【摘要】：全封閉組合電器(GIS)中絕緣介質(zhì)除具有絕緣性能和滅弧性能優(yōu)異的SF6氣體外,還有大量以環(huán)氧樹脂為絕緣介質(zhì)的盆式絕緣子。因為絕緣介質(zhì)的介電常數(shù)會改變電場強度,當(dāng)在電場中放入高介電常數(shù)的材料時,電場強度會有一定量的下降,反之亦然。而介電常數(shù)除了與材料有關(guān)外,還與溫度和頻率有關(guān)。本文以1100kVGIS中的盆式絕緣子為例,分析其介電常數(shù)受頻率變化的影響,以及在雷電和快速暫態(tài)過電壓(VFTO)高頻作用下絕緣子的電氣性能,提高GIS運行的可靠性。雷電沖擊電壓作用下GIS中會產(chǎn)生一個時變場,必須考慮電介質(zhì)中因極化引起的極化電流。本文給出了暫態(tài)電場時域計算模型,考慮了靜態(tài)介電常數(shù)、光頻介電常數(shù)和松弛時間對電場分布的影響,以及高頻下介質(zhì)的物理特性。在雷電沖擊作用下,計算得出不同時刻絕緣子內(nèi)部的電場分布和絕緣子上、下表面的電場分布,為提高絕緣子的可靠性和降低沿面放電發(fā)生機率提供依據(jù)。此外,隔離開關(guān)分合母線時引起的VFTO過電壓,具有幅值高、上升快的特點,波形中包含從幾兆赫茲到幾十兆赫茲的頻率成分。本文給出了GIS中隔離開關(guān)開斷母線充電電流的等值電路并進行了數(shù)值模擬。針對VFTO電壓波的特點,將快速暫態(tài)過電壓進行離散的傅里葉變換,得到波形中主要含有的不同頻譜分量。分析不同頻率分量作用在絕緣介質(zhì)中時,絕緣介質(zhì)的相對介電常數(shù)的變化情況;考慮高頻下絕緣材料的復(fù)介電常數(shù),計算不同頻率分量作用下絕緣子電場,并得出在VFTO作用下的絕緣子內(nèi)部電場分布規(guī)律以及在絕緣子上幾個具體位置的沿面電場分布規(guī)律,找出絕緣子絕緣相對薄弱的環(huán)節(jié)。為了進一步探究絕緣子的介質(zhì)特性,考慮在雷電沖擊電壓作用下,當(dāng)絕緣子介電常數(shù)不同時和各向異性時,對絕緣子電場分布的影響。計算結(jié)果表明,當(dāng)介電常數(shù)不同時盆式絕緣子電場分布的趨勢大致相同,其最大電場強度隨介電常數(shù)的增大而減小;考慮介質(zhì)各向異性時,盆式絕緣子的電場分布與各向同性時相比有很大區(qū)別,所以介質(zhì)的各向異性也應(yīng)是盆式絕緣子絕緣性能的考慮因素之一。
[Abstract]:In (GIS), the insulating dielectric is not only the SF6 gas with excellent insulation and arc extinguishing performance, but also a large number of basin insulators with epoxy resin as the insulating medium. Because the dielectric constant of the insulating medium will change the electric field intensity, when the material with high dielectric constant is added in the electric field, the electric field intensity will decrease by a certain amount, and vice versa. The dielectric constant is not only related to material, but also to temperature and frequency. In this paper, taking the basin insulator in 1100kVGIS as an example, the influence of frequency on the dielectric constant of the insulator is analyzed, and the electrical performance of the insulator under the high frequency action of lightning and fast transient overvoltage (VFTO) is analyzed to improve the reliability of GIS operation. There is a time-varying field in GIS under the action of lightning impulse voltage. The polarization current caused by polarization in dielectric must be considered. In this paper, the time-domain calculation model of transient electric field is presented. The influence of static dielectric constant, optical dielectric constant and relaxation time on the electric field distribution and the physical characteristics of the medium at high frequency are considered. The electric field distribution in the insulator and the electric field distribution on the upper and lower surface of the insulator at different times are calculated under the action of lightning shock, which provides the basis for improving the reliability of the insulator and reducing the probability of the discharge along the surface. In addition, the VFTO overvoltage caused by the separation of the bus bar by the isolator has the characteristics of high amplitude and fast rise, and the waveform contains frequency components ranging from several megahertz to tens of megahertz. In this paper, the equivalent circuit of on-off busbar charging current in GIS is given and the numerical simulation is carried out. According to the characteristics of VFTO voltage wave, the discrete Fourier transform of fast transient overvoltage is carried out, and the main spectral components in the waveform are obtained. This paper analyzes the variation of relative dielectric constant of insulating dielectric when different frequency components act on the dielectric, and calculates the insulator electric field under the action of different frequency components considering the complex dielectric constant of insulating material at high frequency. The internal electric field distribution law of insulator under the action of VFTO and the distribution law of electric field along the surface of several specific positions on insulator are obtained, and the relative weak link of insulator insulation is found out. In order to further explore the dielectric characteristics of insulators, the influence of the dielectric constant and anisotropy of insulators on the electric field distribution of insulators is considered under the action of lightning impulse voltage. The results show that the maximum electric field intensity decreases with the increase of dielectric constant when the dielectric constant is different, and the maximum electric field intensity decreases with the increase of dielectric constant, and when the dielectric anisotropy is considered, the electric field distribution of the basin insulator is approximately the same. The electric field distribution of the basin insulator is different from that of isotropic insulator, so the anisotropy of the dielectric should be one of the factors to consider the insulation performance of the basin insulator.
【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM216;TM595

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