脉动直流电压下油纸绝缘电老化特性与双变量威布尔失效模型研究

发布时间：2018-04-30 20:06

本文选题：换流变压器 + 脉动直流电压　；参考：《重庆大学》2014年博士论文

【摘要】：换流变压器是高压直流输电系统的关键设备。与普通电力变压器相比，换流变压器的运行工况更为严厉，导致换流变压器故障率高于普通电力变压器。作者针对换流变压器油纸绝缘可靠性评估的需要，对油纸绝缘脉动直流电压耐受特性、电老化过程中油纸绝缘空间电荷特性以及油纸绝缘失效模型三个方面的问题进行了深入研究，论文主要内容有： ①对油纸绝缘的脉动直流电压耐受特性及脉动系数与温度对油纸绝缘短时耐受电压和失效时间的影响规律进行了试验研究。采用均匀升压法，在五个温度下测量了油纸绝缘在脉动直流、交流和直流电压下的短时耐受电压，结合油纸绝缘相对介电常数和体积电阻率随温度的变化规律，对脉动直流电压下油纸绝缘短时耐受电压随温度变化的规律进行了分析；采用恒压法，测量了油纸绝缘在三种电压下的失效时间，分析了油纸绝缘失效时间随电压和温度的变化规律。测量结果表明，与交流和直流电压相比，脉动直流电压下的油纸绝缘电老化特性具有显著差异。 ②研究了油纸绝缘在脉动直流电压下电老化过程中的空间电荷变化特性。采用电声脉冲法测量了电老化油纸试品内部空间电荷密度，分析了电老化油纸试品的空间电荷注入、累积、积聚和消散过程，研究了电老化时间和温度对油纸试品空间电荷汇聚和消散特性的影响。试验与分析结果表明，电老化时间的增加和温度升高，均会导致油纸试品内部电荷密度增加，温度升高使得空间场强畸变更为严重。 ③研究了脉动直流电压下电老化油纸绝缘的空间电荷特征量及其变化规律，探究了油纸绝缘电老化特性。通过试品内部空间电荷密度，计算并对比分析了油纸绝缘空间电荷特征量随老化时间和温度变化的规律，提出了油纸绝缘空间电荷特征量与电老化特性相结合的分析方法，探究了老化时间和温度对油纸绝缘电老化特性的影响机制。研究结果表明，电老化时间的延长加速油纸绝缘老化。温度的升高增强了电场对油纸绝缘电老化特性的影响。 ④通过分析油纸绝缘失效时间和失效场强威布尔分布的变化规律，提出了油纸绝缘多风险失效模型的构建方法，建立了双变量威布尔失效模型，分析了脉动直流电压下油纸绝缘电老化失效率的准确性，提出了油纸绝缘失效率分布的综合检验指标反映失效模型估计正确性和精度的评估方法，验证了双变量威布尔失效模型的正确性和建模方法的有效性。结果表明，双变量威布尔失效模型更有效反映失效场强与油纸绝缘失效率之间的关系，，提高了失效模型计算结果的准确性。上述研究工作是在换流变压器阀侧绕组绝缘的电老化特性方面的积极探索，揭示了在脉动直流电压下老化时间和温度对油纸绝缘电老化的影响机制。同时丰富了油纸绝缘电老化评估的研究成果，并为换流变压器油纸绝缘失效诊断以及可靠性评估提供了理论支撑和试验依据。
[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.

【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM855

【参考文献】