共查询到20条相似文献,搜索用时 218 毫秒
1.
<正> 目前电瓷行业对电瓷材料的两项主要电气性能—相对介电常数ε和介质损耗角正切值tanδ的测定,一般都是按GB1409—78《固体电工绝缘材料在工频、音频、高频下介电系数和介质损耗角正切试验方法》,采用高压电桥进行。测量系统的电气原理如图1所示。测量方法是采用三电极(高压电极,测量电极,保护电极)系统。三电极中,测量电极和保护电极之间距——保护间隙宽度和测量时对试品施加的电压大小,对测量结果有一定的影响。电瓷材料测定时,一般试 相似文献
2.
《电瓷避雷器》2017,(1)
电力变压器的内绝缘在雷电过电压的多次冲击下产生累积效应,影响其绝缘性能。研究表明实际雷电入侵波存在双极性衰减振荡波形的情况。首先用不同频率的双极性振荡衰减波波形,取低于其击穿电压的电压值,对油纸绝缘试品进行累积冲击,绘出其V-N特性曲线,验证了累积效应的存在性,探索了V-N特性的规律;继而用宽带频谱介电测试仪对在双极性振荡衰减波作用下累积冲击了100、200、300以及并未受冲击的绝缘纸进行测试,并对比分析了四种情况下复相对介电常数和介质损耗角正切值的变化规律,验证了累积效应对油纸绝缘的损伤。研究结果表明,双极性振荡衰减冲击电压和标准雷电冲击电压对油纸绝缘均存在明显的累积效应。在波形半峰值时间、所施加的电压幅值均相同时,频率越高的双极性振荡波击穿所需的冲击次数越少,复介电常数和介质损耗角正切值均随着累积冲击次数增加而变大,累积效应对油纸绝缘具有损伤。 相似文献
3.
4.
本文对四种电瓷材料在不同温度下(-60℃~+100℃)的相对介电常数、介电常数的温度系数及介质损耗角正切进行了探讨,并通过试验初步取碍了介电常数的温度系数。 相似文献
5.
<正> 1 前言一定条件下绝缘介质中能量损耗的大小是衡量绝缘介质性能的主要指标.在电压作用下,通过介质的电流I包含与电压同相的有功分量I_R及超前电压90°的无功分量I_C.此时介质的功率损耗为P=UI_R=UI_C·tanδ.定义tanδ=I_R/I_C,式中的δ为介质损失角.通常用于测量介质损失角正切的仪 相似文献
6.
《电瓷避雷器》2020,(3)
液体硅橡胶作为电缆附件的组成材料,其密封受潮是电缆发生故障的重要原因之一,因此研究其吸水特性及其对电气性能的影响意义重大。研究了水分子在液体硅橡胶中的扩散模型,温度对水分子扩散过程的影响以及吸水对液体硅橡胶电学性能的影响。结果表明,水分子在液体硅橡胶中扩散过程符合Langmuir扩散模型,而不符合经典的Fick扩散模型,即水分子以"自由态"和"结合态"两种状态存在于在液体硅橡胶中;温度会同时影响水分子扩散进液体硅橡胶和液体硅橡胶中小分子硅氧烷和填料溶解两个过程,所以液体硅橡胶饱和吸水率随温度升高先增大再减小;水的长时间扩散会导致液体硅橡胶损耗角正切增大,电导率增大,工频交流击穿场强降低,相对介电常数增大。 相似文献
7.
8.
《Planning》2014,(33)
本文根据不同树脂的性能采用不同配比制作出环氧树脂/氟树脂复合材料,测量复合树脂的介电常数及介质损耗,并比较不同比例下复合树脂材料的介电常数及介质损耗大小,分析出适用于高频电路板基材的最佳复合树脂比例。 相似文献
9.
10.
为研究温度对环氧胶浸纸绝缘套管频域介电响应特性的影响,开展了环氧胶浸纸绝缘样片在高低温(10℃~120℃)循环下的频域介电谱测试,绘制了不同循环次数下环氧胶浸纸绝缘样片的频域介电响应特性曲线。结果表明:随着高低温循环次数的增加,在120℃时介质损耗因数、复合电容实部和虚部频谱曲线整体向上和高频方向移动,在10℃时在高频区域下介质损耗因数和复合电容虚部的频谱曲线整体向上移动,而复合电容实部的频谱曲线基本保持不变。10℃和120℃频域谱曲线的变化是由于高低温环境限制了环氧胶浸纸单位体积内带电粒子响应速度而造成电导极化作用差异性导致的,而频域谱中高频域的频谱曲线向上移动是由于高低温循环环境使得皱纹纸的纤维素长链裂解和环氧胶的环氧分子分解,致使其内部的极化损耗作用加强导致的。研究结果可为干式环氧胶浸纸绝缘套管状态评估提供一定理论基础。 相似文献
11.
