雷电侵入波下牵引变压器绝缘防护研究

发布时间：2018-11-10 23:57

【摘要】：近年来,高速铁路快速发展,其运行安全与电气化铁路牵引供电系统息息相关。牵引变电所在牵引供电系统中占据重要的地位,所内电气设备的绝缘安全备受关注,尤其是作为所内核心设备的牵引变压器,其绝缘状况直接影响变电所的安全运行。研究表明,雷电冲击波侵入牵引变电所后,与所内其他电气设备相比较,变压器上的过电压幅值最高,因此,应对雷击下变压器的绝缘状态进行重点分析。考虑到雷电侵入波本身的特性,即频率范围广、波形幅值高、且持续时间较长,当雷电侵入变压器绕组后,绕组内部复杂的波过程的表现之一为绕组谐振现象。谐振会严重威胁绕组的绝缘安全且外部避雷器保护对谐振的抑制效果不够理想。因此,论文分析了雷电冲击波引起的绕组谐振对牵引变压器绕组绝缘的影响,并提出了绕组并联MOV(Mental Oxide Varistor,金属氧化物压敏电阻)抑制雷电谐振过电压保护绕组绝缘安全的具体方案。主要研究内容如下:首先,就传统变压器绕组多导体传输线模型进行分析,指出实际变压器绕组线匝长度差距较大,而传统传输线模型采用平均匝长求解会造成一定的求解误差。针对这一问题,本文提出了一种改进的绕组环形多导体传输线模型,该模型在极坐标下建模,线匝长度采用绕组实际匝长,并详细推导了该模型的建模过程以及各匝绕组末端电压电流求解公式。其次,详细分析了雷电侵入波下,谐振对绕组绝缘的影响。本文根据建立的环形传输线模型,在频域内推导了绕组传递函数表达式,通过分析绕组幅频特性曲线研究绕组中的谐振情况并对绕组的主要谐振频率以及谐振可能导致的绕组绝缘击穿点进行定位。结果表明:雷电波侵入后,绕组的主要谐振频率在0.8MHz附近且绕组第一饼4匝~8匝线圈绝缘更易因谐振发生击穿,应重点对其进行防护。最后,对雷电侵入下抑制绕组谐振、保护绝缘安全的方案进行研究。本文采用绕组分段并联MOV的方式抑制绕组谐振过电压。分别于10匝、20匝、40匝、60匝绕组之间并接MOV,并对并联MOV后绕组的幅频特性曲线进行仿真分析。结果表明,并接MOV后绕组谐振过电压近乎下降了一半,证明并联MOV的绝缘保护方案具有良好的绕组谐振防护性能。
[Abstract]:With the rapid development of high-speed railway in recent years, its operation safety is closely related to traction power supply system of electrified railway. Traction substation plays an important role in the traction power supply system. The insulation safety of the electrical equipment in the substation is paid close attention to, especially the traction transformer, which is the core equipment in the traction substation, whose insulation directly affects the safe operation of the substation. The study shows that after the lightning shock wave intrudes into the traction substation, the overvoltage amplitude on the transformer is the highest compared with other electrical equipment in the substation. Therefore, the insulation state of the transformer under the lightning strike should be analyzed emphatically. Considering the characteristics of the lightning invading wave, that is, the frequency range is wide, the amplitude of the waveform is high, and the duration is long, one of the complex wave processes in the winding is the winding resonance phenomenon after the lightning intrudes into the winding of the transformer. The resonance will seriously threaten the insulation safety of the winding and the external arrester protection is not good enough to restrain the resonance. Therefore, the paper analyzes the effect of winding resonance caused by lightning shock wave on the winding insulation of traction transformer, and proposes a parallel winding MOV (Mental Oxide Varistor,. Metal oxide varistor) to suppress lightning resonance overvoltage to protect winding insulation safety specific scheme. The main research contents are as follows: firstly, the traditional multi-conductor transmission line model of transformer windings is analyzed, and it is pointed out that the actual transformer winding length gap is large. However, the traditional transmission line model using the average turn length solution will cause a certain solution error. In order to solve this problem, an improved annular multi-conductor transmission line model is proposed. The model is modeled in polar coordinates, and the turn length of the winding is used as the actual turn length of the winding. The modeling process of the model and the solution formula of the voltage and current at the end of each turn winding are deduced in detail. Secondly, the influence of resonance on winding insulation is analyzed in detail. In this paper, the expression of winding transfer function in frequency domain is derived according to the established ring transmission line model. By analyzing the amplitude-frequency characteristic curve of the winding, the resonance in the winding is studied, and the main resonant frequency of the winding and the insulation breakdown point of the winding which may be caused by the resonance are located. The results show that the main resonance frequency of the windings is near 0.8MHz and the insulation of the first 4 ~ 8 turns of the winding is easier to break down because of the resonance after the lightning wave invades. Finally, the scheme of restraining winding resonance and protecting insulation safety under lightning intrusion is studied. In this paper, the winding resonant overvoltage is suppressed by using a piecewise parallel winding MOV. MOV, is connected between 10 turns, 20 turns, 40 turns and 60 turns respectively. The amplitude-frequency characteristic curves of parallel MOV winding are simulated and analyzed. The results show that the resonance overvoltage of the windings is nearly reduced by half after joining the MOV. It is proved that the insulation protection scheme of parallel MOV has good protection performance of winding resonance.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U224.25

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