【摘要】：近年來,高速鐵路快速發(fā)展,其運行安全與電氣化鐵路牽引供電系統(tǒng)息息相關。牽引變電所在牽引供電系統(tǒng)中占據重要的地位,所內電氣設備的絕緣安全備受關注,尤其是作為所內核心設備的牽引變壓器,其絕緣狀況直接影響變電所的安全運行。研究表明,雷電沖擊波侵入牽引變電所后,與所內其他電氣設備相比較,變壓器上的過電壓幅值最高,因此,應對雷擊下變壓器的絕緣狀態(tài)進行重點分析。考慮到雷電侵入波本身的特性,即頻率范圍廣、波形幅值高、且持續(xù)時間較長,當雷電侵入變壓器繞組后,繞組內部復雜的波過程的表現之一為繞組諧振現象。諧振會嚴重威脅繞組的絕緣安全且外部避雷器保護對諧振的抑制效果不夠理想。因此,論文分析了雷電沖擊波引起的繞組諧振對牽引變壓器繞組絕緣的影響,并提出了繞組并聯(lián)MOV(Mental Oxide Varistor,金屬氧化物壓敏電阻)抑制雷電諧振過電壓保護繞組絕緣安全的具體方案。主要研究內容如下:首先,就傳統(tǒng)變壓器繞組多導體傳輸線模型進行分析,指出實際變壓器繞組線匝長度差距較大,而傳統(tǒng)傳輸線模型采用平均匝長求解會造成一定的求解誤差。針對這一問題,本文提出了一種改進的繞組環(huán)形多導體傳輸線模型,該模型在極坐標下建模,線匝長度采用繞組實際匝長,并詳細推導了該模型的建模過程以及各匝繞組末端電壓電流求解公式。其次,詳細分析了雷電侵入波下,諧振對繞組絕緣的影響。本文根據建立的環(huán)形傳輸線模型,在頻域內推導了繞組傳遞函數表達式,通過分析繞組幅頻特性曲線研究繞組中的諧振情況并對繞組的主要諧振頻率以及諧振可能導致的繞組絕緣擊穿點進行定位。結果表明:雷電波侵入后,繞組的主要諧振頻率在0.8MHz附近且繞組第一餅4匝~8匝線圈絕緣更易因諧振發(fā)生擊穿,應重點對其進行防護。最后,對雷電侵入下抑制繞組諧振、保護絕緣安全的方案進行研究。本文采用繞組分段并聯(lián)MOV的方式抑制繞組諧振過電壓。分別于10匝、20匝、40匝、60匝繞組之間并接MOV,并對并聯(lián)MOV后繞組的幅頻特性曲線進行仿真分析。結果表明,并接MOV后繞組諧振過電壓近乎下降了一半,證明并聯(lián)MOV的絕緣保護方案具有良好的繞組諧振防護性能。
[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.
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U224.25

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