12.
13.
Urban drainage systems that use concrete gutters, pits and pipes have been adopted worldwide by drainage engineers. This study tested the hypothesis that treating a concrete pipe with a coating of epoxy resin is an effective method to reduce the concrete mineral leaching and associated contamination of water carried within the pipe. Four 20 litre samples of rainwater were individually circulated through the untreated and epoxy treated portions of the pipe for 100 minutes. After recirculation through the untreated portion of the pipe pH increased by almost two units, electrical conductivity doubled and there were significant increases in bicarbonate, calcium and other ions. In contrast, rainwater circulated through the epoxy treated portion of the pipe showed a minimal pH increase (0.32 pH units) but no other significant increases in any other water chemistry attributes. The epoxy resin greatly reduced mineral contamination of recirculated water, supporting the hypothesis. 相似文献
14.
J. Šadauskienė V. Stankevičius R. Bliūdžius A. Gailius 《Construction and Building Materials》2009,23(8):2788-2794
The paper aims at the determination of the possible limits of vapour resistance and liquid water permeability alteration in the case of the exterior painted thin-layer render finish of the building walls from outside insulated with the mineral wool slabs when exploited in the area of cold and humid climate that could guarantee a normal moisture state of the wall insulating system. The moisture testing of the insulating system’s fragments was carried out in the climatic chamber, where the climatic parameters were modelled on the basis of the climatic typical of Lithuania. Thin-layer render was coated with acrylic paints. When the thickness of the paint coating on thin-layer render was increased from 0.08 mm to 0.24 mm, the liquid water absorption coefficient decreased by 59% and vapour resistance increased by 43%. It has also been determined that in the double-layer system paint coating – thin-layer render condensation moisture will be accumulated when the thickness of the air layer sd equivalent to the material’s water vapour permeability is higher than 0.6 m. Rain will have an impact on the wall’s moisture state, when the liquid water absorption coefficient w of the double-layer system paint coating – thin-layer render is higher than 0.025 kg/(m2 h0.5). The micro-lens discovered in the areas of moisture accumulation by the thermographic analysis should be considered as the rudiments of the defect formation in the exterior insulating system. 相似文献
15.
FRP加固修复混凝土用粘结材料包括底层涂料、整平腻子和浸渍树脂。底层涂料要求低粘度 ,高浸润性。本实验中介绍了通过不同稀释剂改性环氧树脂后粘度和粘结强度的变化 ,同时针对剪切强度低的现象加入了增韧剂进行了改性后发现 ,不仅环氧树脂粘度高的问题得到了解决 ,固化体系的剪切强度也有了大幅度的提高。 相似文献
16.
17.
针对隧道复杂环境的涂装要求,研制了综合性能优异的水性瓷化防护涂料。通过傅里叶红外光谱确定了水性瓷化涂料的固化工艺;通过调整阻燃剂的用量,研究其对水性瓷化涂料性能的影响,确定配方中氧化镁的添加量为10%。将水性瓷化涂料与市售隧道涂装材料对比,结果表明,水性瓷化涂料的混凝土吸水率低,具有优异的耐沾污、易清洗、耐高低温性能。 相似文献
18.
Ernst L. Back 《Fire Safety Journal》1982,4(3):185-196
This paper summarizes and quantifies experience concerning self-heating and the risk of auto-ignition, due to the absorption of moisture from the surrounding air by low-density bales of hygroscopic cellulosic material such as textiles, waste-paper, and insulating boards during storage. Such risks do exist, especially after a drying operation, and they have apparently led to a number of fires.As a starting-point, the equilibrium moisture content of ligno-cellulosic material over a range of relative humidities and temperatures is presented as well as the heat release accompanying the absorption of water and the condensation of water vapour from ambient air. Using data on the specific heat of cellulosic material, the possible adiabatic temperature rise is calculated. The kinetics of moisture absorption into the bale and the rate of heat transport out of the bale are discussed as a function of the density of the material.It is shown that the heat released by an increase of a few percent. in the moisture content can raise the temperature of low-density hygroscopic material into a range where oxidation rates are sufficient to lead to the onset of carbonization in the centre of the bale. Thereafter, smouldering may lead to auto-ignition. Bales which are not yet ignited often show this carbonization zone in the centre.Preventive measures — such as a controlled remoistening after drying — are summarized. 相似文献
19.
20.
环氧砂浆强度性能研究 总被引:2,自引:0,他引:2
环氧砂浆抗压、抗折等强度是确保环氧地坪涂装体系力学性能的关键因素。本文通过各种环氧树脂固化剂的选择和加砂比例的调节,讨论了影响环氧砂浆强度的各种因素,确定了合适的环氧砂浆施工材料和加砂比例。 相似文献