【作者】 周利军；

【导师】 吴广宁；

【作者基本信息】 西南交通大学 ， 电气系统控制与信息技术， 2007， 博士

【摘要】 电气化铁道向着重载运输和高速客运专线方向发展,对牵引供电设备的绝缘提出了更高要求。同时“对牵引供电设备实施状态检修和寿命管理的必然趋势”要求对其绝缘破坏机理及状态监测等有深入研究。目前关于牵引变压器绝缘老化及引起老化的因素等均未见系统报道。论文研究了具有冲击性、不平衡性和非线性的牵引负荷对变压器两大绝缘老化因素(变压器内部温升、油纸中微水扩散)的影响,同时研究基于油中溶解气体分析的变压器状态预测方法。用基于电热模拟原理的热路法研究不平衡负荷下三相-两相牵引变压器(我国最常用的YNd11接线牵引变压器和Scott接线牵引变压器)的绕组温升计算和温升特点;采用流体力学和热传输原理建立了油流或绕组的动量方程、能量平衡方程以及热传输方程研究冲击负荷下牵引变压器绕组温升特点,分析其热点温升频繁过冲的产生机理:变压器负荷急剧增加时,油流速度缓慢增大,油道中热量不能及时散发,导致油道温度及绕组热点温度产生过冲;以投入运行的变压器为例,研究温升对牵引变压器绝缘老化的影响。根据已发布实验数据,采用基于参数拟合的分区域曲面拟合法获取任意温度下油纸绝缘微水稳态分布曲线;采用Fick第二扩散定理推导简单结构油纸绝缘微水扩散的暂态分布函数为时间常数变化的指数函数,通过仿真分析可知温度、绝缘厚度、稳态浓度及透水方式与时间常数之间互相独立;根据牵引变压器绝缘结构特点,并考虑牵引负荷下绝缘老化所产生的微水,建立了牵引变压器油纸绝缘微水扩散的数学模型;根据这一模型,提出了基于模型的牵引变压器绝缘纸中微水浓度监测方案。研究绝缘油中溶解气体在线监测的关键技术及故障预测方法。在线监测技术研究中,重点研究用于检测故障气体的半导体传感器的检测模型,提出了关于传感器响应与恢复特性的三个假设:传感器稳态输出电阻的对数与气体浓度的对数服从正切关系,暂态响应特性取决于传感器当前的阻值状态和当前时刻的气体浓度,恢复特性取决于传感器当前阻值状态和下一时刻的气体浓度,实验表明检测模型有效。故障预测采用两种手段:先预测气体浓度的变化情况,再根据预测所得气体判断故障的发展,预测过程中,考虑了各故障气体浓度增长时的相互制约关系,提出了用灰色预测法进行初步预测,用自学习神经网络进行修正的方法;根据历史数据建立多个故障隶属度时间序列,再通过预测各故障时间序列的变化情况推测变压器故障的发展。更多还原

【Abstract】 The insulation of the traction power supply equipment is demand more reliable with the development of the high-speed passenger transportation line, and the heavy-loaded train transportation. At the same time, since the condition maintenance and life management are the developing trend, it is urgent to study on the insulation ageing, insulation failure mechanics, insulation condition monitoring and so on for the traction power supply equipments. But there are few reports about insulation ageing factors of traction transformer. It is found there are three characters for loads in traction transformer, i.e., impact properties, asymmetry, and non-linearity, affecting the insulation ageing factors, e.g., temperature rise, and disequilibrium moisture partition of oil-paper insulation.Two thermal circuits are developed for calculating and analyzing the inner temperature rise in ungrounded-wye delta traction transformer and Scott connected traction transformer, in order to minish the temperaure rise calculation error under anisomerous loads. And by employing heat transfer principles and hydrodynamics, another model for hot-spot temperature rise in non-directed flow windings has been developed to explain the thermal overshoot phenomenon for step changes in load, as occurs in traction transformers, in which the duct oil flow velocity is taken into account, and it is validated using experimental results obtained for step changing load current on a 40-MVA-ONAN-cooled unit. According to the developed model as applied to two transformer units (20MVA and 40MVA), the hot spot temperature rise overshoots because of the change in duct flow velocity lags the change in power dissipation after the change in load, and the overshoot factor is larger with larger difference between the initialized and steady velocity.A surface function for the temperature, the moisture in oil, and the moisture in paper is proposed, using the existed curves at the different temperatures, according to which, the equilibrium moisture partition curves in oil-paper insulation at arbitrary temperatures can be obtained. The method is validated by comparing the calculated curve and the published experiment data. And then a transient moisture equilibrium model of oil-paper insulation is designed using Fick’s second law, which is validated by experiment. By the model, the transient moisture concentration at the coordinate in the direction of the thickness is obtained, and then average moisture concentration of paper is calculated, on basis of analyzing the affects of the temperature, the equilibrium concentration, the thickness of the paper and the penetrating mode of moisture on the equilibrium time. And by the model, a model based monitoring technique for moisture in oil-paper insulation of the traction transformer is proposed.Three hypotheses about steady-state responding, transient responding and resuming behavior of semiconductor gas sensor used in on-line monitoring system for dissolved gases in transformer oil insulting oil, according to which, the logarithm of the steady-state resistance value and the logarithm of the gases concentration obey to tangent function, the transient responding is decided by the current resistance of the sensor and the gases concentration, and the resuming behavior is decided by the current resistance of the sensor and gases concentration at the next time. The hypotheses have been validated by experiment.Two methods have been used for predicting insulation faults in transformer. In the first method, the gases concentrations are predicted firstly by grey model, and then the results will be calibrated by self-learning BP-neural networks, on basis of analyzing the affects of different types of gases each other, as well as the relationship of time sequences made up of fault gases. In the second method, the faults relative membership degrees are predicted using time series analysis technique based on gray theory, and the the faults are diagnosed by an improved threshold value principle. The two methods have been validated by analyzing history datum.更多还原