Natural contamination test of insulators with DC voltage energization at inland areas

Equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) are two basic parameters for the coordination of outdoor insulation and classification of pollution severity. Type XP-70 is usually selected as the test object for classification of pollution distribution in China. In this study, 113 transmission towers representing typical distribution of Shenzhen, China, are selected as observation sites for XP-70 insulators, which have a total of four discs. The ESDD, NSDD and the ratio of NSDD to ESDD for XP-70 insulators with the exposure times of one, two and three years are measured. The following aspects are compared: the difference of natural contamination characteristics of four XP-70 insulators at the same place, the difference of natural contamination characteristics of XP-70 insulators in five different regions (the coastal region, the highway region, the suburb region, the mountain region, and the urban region), and the difference of natural contamination characteristics of XP-70 insulators after years of contamination exposure. The results are as follows: the difference between the ESDD and NSDD of the upper surface of the four discs is significant, whereas that of the lower surface is not. The contamination in the coastal region is the most severe whereas that in the mountain region is the lightest. For the rest three regions, the difference is negligible. The ESDD and NSDD of XP-70 insulators become saturated at different times. We also found that presence of the vulcanized silicone rubber (RTV) coating will significantly increase the ESDD and NSDD of the insulators.

Section: Introductionsupporting

confidence: 63%

Section: The Natural Contamination Characteristics Of the Xp-70 Insulmentioning

confidence: 90%

The natural contamination of XP-70 insulators in Shenzhen, China

Wang

Zhou

et al. 2016

“…For SDD of 0.05 mg/cm 2 , E L of Type E is 0.31 kV/cm at the altitude of 232 m while 0.26 kV/cm at the altitude of 2500 m. E L of Type E is computed at 0.29 kV/cm at the altitude of 1000 m, then the 50% withstand voltage gradient along the leakage distance U′ 50 (in kV/m) is 27.0 kV/m at SDD of 0.05 mg/cm 2 and the altitude of 1000 m based on equation (6). So the basic leakage distance of 30.2 m also can be obtained by the above equations (7) and (8).…”

Section: Discussionmentioning

confidence: 99%

“…[3] shows that the ratio of the pollutant which accumulated on dc insulators to those on ac insulators is 1-3 and the ratio of the pollutant on the top surface to those on the bottom surface of dc insulators is 1/3-1/20. Under the same pollution and wetting conditions, the dc pollution flashover voltages are 20%-30% lower than those of ac because of the effect of the steady dc arc without zero point, moreover, the dc pollution flashover voltages will decrease more than ac voltages with the increase of the pollution degree [4][5][6].…”

Section: Introductionmentioning

confidence: 92%

Study on Pollution Flashover Performance of Short Samples of Composite Insulators Intended for /spl plusmn/800 kV UHV DC

Jiang

Yuan

Zhang

et al. 2007

Based on the artificial pollution tests, the effects of pollution and high altitude on the flashover performance of short samples of five kinds of UHV/EHV dc composite long rod insulators are analyzed. The exponent characterizing the influence of salt deposit density on the flashover voltage is related with the profile and the material of the insulator shed. The values of the samples' exponents vary between 0.24 and 0.30, which are smaller than those of porcelain or glass cap-and-pin insulators, namely, the influence of the pollution on the composite long rod insulators is less, relatively. Thus, the composite insulators have certain advantages in severe pollution regions. The best ratio of the leakage distance to the arcing distance is about 3.35. The exponent characterizing the influence of air pressure on the flashover voltage is related with the profile and the material of the insulator shed and the pollution severity, the values of the samples' exponents vary between 0.6 and 0.8, which are larger than those of porcelain or glass cap-and-pin insulators. Therefore, the dc composite insulator used in high altitude regions should have enough arcing distance. Based on the test results, if insulator sample Type E is selected for the ±800 kV UHV dc transmission lines, the basic arcing distance should be no less than 8.16 m and the basic leakage distance no less than 30.2 m.

“…All these lines pass through the high altitude regions, for example, 95% lines of Nuozhadu-Guangdong ± 800 kV project in Yunnan province run through areas with an altitude of 600 to 2000 m, while the rest are higher than 2000 m. There is a great deal of research that shows pollutants accumulate on insulators are more and pollution flashover voltages of insulators are lower for dc condition than those for ac [2,3], and flashover voltages decrease with the increasing of altitudes [1]. Therefore, it is important and urgent to study the pollution flashover performance of HVDC transmission-line insulators at high altitude sites.…”

Section: Introductionmentioning

confidence: 97%

Artificial pollution flashover performance of porcelain long rod UHVDC insulators at high altitudes

Yang

Hao

et al. 2014

Porcelain long rod insulators are recommended for outdoor insulation of UHV/EHV dc transmission lines because of their excellent service experience obtained in Central Europe. However, very few studies have been conducted on dc pollution flashover performance or the UHVDC insulators at high altitudes. Artificial pollution tests on 300 kN and above porcelain long rod insulators were carried out with dc voltage in natural high altitude areas (about 2000 m), in which the solid layer method was used and the 50% flashover voltage (U 50% ) was measured with the up-and-down method. Test results show that dc pollution flashover performances of the 300 and 400 kN insulators are similar. The exponents characterizing influence of salt deposit density on the flashover voltage vary from 0.46 to 0.57. A nearly linear relationship between the flashover voltage and the string length of the insulators is presented. Both double suspension strings and tension string patterns have a significant influence on the flashover voltage. The influence of non-uniform pollution distribution between the top and bottom surfaces of the insulator sheds on the flashover voltage is analyzed, and a correction coefficient for the insulators is proposed.