复合绝缘子老化评估方法浅析

复合绝缘子老化是用户十分关心的问题。笔者介绍了两种判别复合绝缘子老化程度的方法,并通过实例,分析了这两种方法的优点以及存在的问题。     

Flashover voltage characteristics of contaminated station insulators under temporary ac overvoltages in the ac system connected with a frequency converter station

According to the recent analysis results of temporary ac overvoltage in the ac system connected with a frequency converter station, large-magnitude over-voltages were confirmed to occur under some special system conditions. Most of the station insulators currently used cannot withstand such overvoltages according to an evaluation based on the data obtained earlier. The necessity of tests to be done to evaluate such performance more accurately was recognized. Both power frequency and switching impulse overvoltage flashover tests were made on contaminated insulators by the method well simulating the natural wetting condition. Switching impulse flashover voltage with the waveshape having a long wavefront time of 2 ms can be well correlated with the flashover voltage characteristics of temporary ac overvoltage. Higher flashover voltage characteristics were obtained by a clean fog test method compared with those obtained by equivalent fog test method.     

Effective lightning protection schemes for distribution line

The causes of lightning outage are subdivided into direct lightning strokes and induced lightning strokes, which are identified by the characteristics of the lightning overvoltage. In the past, lightning protection devices were directed mainly toward the latter, and attention has been focused on the installation of lightning protection devices, ground wires, and reinforcement of insulators. However, lightning outages continue to occur. Thus it is extremely important to clarify the fault characteristics of lightning surges and to study the effectiveness of various lightning protection devices by considering both direct lightning stroke and induced lightning stroke in order to prevent lightning outage in the future. In this research, the electromagnetic transients program (EMTP) has been applied to the direct lightning stroke, and the induced lightning outage analysis program for multiple conductor systems has been applied to the induced lightning stroke to study the effectiveness of lightning protection devices provided by combination of various lightning protection devices. The most effective lightning protection schemes are analyzed and evaluated based on verification tests on the full scale models as well as economic considerations.     

复合绝缘子耐电腐蚀特点及其电蚀老化区域性的差异

为了了解复合绝缘子外绝缘材质电蚀老化状态和区域性的差异,对Al(OH)3耐电腐蚀机理、外绝缘材质中Al(OH)3颗粒分布状态和环境污湿因素的实际情况进行了研究。Al(OH)3颗粒分解成水蒸气、析出白色粉末状氧化铝,并催化生成二氧化碳,将使外绝缘材质逐渐微观减薄和加大表面的粗糙度,而引起电蚀老化的污湿环境因素,近期不可能得到改善,因此必然引起其电蚀老化出现区域性差异。此外,外绝缘憎水表面污珠场强变化引起的电晕也是促使电蚀老化的重要因素。     

Estimating room temperatures from fires along walls and in corners

Determination of temperatures associated with room fires provides a means of assessing an important aspect of fire hazard: the likelihood of the occurrence of flashover. Layer temperatures in excess of 600°C have been associated with the occurrence of flashover. A data correlation has previously been presented to estimate layer temperatures for fires burning in the center of rooms. For fires in corners and along walls, restricted entrainment results in higher layer temperatures than predicted by the previous correlation. Modification factors for the previous correlation are developed to extend its applicability to wall and corner burning geometries. The present analysis suggests that a fire in a corner may cause flashover with only half the heat release rate necessary for a fire burning in the center of a room. Reference: Frederick Mowrer and Robert Williamson, Estimating Room Temperatures from Fires along Walls and in Corners,Fire Technology, Vol. 23, May 1987, pp. 133–145.     

Electronic Theory of Thermodynamic Adhesion inMetal/Ceramic Systems

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电除尘器绝缘子的设计与选择

根据电除尘器绝缘子的功能、工况条件等特点，分别从材质、外形尺寸等方面介绍了设计和选择的注意事项。为用户合理地选择电除尘器绝缘子提供了帮助。     

电除尘器绝缘子的设计与选择

根据电除尘器绝缘子的功能及工况条件，介绍了材质和结构形式的选择。对于电除尘器绝缘子材质的选择，首先要考虑承受运行电压的能力，其次是耐温性能和机械强度。对于结构形式的选择，应考虑有足够的厚度以耐电力冲击、足够大的爬电距离以防漏电或对地闪络、足够大的空间以防出现电晕或空间闪络。另外，介绍了高铝瓷绝缘子的成功应用及其优点。     

低密度泡沫玻璃的研究与应用

低密度泡沫玻璃是利用碎玻璃制造的一种气孔率大于90%的隔热保温材料,它具有强度高、导热系数小、吸水率低、不吸湿、耐腐蚀等特性,在潮湿环境下抗冻性能好,是一种优良的低温、超低温隔热保温材料。该产品用途广泛,所用的原材料简单易得,但生产工艺过程比较复杂,生产过程控制精度要求较高,容易产生各种缺陷而影响产品的质量。本文对低密度泡沫玻璃的生产工艺过程进行详细的分析研究,提出相应的措施,确保产品的低密度和高成品率,提高产品的性能,扩大产品的使用范围。     

硅橡胶在电气绝缘方面的应用进展

简述了国内外硅橡胶(高温硫化型硅橡胶、室温硫化型硅橡胶、液体硅橡胶等)在电气绝缘方面的应用情况。