110kV和220kV變壓器中性點過電壓仿真分析及其保護探究
發(fā)布時間：2019-03-04 17:28
【摘要】：目前我國110kV和220kV系統(tǒng)變壓器普遍采用部分中性點接地方式運行,變壓器中性點的過電壓保護采取避雷器和放電間隙并聯(lián)措施,但經(jīng)現(xiàn)場運行發(fā)現(xiàn)存在絕緣配合失調(diào)的情況,最常見的故障是系統(tǒng)有效接地時發(fā)生單相接地故障卻引起間隙誤擊穿,導(dǎo)致停電規(guī)模擴大；而棒間隙拒動導(dǎo)致避雷器爆炸和設(shè)備絕緣損壞的事故也多次發(fā)生,亟需進一步完善變壓器中性點的接地方式,保證電力系統(tǒng)安全可靠運行。本文主要基于兩種思路對此問題進行深入探究,第一種是變壓器中性點采用小電抗接地方式,另一種是在目前中性點部分接地方式下,對避雷器和間隙的配合參數(shù)進行整定,并對目前間隙的改進工作提出建議。變壓器經(jīng)小電抗接地運行方式具有防止有效接地系統(tǒng)發(fā)生“失地”現(xiàn)象、限制變壓器中性點短路電流和降低中性點過電壓對系統(tǒng)絕緣損害的優(yōu)勢,且對中性點過電壓的防護,也不再需要裝設(shè)間隙,可有效避免間隙對系統(tǒng)帶來的運行隱患。目前國內(nèi)500kV自耦變壓器中性點經(jīng)小電抗接地方式經(jīng)現(xiàn)場運行檢驗,效果良好,而110kV和220kV變壓器中性點采用經(jīng)小電抗接地方式運行還處在理論完善和現(xiàn)場試驗階段,各文獻對此種方式接地看法不一,有必要對此問題做進一步的研究探討,本文主要研究了系統(tǒng)接入小電抗后變壓器及系統(tǒng)零序阻抗變化,并分析了其對中性點短路電流、系統(tǒng)零序阻抗和變壓器中性點絕緣水平的影響；對接地小電抗的裝置進行了設(shè)計和建議小電抗的取值范圍為變壓器零序阻抗的1/3。本文主要還對目前變壓器中性點采用的部分接地方式進行優(yōu)化和改進。經(jīng)過對多起事故原因的分析研究,發(fā)現(xiàn)中性點處的保護參數(shù)整定應(yīng)依據(jù)變壓器中性點處實際過電壓情況來進行選擇,但目前用作避雷器和間隙整定參考的卻是標(biāo)準(zhǔn)雷電波和工頻電壓波的放電電壓,導(dǎo)致間隙和避雷器不能可靠保護中性點絕緣。本文在考慮了變電所現(xiàn)場運行的各項影響因素后,對在中性點上引起的雷電過電壓和單相接地工頻過電壓的波形情況利用EMTP仿真軟件進行仿真計算,得到的結(jié)論對間隙和避雷器參數(shù)進行整定；然而目前使用的棒間隙仍存在距離調(diào)節(jié)不準(zhǔn)、同心度差和放電分散性高等缺點,其在遭受電弧作用時,電極發(fā)生燒蝕,棒間隙距離發(fā)生變化,使得間隙的使用頻率較低,本文對間隙的改進也提出了自己的建議。
[Abstract]:At present, partial neutral grounding mode is generally used in China's 110kV and 220kV system transformers. The over-voltage protection of transformer neutral points takes measures of lightning arrester and discharge gap parallel. However, it is found that there is a misalignment of insulation coordination in the field operation. The most common fault is that the single-phase grounding fault occurs when the system is effectively grounded, but it causes the gap breakdown by mistake, which leads to the enlargement of the scale of the power outage. The accidents of lightning arrester explosion and equipment insulation damage caused by bar gap rejection also occur many times. It is urgent to further improve the grounding mode of transformer neutral point to ensure the safe and reliable operation of power system. The first is that the neutral point of transformer is grounded by small reactance, and the other is to adjust the matching parameters of lightning arrester and gap under the current partial grounding mode of neutral point, the first is that the neutral point of transformer is grounded by small reactance, and the other is to adjust the matching parameters of lightning arrester and gap under the current partial neutral grounding mode. At the same time, some suggestions are put forward for the improvement of the gap at present. The operation mode of transformer through small reactance earthing has the advantage of preventing the "ground loss" of effective grounding system, limiting the short circuit current of transformer neutral point and reducing the damage of neutral point overvoltage to the insulation of the system, and the protection of neutral point overvoltage. It is no longer necessary to install clearance, which can effectively avoid the hidden trouble caused by clearance to the system. At present, the neutral point of domestic 500kV auto-transformer has been tested by small reactance grounding mode, and the effect is good. However, the neutral point of 110kV and 220kV transformer is still in the stage of perfect theory and field test, while the neutral point of 110kV and 220kV transformer is running through small reactance grounding mode. It is necessary to do further research on this problem. This paper mainly studies the change of transformer and system zero-sequence impedance after the system is connected with small reactance, and analyzes its short-circuit current to neutral point. The influence of the zero sequence impedance of the system and the insulation level of the transformer neutral point; The small reactance device is designed and suggested that the value range of the small reactance is 1 / 3 of the zero sequence impedance of the transformer. This paper also optimizes and improves the partial grounding method used in transformer neutral point at present. Through the analysis of the causes of many accidents, it is found that the setting of the protection parameters at the neutral point should be based on the actual over-voltage at the neutral point of the transformer. However, the discharge voltage of standard lightning wave and power frequency voltage wave is the reference of lightning arrestor and clearance setting at present, which leads to the unreliable protection of neutral point insulation. After considering the influence factors of substation operation, this paper uses EMTP simulation software to simulate the waveform of lightning overvoltage and single-phase-to-earth power frequency overvoltage caused by neutral point. Finally, the parameters of clearance and arrester are adjusted. However, the gap of rod used at present still has the shortcomings of wrong distance adjustment, poor concentric degree and high dispersion of discharge. Under the action of arc, the electrode is ablative and the distance of rod gap is changed, which makes the use frequency of the gap lower. This paper also puts forward some suggestions for the improvement of gap.
