等過(guò)程的理論分析和參數(shù)的確定，建立了變壓器油中流注放電發(fā)展的場(chǎng)致分子電離模型，基于該模型得到的流注尺寸和流注發(fā)展速率與試驗(yàn)結(jié)果吻合，同時(shí)得到了流注通道內(nèi)的電場(chǎng)、空間電荷、電位、溫度分布等參數(shù)。納米改性變壓器油中納米粒子對(duì)流注中電子的捕捉作用降低了流注發(fā)展速率和限制了流注尺寸，且流注頭部的正離子、負(fù)離子、電子及空間電荷密度都有所提高，而流注通道中只有電子密度相對(duì)純油中流注通道是降低的，原因是納米粒子對(duì)電子的捕獲作用降低了流注頭部的電子數(shù)密度，為了維持流注的進(jìn)一步發(fā)展，流注頭部更多的中性分子會(huì)被電離。 上述研究工作，為新型變壓器油的研制提供了試驗(yàn)支持和理論依據(jù)，有利于大型電力變壓器的內(nèi)絕緣優(yōu)化設(shè)計(jì)。
[Abstract]:Power transformer is the core equipment of energy conversion and transmission in power system. The safe and stable operation of power transformer is related to people's normal life and national economic lifeline. The internal insulation discharge caused by operation impact will bring serious consequences. Transformer oil is a kind of liquid dielectric with excellent insulation performance and has been in power transformer. With the rapid development of the UHV power grid in China, the voltage level of the power system is increasing. In order to save the production cost and the space resources, the transformer itself is gradually compact, which further increases the difficulty of the design and manufacture of the transformer insulation. At the same time, the space charge and space charge inevitably exist in the transformer oil. The appearance of the transformer does not necessarily cause breakdown, but it can affect the breakdown strength of transformer oil through the distortion field strength. Therefore, it is necessary to improve the insulation performance from the transformer oil itself, which is of great engineering and theoretical value for improving the insulation level of the transformer and ensuring the safe operation of the power system.
In this paper, the measurement of electric field and space charge distribution in transformer and nano modified transformer oil is carried out. The operation impact breakdown characteristics of nano modified transformer oil are studied, simulation and theoretical analysis are carried out. The main research content and the corresponding conclusions are as follows:
(1) using the high Kerr constant propylene carbonate liquid as the carrier, the Kerr electro-optic measurement system of the space charge distribution is analyzed, the measurement principle and the imaging law of the electric field intensity map in the liquid are explored. The developed Kerr electro-optic measurement system has laid the foundation for the measurement of the electric field and the space charge distribution in the transformer oil. The optical path was optimized to eliminate the interference of the electric field. A standard space charge distribution measurement system and its inverse method were obtained. Finally, the dynamic process of the injection level and distribution of the space charge in the propylene carbonate liquid under the operating impact voltage was measured and obtained, in which CCD (Cha) Rge Coupled Device, the gray-scale processing of the charge coupled element and the frequency domain filtering techniques have improved the calculation precision of the space charge in the liquid. The space charge injection and transport process in the propylene carbonate liquid is simulated. Explain the injection and generation mechanism of space charge in liquid.
(2) based on the measurement method and data processing method of space charge in high Kerr constant propylene carbonate liquid, the electric field and space charge distribution of low Kerr constant pure transformer oil and nano modified transformer oil under operating impact voltage are measured by array type optical probe. The nano modification of the plate stainless steel electrode system is found in the experiment. The tolerance voltage of the transformer oil is 8.3% higher than that of the pure transformer oil. The reason for the increase of the tolerance voltage of the nano transformer oil is explained by the result of the array optical probe measurement, that is, the double electrode same-sex charge injection phenomenon in the nano modified transformer oil between the stainless steel plate electrodes is more obvious, and the charge injection level near the electrode is higher (pure variable pressure). The space charge level of the oil and nano modified transformer oil is 0.010C/m3 and 0.036C/m3 respectively. The shielding effect of space charge is better, which makes the nano modified transformer oil have higher pressure resistance.
The natural stability mechanism of nano particles in the nano modified transformer oil and the migration process of the charged nanoparticles under the action of the electric field are studied. The surface modification of the nanoparticles and the dispersion test of the nanoparticles in the oil have been tested. The results show that the surface modified nanoparticles can be dispersed steadily in the natural state. In the transformer oil, the nanoparticles are easy to adsorb to the positive electrode in the DC electric field. The nanoparticles in the nano modified transformer oil under the shock voltage are also stable. The breakdown characteristics of the transformer oil of the dielectric type (Al2O3), the semi conductor (TiO2) and the conductive nano particles (Fe3O4) modified by the operating impulse voltage The results show that the impact breakdown voltage of Al2O3, TiO2, Fe3O4 modified transformer oil is increased by 35.9%, 33.3%, 44.3% respectively compared with the pure oil, and the breakdown voltage of transformer is increased by 11.5%, 10.2%, 8.12%, respectively. Smaller.
(4) from the interface charge characteristics of conductive nanoparticles and dielectric nanoparticles under the applied electric field, the capture effect of them on the electron carrier is analyzed. The universal law of the influence of different dielectric properties on the flow development process is obtained, that is, whether the conductive nanoparticles or the dielectric nanoparticles are in the field. Under the action of the electric field, the induction charge and the polarized charge formed by the interface respectively produce the charge barrier, which adsorb the electrons in the flow injection during the breakdown of the transformer oil, thus reducing the rate of the flow development and improving the breakdown voltage level of the transformer oil. The saturation of the electron absorption by the nanoparticles is related to the electrical conductivity and dielectric constant. The number of electrons adsorbed by each Al2O3, TiO2 and Fe3O4 nanoparticles is 7.9e, 11e, 11.4e., respectively.
Based on the theoretical analysis and parameters determination of the injection, generation, disappearance, recombination, migration and other processes of charge carrier in transformer oil, a field induced molecular ionization model for the development of streamer discharge in transformer oil is established. The flow size and speed of flow injection based on this model coincide with the experimental results. At the same time, the flow channel is obtained in the flow channel. The electric field, space charge, potential, temperature distribution and other parameters. The capture effect of the electrons in the nanoparticles in the nano modified transformer oil reduces the rate of flow development and limits the flow size, and the positive ion, negative ion, electron and space charge density of the flow head are improved, while only the electron density in the flow channel is relative to the flow. The flow channel in pure oil is reduced because the electron capture of nanoparticles reduces the number density of the electron in the head of the flow. In order to maintain the further development of the flow injection, more neutral molecules on the head of the streamer will be ionized.
The above research work provides experimental support and theoretical basis for the development of new transformer oil, and is conducive to the optimization design of internal insulation for large power transformers.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM41

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