The ratio <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> / xmlns:xlink="http://www.w3.org/1999/xlink">B</i> of top to bottom surface salt deposit density (SDD) affects the ac pollution flashover performance disk insulator strings. stress was established for fifteen different combinations SDD and T/B in a systematic study, making use seven-unit suspension strings with six profiles this paper. Then comparison made glass porcelain disks same...

Based on the results of experimental investigations performed polluted and iced IEC standard suspension insulator strings 3~21 units, ac flashover performance discharge process are discussed in this paper. It is put forward that icing stress product (ISP), defined as ice-layer conductivity ice layer weight per centimeter dry arc distance can be taken a characteristic parameter to indicate effect accretions contaminants voltage. The an ice-covered string expressed power function ISP has...

Artificial pollution tests have been carried out to study AC flashover performances of various types porcelain, glass, and polymeric insulators in this paper. The experimental results show that the polluted voltage U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> is affected by equivalent salt deposit density rhoESDD nonsoluble rhoNSDD, influences which are independent each other. Based on analyses voltages, correction formulas voltages...

A method is introduced for testing insulators under icing conditions. The based on and developed from those described in the standard of IEC60-1, IEC 60507 IEEE Task Force Insulator Icing Test Methods, which give instructions to test pollution. Then, paper explores effects various factors, including ice thickness, pollution severity surface before accretion, atmospheric pressure, shed profiles, flashover performance short samples two different types silicone rubber (SIR) composite long rod...

Transmission-line icing presents a serious threat to the safe operation of power systems. Therefore, condition overhead transmission lines must be accurately calculated for online monitoring and prewarning Based on data obtained at Xuefeng Mountain Natural Icing Stations (XMNIS), cross-sectional shape glaze conductors was studied, correction coefficient actual nonuniform ice proposed provide an accurate convenient method field measurement. In addition, by analyzing characteristics tension...

Currently, it is founded that under unidirectional wind and certain landform, composite insulators are always fan-shaped non-uniformly polluted. In this paper, artificial pollution tests on three types of with different shed configurations various non-uniform conditions were carried out. Then the flashover performances insulators, porcelain glass compared. Results indicate there a big difference between ac performance non-uninform uninform pollution. The voltage insulator largely influenced...

Ice melting with dc is one of the key technologies to prevent Chinese power grid from ice storms. Especially after severe storm in southern part China early 2008, ice-melting technology has drawn more attention than ever before. However, there are few satisfactory methods select correct parameters so project rarely achieves desired effects some cases when applied Hunan, Guizhou, and other provinces China. Therefore, it great significance develop a method estimate which applicable practical...

Differences in the amount of pollution on top and bottom surfaces an insulator have a great influence DC flashover voltage. Up to now, many investigations been carried out non-uniform performance porcelain glass insulators, but very few composite insulators. In this paper distribution insulators their was analyzed, correction formula for voltage proposed, based artificial tests short samples intended ±800 kV UHVDC. The test results showed that, when ratio (T/B) salt deposit density (SDD)...

In artificial pollution tests, there are three polluting methods frequently used, including quantitative Brushing Method (BM), Dipping (DM) and Spraying (SM). Based on measurements of ac flashover performance four types silicone rubber composite insulators in the climate chamber, this paper studied differences voltage polluted using these methods. The tests show that some characteristics, influences vary specimens different Further, determined by geometry as well degree. However, fitting...

Pollution-induced flashover has a serious threat on the safe and reliable operation of power systems. It is known that pollution voltage directly related to wetting degree layer. But performance characteristics control method layer insulators have not been properly specified in existing test standards. In this paper, processes different types studied an artificial fog chamber. our studies, leakage current surface polluted under environment measured then curves varying with time are plotted....

As natural contamination of insulators may lead to flashover, its determining factors should be studied prevent the occurrence pollution flashover. In this paper, fluid mechanics models with typical shed types were established simulate their flow field distribution and particle collision coefficient (F). At same time, a test lasting for 8 months was carried out in order contrast experimental data simulation results. The research results have shown that: wind velocity type affect near...

Abstract Icing disaster is one of the most serious threats to power grid security in China. This article provides a brief glance current China's monitoring and prevention methods icing (MPI) development status. Despite late start, research on MPI have made outstanding achievements, including formation mechanism causing ice disaster, key technologies characteristics, anti/de‐icing approaches application. It apparent that Chinese scientists engineers confronted worldwide problem anti/de‐icing,...

Abstract The surfaces of lotus leaves with micro- and nano-waxy cuticle structures are superhydrophobic possess a self-healing ability to regain hydrophobicity after damage. Inspired by this phenomenon, the problem water-repellent coatings used in natural environments failing perform damage can be solved if these endowed rapid self-repair self-growth functions. However, there has been almost no exploration into process leaves. changes surface morphology during recovery not understood. There...

Based on the artificial pollution tests, effects of and high altitude flashover performance short samples five kinds UHV/EHV dc composite long rod insulators are analyzed. The exponent characterizing influence salt deposit density voltage is related with profile material insulator shed. values samples' exponents vary between 0.24 0.30, which smaller than those porcelain or glass cap-and-pin insulators, namely, less, relatively. Thus, have certain advantages in severe regions. best ratio...

How to choose external insulation under high altitude, pollution and icing conditions for UHVDC transmission project is a complicated problem. To provide technical reference this engineering roadblock, the dc flashover performance of seven types pre-polluted short samples composite insulators at low air pressure simulated by multifunction artificial climate chamber was researched in paper. The influences ice thickness, on were analyzed. correct formula gradient specimens altitude presented....

The flashover tests of artificially ice-covered composite long-rod insulators, including four types with a nominal voltage 110 kV, 220 kV and 500 were carried out in the multi-function artificial climate chamber. result indicates that, firstly, icing performance improved insulators for regions is not always superior to that standard when light. Meanwhile, E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</sub> (flashover gradient dry arcing...

Observations of contamination tests showed that, the distribution insulators is usually uneven. In this study, solid layer method was used to imitate different non‐uniform pollution conditions and AC flashover 7‐unit were carried out. The results indicate that increase uneven degree J from 1 15 will give a 39% raise U 50 under on top bottom surfaces, 23% decrease for fan‐shaped 21% higher with ring‐shaped pollution. A occupation ratio ( k ) leeward side reduce bigger radius R heavy polluted...

Under continuous wind of single direction, the leeward area insulator string may be polluted more seriously than windward area, making pollution layer distributes like a fan-shape. In this paper, dc flashover tests 7-unit XP-70 with fan-shaped non-uniform were carried out. Then influence on voltage, process, side surface conductivity and resistance discussed. Research results indicate that, ratio W/L to salt deposit density (SDD) affects performance string. A reduction in from 1/1 1/15 would...