本文選題：雷電沖擊 + 特快速暫態(tài)過電壓�。� 參考：《太原理工大學》2017年碩士論文

【摘要】：本文主要研究了雷電沖擊電壓和特快速暫態(tài)過電壓(VFTO)在變壓器繞組中的分布。相比于雷電沖擊電壓波,特快速暫態(tài)過電壓的波前時間更短,且由頻譜分析可知,特快速暫態(tài)過電壓包含的頻率更高,所以需要建立不同的模型進行分析。變壓器在變電站中的作用很大,繞組內(nèi)絕緣發(fā)生擊穿后不能自行恢復,所以會造成極大的經(jīng)濟損失�，F(xiàn)在變壓器大部分采用氧化鋅避雷器進行防雷保護,然而避雷器的制作工藝、絕緣老化和惡劣天氣等因素都會影響避雷器的正常動作。此外,實際雷電統(tǒng)計中,變壓器多受雷電入侵的影響,且避雷器經(jīng)常誤動作,所以變壓器的防雷保護不能只靠避雷器,應(yīng)該在繞組內(nèi)部也加強自身的絕緣防護。雷電沖擊電壓波的波前時間為微秒級,其頻率分量主要集中在0~50 kHz,所以以線餅為單位建立了變壓器繞組的等值電路,這樣既保證了計算精度,同時簡化了運算,加快了求解速度;然后求解了等值電路模型中各個元件的參數(shù);最后采用Bergeron等值模型法仿真計算了各種雷電沖擊下變壓器繞組中的過電壓分布。通過實例仿真計算得到,波前時間和波尾時間分別主要影響變壓器繞組的縱絕緣和主絕緣強度;雷電沖擊截波可彌補波前時間延長的缺陷;計及工頻電壓下,當疊加的工頻電壓與標準雷電沖擊電壓的幅值極性相反時,變壓器繞組的過電壓分布情況最嚴重,此時對主、縱絕緣的考核比純標準雷電入侵更加嚴格。此外,還提出了兩種改善變壓器繞組電位分布的措施,即對地電容電流補償和縱向電容補償,并通過實例進行了驗證。特快速暫態(tài)過電壓(VFTO)也是造成變壓器繞組絕緣損壞的原因之一。特快速暫態(tài)過電壓與雷電沖擊過電壓相比,波形陡度大,即波形上升時間為ns級,而雷電沖擊過電壓為μs級。其高頻部分包含的頻率高達50 MHz,極高頻部分高達100 MHz,所以不能采用雷電沖擊下的集中參數(shù)模型。針對特快速暫態(tài)過電壓的特征,建立了變壓器繞組的高頻模型,然后采用頻域法仿真計算了變壓器繞組中的過電壓分布。通過仿真計算得到,在靠近VFTO入侵的前幾段線匝中容易發(fā)生絕緣擊穿,所以應(yīng)加強此處的絕緣防護。
[Abstract]:The distribution of lightning impulse voltage and very fast transient overvoltage VFTO in transformer windings is studied in this paper. Compared with the lightning impulse voltage wave, the wave front time of the very fast transient overvoltage is shorter, and from the spectrum analysis, the frequency of the ultra fast transient overvoltage is higher, so different models should be established to analyze it. The transformer plays a very important role in the substation, and the insulation in the winding can not be recovered by itself after breakdown, so it will cause great economic losses. Nowadays, most transformers use zinc oxide arresters for lightning protection. However, the normal operation of lightning arresters will be affected by the process of making lightning arresters, aging insulation and bad weather. In addition, in the actual lightning statistics, transformers are often affected by lightning intrusion, and lightning arresters often misoperate. Therefore, the lightning protection of transformers should not rely solely on lightning arresters, but should also strengthen their own insulation protection inside the windings. The wave front time of lightning impulse voltage wave is microsecond order, and its frequency component is mainly concentrated at 0 ~ 50 kHz. Therefore, the equivalent circuit of transformer winding is established in the unit of wire cake, which not only guarantees the calculation accuracy, but also simplifies the calculation. The solution speed is accelerated and the parameters of each component in the equivalent circuit model are solved. Finally, the overvoltage distribution in transformer windings under various lightning shocks is simulated by Bergeron equivalent model method. The simulation results show that the wave front time and the wave tail time mainly affect the longitudinal insulation and the main insulation strength of the transformer windings, the lightning impingement truncation can make up the defects of the wave front time extension, and the power frequency voltage is taken into account. When the superposition of the power frequency voltage is opposite to the amplitude polarity of the standard lightning impulse voltage, the overvoltage distribution of the transformer windings is the most serious, and the assessment of the main and longitudinal insulation is more strict than that of the pure standard lightning intrusion. In addition, two measures to improve the potential distribution of transformer windings are put forward, that is, the compensation of the earth capacitance current and the compensation of the longitudinal capacitance. Very fast transient overvoltage (VFTO) is also one of the causes of transformer winding insulation damage. Compared with the lightning impulse overvoltage, the waveform steepness is larger, that is, the rise time of the waveform is ns, and the lightning impulse overvoltage is 渭 s. The frequency of the high frequency part is as high as 50 MHz and that of the very high frequency part is up to 100 MHz, so the centralized parameter model under lightning shock cannot be adopted. According to the characteristics of ultra fast transient overvoltage, the high frequency model of transformer winding is established, and then the over-voltage distribution in transformer winding is simulated by frequency domain method. The simulation results show that insulation breakdown is easy to occur in the first few turns near the VFTO invasion, so the insulation protection should be strengthened here.
【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM41

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本文編號：2039936