提高绝缘子的可靠性及其降低成本的技术进展

论文介绍了2001年世界绝缘子大会的概况，就会议论文与报告，从生产、应用以及有待解决的问题等方面，评述了绝缘子、芯棒、硅橡胶、憎水性涂层等产品的新技术与新进展，并提出了我国绝缘子行业中存在的问题和努力的方向。     

SnO2压敏陶瓷掺杂MnO2的制备和性能研究

采用MnO2部分替代ZnO的方法固相烧结制备了SnO2-ZnO Ta2O5基压敏陶瓷。研究了Zn,Mn共同掺杂对SnO2微观结构和电学性能的影响,发现少量Mn的替代掺杂可以改善SnO2压敏陶瓷的非线性并显著提高其电压梯度。当MnO2的摩尔分数为0.25%时,样品的非线性达到了21.37,电压梯度为422 V/mm,泄漏电流为72.12 μA/cm2。造成这种变化的主要原因是Mn补充了SnO2晶格中ZnO原有的不溶部分,通过固溶反应产生了受主缺陷离子Mn″Sn,增大了受主浓度,促进了势垒的形成。同时,Mn在SnO2晶格中的溶解度较低,容易在晶界层析出,阻碍晶粒生长,增加了电压梯度。     

变压器现场局部放电缺陷查寻及原因分析

局部放电测量技术作为检验电气设备内部绝缘好坏的有效手段得到越来越普遍的应用。采用“多端测量 ,多端校正”及电气一超声联合测试 ,可准确发现并确定现场安装后的电力变压器内部存在的缺陷及其位置。试验结果表明 ,在现场进行电力变压器的局部放电试验 ,对提高安装质量 ,防止设备损坏及保证电网的安全运行将会起到积极的作用。     

低温等离子体处理粉尘中二恶英的初步研究

对低温等离子体处理粉尘中的二恶英初步研究的结果显示 ,正脉冲放电对粉尘中二恶英的处理效果较负脉冲放电的处理效果好。对不同毒性当量因子的二恶英同分异构体进行试验后发现脉冲放电对二恶英同分异构体的处理效率不同。一般来说 ,二恶英毒性越高 (毒性当量因子越大 )的同分异构体 ,用脉冲放电处理的效果越好 ,毒性当量因子最大的 2 ,3,7,8- T4 CDD分解效率最高 ,可达到 81%。     

Characterization and comprehension of corona partial discharge in air under power frequency to very low frequency voltage

For the partial discharge test of electrical equipment with large capacitance, the use of lowfrequency voltage instead of power frequency voltage can effectively reduce the capacity requirements of test power supply. However, the validity of PD test under low frequency voltage needs to be evaluated. In order to investigate the influence of voltage frequency on corona discharge in the air, the discharge test of the tip-plate electrode under the frequency from 50 to 0.1 Hz is carried out based on the impulse current method. The results show that some of the main features of corona under low frequency do not change. The magnitude of discharge in a positive half cycle is obviously larger than that in a negative cycle. The magnitude of discharge and interval in positive cycle are random, while that in negative cycle are regular. With the decrease of frequency, the inception voltage increases. The variation trend of maximum and average magnitude and repetition rate of the discharge in positive and negative half cycle with the variation of voltage frequency and magnitude is demonstrated, with discussion and interpretation from the aspects of space charge transportation, effective discharge time and transition of discharge modes. There is an obvious difference in the phase resolved pattern of partial discharge and characteristic parameters of discharge patterns between power and low frequency. The experimental results can be the reference for mode identification of partial discharge under low frequency tests. The trend of the measured parameters with the variation of frequency provides more information about the insulation defect than traditional measurements under a single frequency (usually 50 Hz). Also it helps to understand the mechanism of corona discharge with an explanation of the characteristics under different frequencies.     

