發(fā)布時間：2018-04-30 20:06

  本文選題：換流變壓器 + 脈動直流電壓　； 參考：《重慶大學(xué)》2014年博士論文

【摘要】：換流變壓器是高壓直流輸電系統(tǒng)的關(guān)鍵設(shè)備。與普通電力變壓器相比，換流變壓器的運行工況更為嚴厲，導(dǎo)致?lián)Q流變壓器故障率高于普通電力變壓器。作者針對換流變壓器油紙絕緣可靠性評估的需要，對油紙絕緣脈動直流電壓耐受特性、電老化過程中油紙絕緣空間電荷特性以及油紙絕緣失效模型三個方面的問題進行了深入研究，論文主要內(nèi)容有： ①對油紙絕緣的脈動直流電壓耐受特性及脈動系數(shù)與溫度對油紙絕緣短時耐受電壓和失效時間的影響規(guī)律進行了試驗研究。采用均勻升壓法，在五個溫度下測量了油紙絕緣在脈動直流、交流和直流電壓下的短時耐受電壓，結(jié)合油紙絕緣相對介電常數(shù)和體積電阻率隨溫度的變化規(guī)律，對脈動直流電壓下油紙絕緣短時耐受電壓隨溫度變化的規(guī)律進行了分析；采用恒壓法，測量了油紙絕緣在三種電壓下的失效時間，分析了油紙絕緣失效時間隨電壓和溫度的變化規(guī)律。測量結(jié)果表明，與交流和直流電壓相比，脈動直流電壓下的油紙絕緣電老化特性具有顯著差異。 ②研究了油紙絕緣在脈動直流電壓下電老化過程中的空間電荷變化特性。采用電聲脈沖法測量了電老化油紙試品內(nèi)部空間電荷密度，分析了電老化油紙試品的空間電荷注入、累積、積聚和消散過程，研究了電老化時間和溫度對油紙試品空間電荷匯聚和消散特性的影響。試驗與分析結(jié)果表明，電老化時間的增加和溫度升高，均會導(dǎo)致油紙試品內(nèi)部電荷密度增加，溫度升高使得空間場強畸變更為嚴重。 ③研究了脈動直流電壓下電老化油紙絕緣的空間電荷特征量及其變化規(guī)律，探究了油紙絕緣電老化特性。通過試品內(nèi)部空間電荷密度，計算并對比分析了油紙絕緣空間電荷特征量隨老化時間和溫度變化的規(guī)律，提出了油紙絕緣空間電荷特征量與電老化特性相結(jié)合的分析方法，探究了老化時間和溫度對油紙絕緣電老化特性的影響機制。研究結(jié)果表明，電老化時間的延長加速油紙絕緣老化。溫度的升高增強了電場對油紙絕緣電老化特性的影響。 ④通過分析油紙絕緣失效時間和失效場強威布爾分布的變化規(guī)律，提出了油紙絕緣多風(fēng)險失效模型的構(gòu)建方法，建立了雙變量威布爾失效模型，分析了脈動直流電壓下油紙絕緣電老化失效率的準(zhǔn)確性，提出了油紙絕緣失效率分布的綜合檢驗指標(biāo)反映失效模型估計正確性和精度的評估方法，驗證了雙變量威布爾失效模型的正確性和建模方法的有效性。結(jié)果表明，雙變量威布爾失效模型更有效反映失效場強與油紙絕緣失效率之間的關(guān)系，，提高了失效模型計算結(jié)果的準(zhǔn)確性。 上述研究工作是在換流變壓器閥側(cè)繞組絕緣的電老化特性方面的積極探索，揭示了在脈動直流電壓下老化時間和溫度對油紙絕緣電老化的影響機制。同時豐富了油紙絕緣電老化評估的研究成果，并為換流變壓器油紙絕緣失效診斷以及可靠性評估提供了理論支撐和試驗依據(jù)。
[Abstract]:The converter transformer is the key equipment of the HVDC transmission system. Compared with the ordinary power transformer, the operation condition of the converter transformer is more severe and the fault rate of the converter transformer is higher than the ordinary power transformer. In view of the requirement of the reliability evaluation of the oil paper insulation of the converter transformer, the DC voltage tolerance characteristic of the oil paper insulation pulsation is required. The three aspects of the space charge characteristics of oil paper insulation and the failure model of oil paper insulation in the process of electrical aging are studied in depth.
The influence of pulsating DC voltage tolerance of oil paper insulation and the influence of pulse coefficient and temperature on short-time tolerance voltage and failure time of oil paper insulation is studied. The short-time tolerance voltage of oil paper insulation under pulsating DC, AC and direct current voltage is measured at five temperatures by uniform lift method. The relative dielectric constant and volume resistivity of the oil paper insulation under the pulsating DC voltage are analyzed with the change of temperature with the change of temperature. The failure time of oil paper insulation under three voltages is measured by constant pressure method, and the variation of the failure time of oil paper with voltage and temperature is analyzed. The results show that compared with AC and DC voltage, the electrical aging characteristics of oil paper insulation under fluctuating DC voltage are significantly different.
The change characteristics of space charge in the process of electric aging of oil paper insulation under pulsating DC voltage were studied. The internal space charge density of the test products of electric aging oil paper was measured by electroacoustic pulse method. The space charge injection, accumulation, accumulation and elimination of electrical aging oil paper test products were analyzed, and the electrical aging time and temperature were studied on the test products of oil paper. The experimental and analysis results show that the increase of the electrical aging time and the increase of temperature will result in the increase of the internal charge density of the test products of oil paper, and the temperature increase makes the spatial field strength change seriously.
The characteristic quantity of space charge and the change law of electric aging oil paper insulation under pulsating DC voltage are studied, and the electrical aging characteristics of oil paper insulation are explored. Through the internal space charge density of the test products, the characteristics of the space charge characteristics of oil paper insulation with aging time and temperature are calculated and compared, and the insulation space electricity of oil paper insulation is put forward. The influence mechanism of the aging time and temperature on the electrical aging characteristics of oil paper insulation is investigated by the method of combining the load and the electrical aging characteristics. The results show that the prolonging of the aging time accelerates the aging of oil paper insulation. The increase of temperature enhances the effect of the electric field on the aging characteristics of oil paper insulation.
4. By analyzing the failure time of oil paper insulation and the change law of Weibull distribution of the failure field strength, the construction method of the multi risk failure model of oil paper insulation is put forward, the bivariate Weibull failure model is established, the accuracy of the failure rate of the oil paper insulation under pulsating DC voltage is analyzed, and the distribution of the failure rate of oil paper insulation is put forward. The combined test indexes reflect the correctness and accuracy of the failure model, and verify the correctness of the bivariate Weibull failure model and the validity of the modeling method. The results show that the bivariate Weibull failure model is more effective in reflecting the relationship between the failure field strength and the failure rate of the oil paper insulation, and improves the calculation results of the failure model. Accuracy.
The above research work is an active exploration on the electrical aging characteristics of the insulation of the valve side winding of the converter transformer. It reveals the influence mechanism of the aging time and temperature on the insulation aging of the oil paper under the pulsating DC voltage. It also enriches the research results of the evaluation of the insulation aging of the oil paper insulation and diagnoses the oil paper insulation failure of the converter transformer. It provides theoretical support and experimental basis for reliability evaluation.

【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TM855

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