【學(xué)位授予單位】：山西大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM41
本文編號：2434472
[Abstract]:At present, partial neutral grounding mode is generally used in China's 110kV and 220kV system transformers. The over-voltage protection of transformer neutral points takes measures of lightning arrester and discharge gap parallel. However, it is found that there is a misalignment of insulation coordination in the field operation. The most common fault is that the single-phase grounding fault occurs when the system is effectively grounded, but it causes the gap breakdown by mistake, which leads to the enlargement of the scale of the power outage. The accidents of lightning arrester explosion and equipment insulation damage caused by bar gap rejection also occur many times. It is urgent to further improve the grounding mode of transformer neutral point to ensure the safe and reliable operation of power system. The first is that the neutral point of transformer is grounded by small reactance, and the other is to adjust the matching parameters of lightning arrester and gap under the current partial grounding mode of neutral point, the first is that the neutral point of transformer is grounded by small reactance, and the other is to adjust the matching parameters of lightning arrester and gap under the current partial neutral grounding mode. At the same time, some suggestions are put forward for the improvement of the gap at present. The operation mode of transformer through small reactance earthing has the advantage of preventing the "ground loss" of effective grounding system, limiting the short circuit current of transformer neutral point and reducing the damage of neutral point overvoltage to the insulation of the system, and the protection of neutral point overvoltage. It is no longer necessary to install clearance, which can effectively avoid the hidden trouble caused by clearance to the system. At present, the neutral point of domestic 500kV auto-transformer has been tested by small reactance grounding mode, and the effect is good. However, the neutral point of 110kV and 220kV transformer is still in the stage of perfect theory and field test, while the neutral point of 110kV and 220kV transformer is running through small reactance grounding mode. It is necessary to do further research on this problem. This paper mainly studies the change of transformer and system zero-sequence impedance after the system is connected with small reactance, and analyzes its short-circuit current to neutral point. The influence of the zero sequence impedance of the system and the insulation level of the transformer neutral point; The small reactance device is designed and suggested that the value range of the small reactance is 1 / 3 of the zero sequence impedance of the transformer. This paper also optimizes and improves the partial grounding method used in transformer neutral point at present. Through the analysis of the causes of many accidents, it is found that the setting of the protection parameters at the neutral point should be based on the actual over-voltage at the neutral point of the transformer. However, the discharge voltage of standard lightning wave and power frequency voltage wave is the reference of lightning arrestor and clearance setting at present, which leads to the unreliable protection of neutral point insulation. After considering the influence factors of substation operation, this paper uses EMTP simulation software to simulate the waveform of lightning overvoltage and single-phase-to-earth power frequency overvoltage caused by neutral point. Finally, the parameters of clearance and arrester are adjusted. However, the gap of rod used at present still has the shortcomings of wrong distance adjustment, poor concentric degree and high dispersion of discharge. Under the action of arc, the electrode is ablative and the distance of rod gap is changed, which makes the use frequency of the gap lower. This paper also puts forward some suggestions for the improvement of gap.
【學(xué)位授予單位】：山西大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM41
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，本文編號：2434472
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