Composite insulator why so popular?

by:Mings     2020-04-24
When the composite insulator used in the dc system is, how to choose the suitable distance has become a big problem. At home and abroad on the one hand, it is the result of composite insulator under the dc resistance of fouling resistance model to study too little; On the other hand is due to the dc composite insulator operation experience is also very few, for the product under all kinds of filth corrupt rule is not clear enough, little data is available for reference. Third aspect of the problem is that even under the same uncleanness, porcelain insulator under the positive and negative polarity of lightning pressure also have obvious difference, namely the so-called polarity effect, but also because of the influence of the polarity effect, same shape, the distance of porcelain insulator under the filth of the same degree of the unclean lightning pressure than ac dc voltage RMS lightning is lower, the rectangular ratio less than 1. 0. So in composite insulator used in the dc system when the site choice, need extra attention, should neither appear ac pollution flashover characteristics in accordance with choice of creepage distance caused by the frequent trip, don't blindly increasing creepage distance, too much umbrella skirt too close against insulator self-cleaning, also easy to cause bridging between umbrella skirt, to improve the process of flashing and wet lightning may have little effect, even counterproductive. From the structure to the detailed analysis of the composite insulator composite insulator from the structure to the material is completely different from the traditional porcelain and glass insulator have the following points: (in summary 1) Composite insulator used in the glass steel reinforced bars with axial tensile strength is very high, generally in more than 600 mpa, 5 ~ 10 times that of China, with the strength of high quality carbon steel. In addition, the proportion of core material is only 2. 0, is much lighter than steel: umbrella skirt material proportion is less than 2. 0 and composite insulator can more easily create specified mechanical load the strength level of the hundreds of thousands of cows, quality only disc suspension insulator of 10% ~ 15%. Ultrahigh pressure line in a mountainous area construction and the accident emergency, synthetic insulation to the advantage of light quality, not afraid of falling damage, has been well received by the operation and construction personnel. ( 2) Belong to the composite insulator rod insulator structure, inside and outside almost equal polar distance, generally does not happen internal insulation breakdown, also don't need to detect zero maintenance work. ( 3) Composite insulators umbrella skirt sheath material is organic polymer material, low surface energy, strong hydrophobic. Fall in the water on the surface of the skirt are many tiny water droplets separated from each other, forming a continuous film without conductive layer, and leakage current is small, difficult to form the local electric arc, it is not easy to occur along the surface pollution flashover. Because the mandrel intensity is high, the suspension insulator rod diameter and umbrella diameter is much smaller than the porcelain insulator string, the shape coefficient is big, on the surface dirt and surface conductivity under the same conditions, also the surface resistance is higher than shape coefficient of the porcelain insulator string. Insulator pollution lightning has a direct relationship between pressure and surface resistance, surface resistance is big, small leakage current, corresponding lightning pressure is high. Laboratory test results and running experience has confirmed that the composite insulator pollution flashover performance is high, the pollution flashover accident happens rarely. ( 4) Easy operation maintenance. Impurity cleaning the pollution flashover performance is high, don't have to, and not to detect zero value, the current domestic all kinds of voltage grade of composite insulator are not traditional, heavy cleaning and zero maintenance, greatly reduced the maintenance work.
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