直流电场下低密度聚乙烯纳米介质空间电荷特性的数值分析(英文)

The dynamic characteristics of space charge in nanocomposite of low-density polyethylene (LDPE) mixed with inorganic nano- fillers. Different from previous qualitatively theoretical works, we investigated the influence of trap depth, trap volume charge density and injection barrier height on the space charge and the electric field distribution in the nanocomposite under a DC external electric field (100 MV/m) systematically and quantificationally, through numerical simulations based on a bipolar charge transport model. The simulation re- sults showed that, the increase of trap depth would severely distort the balanced electric field distribution with the highest and the lowest electric field of 119 MV/m and 47 MV/m, respectively. It is concluded that the introduction of nanofillers creates more deep traps, which would block space charges by capturing most of them in the vicinity of electrode and hence reduce the local electric field largely. Further theoretical analysis of the simulation indicates that both the high permittivity and the low local electric field of the nanocomposite contri- buted to the increase of injection barrier height, and almost no charge could overcome an injection barrier higher than 1.25 eV. At last, a mechanism of space charge suppression in the LDPE nanocomposite was presented.     

合成绝缘子交流转轮法与斜面法的比较研究

转轮法即将成为IEC62217试验方法,该法比综合气候加速老化试验方法的试验设备简单,试验周期短。 硅橡胶合成绝缘子交流转轮法试验结果表明,转轮法在一定程度上可筛选有问题的合成绝缘子,但主要仍是考核 试品的耐漏电起痕性能,而就这一考核而言斜面法的严酷性要高于转轮法。     

电场分量对交直流复合电场下油纸绝缘沿面放电特性的影响

油纸绝缘沿面放电现象与绝缘纸板表面的电场分布关系密切,因而使用无背面电极和有背面电极两种结构,研究了电场分量对交直流复合电压下油纸绝缘沿面放电特性的影响机制。研究结果表明:随着直流电压分量的不断增加,油纸绝缘的沿面闪络电压逐渐上升,且交流电压下的闪络电压最低;无背面电极结构下沿面闪络电压无极性效应,有背面电极结构中存在极性效应,且负极性直流电压分量作用下,由于纤维素中羟基的强电负性影响,致使沿面闪络电压较低;无背面电极结构时的闪络电压约为有背面电极结构时闪络电压的1.5倍,分析认为由于载流子受到强垂直电场分量作用,加剧了对绝缘纸板表面的碰撞,油纸绝缘空间电荷平衡状态易在较低交流电压分量作用下受到扰动而被破坏,进而诱发沿面闪络发生,致使沿面闪络电压逐渐下降,该下降趋势具有饱和现象;沿面闪络在交流电压分量接近波峰或者波谷位置处发生。     

空间电荷对油纸绝缘体击穿强度和沿面闪络的影响

换流变压器是直流输电工程的核心设备之一,其结构和工作状况比传统交流变压器更为复杂。针对换流变压器的特点,设计了相应的试验装置,初步对油纸绝缘中的体击穿和沿面闪络进行了试验研究。试验结果表明,极性反转现象同样存在于油纸绝缘系统中。即在直流电压下油纸绝缘中积聚的空间电荷畸变了周围的电场,导致油纸绝缘的直流击穿强度发生改变。同时,对油纸绝缘进行的沿面闪络试验表明,空间电荷的存在同样会影响油纸绝缘的沿面闪络。通过对上述试验结果进行讨论,发现传统交流变压器的设计理论和经验已不能满足换流变压器的要求,在换流变压器设计和制造中应给予空间电荷问题足够的关注。     

基于介电和理化特性的XLPE水树老化程度分析

为掌握电缆水树老化程度对电缆主绝缘介电特性的影响规律,对交联聚乙烯(cross-linked polyethylene,XLPE)开展加速水树老化试验,以低密度聚乙烯为对照组,测量不同老化程度试样的介电常数(ε)、介质损耗因数(tanδ)、结晶度以及熔点等特征参量,并利用显微技术观测XLPE水树的生长特性。结果表明:XLPE材料的ε和低频下tanδ随水树老化程度加深而呈现增大的趋势。水树在发展过程中呈现放射状,且密集度不断增加。建立XLPE材料的tanδ宏观参量与微观水树老化发展的对应关系,可通过低频下电缆主绝缘材料XLPE的tanδ值评估电缆水树老化的严重程度。