發(fā)布時(shí)間：2018-11-20 08:28

【摘要】：當(dāng)今科學(xué)技術(shù)發(fā)展突飛猛進(jìn),電力是各行各業(yè)前進(jìn)的基礎(chǔ),電力系統(tǒng)的安全供電、經(jīng)濟(jì)送電是安全生產(chǎn)和減少經(jīng)濟(jì)損失的重要保證,因而必須對(duì)電力設(shè)備進(jìn)行有效的保護(hù)。氧化鋅避雷器(簡(jiǎn)稱(chēng)MOA)被廣泛應(yīng)運(yùn)于電力系統(tǒng)中,它與被保護(hù)設(shè)備并聯(lián),當(dāng)雷擊過(guò)電壓發(fā)生時(shí),依靠自身的非線性特性達(dá)到對(duì)電力設(shè)備的保護(hù)。運(yùn)行狀態(tài)的分析判定是確保避雷器正常工作的前提,對(duì)電力設(shè)備甚至整個(gè)電力系統(tǒng)的安全可靠運(yùn)行具有重要的意義。世界各國(guó)對(duì)MOA運(yùn)行狀態(tài)分析的方法很多,如總泄流電流法、基次諧波法、三次諧波法、補(bǔ)償法、雙“AT”檢測(cè)法等。這些方法,雖然能在一定程度上能反映MOA的運(yùn)行狀況,但是檢測(cè)精度不高,甚至造成對(duì)MOA運(yùn)行狀態(tài)的誤判,因此必須對(duì)MOA運(yùn)行狀態(tài)的分析方法進(jìn)行改進(jìn),提高其準(zhǔn)確度。本文在總泄流電流的基礎(chǔ)上利用新閥值平移不變量的小波去噪法,來(lái)抑制傳統(tǒng)閥值去噪法所產(chǎn)生的偽吉布斯現(xiàn)象,從而獲得比較準(zhǔn)確的避雷器全泄露電流信號(hào),并用仿真軟件來(lái)驗(yàn)證方法的有效性,它能精確判斷出MOA晚期老化運(yùn)行狀況,早期和中期老化判斷困難。為了更好的判斷MOA早期和中期老化運(yùn)行狀態(tài),本文研究了基于電容法的改進(jìn)算法,針對(duì)諧波干擾幅值及相位的不確定性,直接測(cè)量總阻性電流可能會(huì)導(dǎo)致MOA運(yùn)行狀態(tài)的誤判,而電容法中沒(méi)有排除諧波電壓對(duì)三次諧波阻性泄漏電流的影響,因而對(duì)電容法進(jìn)行改進(jìn),通過(guò)兩種方法的仿真對(duì)比,分析了不同諧波比重以及不同諧波相位帶來(lái)的影響,各次諧波阻性電流幅值都隨著諧波電壓相位的增大而增大,諧波電壓幅值增大而波動(dòng)增加,兩種算法在基波電阻泄漏電流基本一致,然而用電容法來(lái)分析三次阻性諧波電流,誤差較大,而新算法中,利用電流之間的近似相位關(guān)系,補(bǔ)償了諧波電壓作用下的阻性泄漏電流分量,從而得到基波電壓下的基波阻性電流和三次諧波阻性電流的精確值,從而對(duì)MOA早期和中期有更準(zhǔn)確的判斷。但是當(dāng)避雷器處于晚期老化時(shí),新算法誤差有時(shí)比電容法還大,且測(cè)得的三次諧波阻性電流值變化趨勢(shì)混亂,新算法在此無(wú)效,必須綜合前章的方法來(lái)進(jìn)行避雷器晚期老化的判斷。綜合兩種分析方法,我們可以對(duì)MOA早期、中期和晚期老化進(jìn)行科學(xué)的評(píng)估,對(duì)電力系統(tǒng)安全運(yùn)行有重要意義。
[Abstract]:Nowadays, with the rapid development of science and technology, electric power is the basis of the progress of various industries. The safe power supply of power system and economic power transmission are the important guarantee of safe production and reducing economic losses. Therefore, it is necessary to protect the power equipment effectively. Zinc oxide arrester (MOA) is widely used in power system. It is parallel to the protected equipment. When lightning overvoltage occurs, the protection of power equipment can be achieved by its own nonlinear characteristics. The analysis and determination of operation state is the premise to ensure the normal operation of the arrester, which is of great significance to the safe and reliable operation of the power equipment and even the whole power system. There are many methods to analyze the running state of MOA in the world, such as the total discharge current method, the basic harmonic method, the third harmonic method, the compensation method, the double "AT" detection method and so on. Although these methods can reflect the running status of MOA to a certain extent, the detection accuracy is not high, and even results in misjudgment of the running state of MOA. Therefore, it is necessary to improve the analysis method of running state of MOA to improve its accuracy. In this paper, based on the total discharge current, a new wavelet de-noising method is used to reduce the pseudo-Gibbs phenomenon produced by the traditional threshold de-noising method, so as to obtain the accurate full leakage current signal of the arrester. The simulation software is used to verify the validity of the method. It can accurately judge the running state of late aging of MOA, and it is difficult to judge early and middle aging. In order to judge the early and intermediate aging state of MOA, an improved algorithm based on capacitance method is studied in this paper. In view of the uncertainty of amplitude and phase of harmonic interference, direct measurement of total resistive current may lead to misjudgment of running state of MOA. But the capacitance method does not exclude the influence of harmonic voltage on the third harmonic resistance leakage current, so the capacitance method is improved. Through the simulation and comparison of the two methods, the influence of different harmonic specific gravity and different harmonic phase is analyzed. The amplitude of harmonic resistive current increases with the increase of harmonic voltage phase, and the amplitude of harmonic voltage increases with the increase of harmonic voltage amplitude. The two algorithms are basically consistent in the leakage current of the fundamental resistance. However, the capacitance method is used to analyze the third-order resistive harmonic current. In the new algorithm, the resistance leakage current component under harmonic voltage is compensated by using the approximate phase relation between currents, and the accurate values of the fundamental resistance current and the third harmonic resistance current are obtained. Therefore, the early and middle MOA have a more accurate judgment. However, when the arrester is in the late stage of aging, the error of the new algorithm is sometimes greater than that of the capacitance method, and the measured third harmonic resistive current values tend to change in confusion. The methods in the previous chapter must be integrated to judge the late aging of arresters. By synthesizing two analytical methods, we can scientifically evaluate the early, middle and late aging of MOA, which is of great significance to the safe operation of power system.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TM862

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