Search

The development and utilization of clean energy is becoming more extensive, and wind power generation is one of the key points of this. Occasionally, wind turbines are faced with various extreme environmental impacts such as icing, lightning strikes and so on. In particular, the icing of wind turbines increases icing–wind loads, and results in a reduced power output. And blades broken down lead to large-area shutdown accidents caused by high-speed rotating, which seriously affects the reliability and equipment safety of wind power generation. Relevant institutions and researchers at home and abroad have carried out a lot of research on this. This paper summarizes the formation and influencing factors of wind turbine icing, the influence of icing on wind power generation, and defense technologies. First, it introduces the formation conditions and mechanisms of icing in wind farm regions and the relationship between meteorological and climatic characteristics and icing, and analyzes the key influence factors on icing. Then, the impact of icing on wind turbines is explained from the aspects of mechanical operation, the power curve, jeopardies and economic benefits. And then the monitoring and safety status of wind turbines icing is analyzed, which involves collecting the relevant research on anti-de-icing in wind power generation, introducing various anti/de-icing technologies, and analyzing the principle of icing defense. Finally, this paper summarizes wind turbine icing and its defense technologies, and puts forward the future research direction based on the existing problems of wind power generation icing.

The newly constructed Qinghai-Tibet Railway connecting Golumd and Lhasa is the highest railway in the world, which is located on the hinterland of Qinghai-Tibet Plateau with the average altitude of above 4000 m. Therefore, the external insulation of electric equipments will be affected by the atmospheric conditions in the high altitude regions. In contrast to many test investigations in the artificial climate chamber, there are few ones at the high altitude sites of 3000 m and above. In the paper, the ac artificial pollution tests of four types of composite insulators are carried out at three high altitude sites of 2820 m, 3575 m and 4484 m along the Qinghai-Tibet Railway. The test results show that the ac pollution flashover voltages in high altitude regions are affected not only by the pollution grades but also by the atmospheric parameters. The pollution flashover voltages will decrease with the increase of air pressure but increase with the decreases of ambient temperature. The exponent characterizing the influence of equivalent salt deposit density is 0.26 to 0.32 and the exponent characterizing the influence of non-soluble deposit density is 0.12 to 0.16, the influence of non-soluble deposit density cannot be neglected. The exponent characterizing the influence of air pressure is 0.507 to 0.587. The exponent characterizing the influence of ambient temperature is about 0.20. Considering the combined influence of the air pressure and ambient temperature, the ac flashover voltage of the polluted composite insulators will decrease by 4.0% to 6.4% for the altitude increased per 1000 m. [ABSTRACT FROM AUTHOR]

Abstract-The Qinghai-Tibet Railway is the highest railway in the world. Up to now, there were no test and service data for the external insulation of the power-supply project of the railway system above 4000 m above sea level (a.s.l.). The "g" parameter method recommended by IEC Publication 60.1 (1989) has a limited applicable range. Therefore, based on the former tests carried on the artificial climate chamber (ACC), in this paper, a series of test investigations is conducted on the positive switching impulse (PSI) discharge performance of rod-plane air gaps with gap spacing of 0.25 to 3.0 m at the six high-altitude sites along the Qinghai-Tibet Railway with altitudes of 2820 to 5050 m. With analyses of the mathematical optimization method on the test results, the new correction method of discharge voltage is proposed. They are also checked and compared with the test results obtained from the simulation tests carried out in the ACC. It is indicated that the 50% PSI discharge voltage U[sub50] of the air gap at high altitude is a power function of gap spacing d, also a power function of relative pressure of dry air and absolute humidity. The influence law of atmospheric parameters on U[sub50] obtained at high-altitude sites is the same as that obtained in the ACC. U[sub50]. obtained in the ACC, is about 8.15% higher than that obtained at high-altitude sites due to the influence of nonsimulated factors, such as ultraviolet ray and cosmic radiation. The "g" parameter method is not applicable to the regions with an altitude above 2800 m. [ABSTRACT FROM AUTHOR]

This paper explores the influence of air pressure, temperature and humidity on the switching impulse (SI) flashover performance of different types of clean and dry insulators at different high altitude sites of 2820 m to 5050 m along the Qinghai-Tibet Railway, the highest elevation railway in the world. Seven types of insulators are used in the flashover tests: one is a composite insulator, two are glass insulators and four are porcelain insulators. At the test sites, the ambient temperature varies between 6.7 °C to 28.5 °C and the absolute humidity is between 4.11 g/m³ to 9.69 g/m³. The test results show that the 50% switching impulse flashover voltage of different types of insulators at high altitude sites is independent of the materials and sheds of insulators but has a multi-factor non-linear relation with the shortest arc distance, the dry air pressure, the absolute humidity and the ambient temperature. The relative flashover voltage decreased with the ambient temperature is dependent on the voltage polarity, with 0.152% to 0.165% 1°C for negative SI and 0.099% to 0.108% 1°C for positive SI at the ambient temperature of from 6.7 °C to 28.5 °C. The relative flashover voltage increased with the absolute humidity and is dependent on the air pressure. The higher the altitude is, the more the influence is of the absolute humidity on the flashover voltage of insulators. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Switching impulse discharge performance of air gaps at high altitudes, which is a fundamental in the extremely high voltage external insulation design, remains an unsolved key technology across the world. Due to the limited applicable range of ‘g’ parameter method recommended by IEC Publication 60-1(1989), this paper aims to explore the relationship between positive switching impulse 50% discharge voltage U50 of rod-plane air gaps and atmospheric parameters, and proposes two new voltage correction methods based on the parameter ‘g’ and the atmospheric pressure ratio, respectively. The two methods have been proved by the experimental investigations carried out on 1-m rod-plane air gap both in the artificial climate chamber and at three spots of different high altitudes in this study. The results show that, if the additional influence of absolute humidity is considered, the positive switching impulse 50% discharge voltage U50 of rod-plane air gaps is a power function of relative pressure and relative air density; the ‘g’ parameter method in IEC Publication 60-1(1989) is not applicable to the regions with an altitude above 2000 m or the condition of h/δ > 15 g/m³ compared with the correction method based on the ‘g’ parameter method, the correction method based on relative atmospheric pressure has a wider applicable range and less error; when the absolute humidity increases 1 g/m³, U50 varies within the range of 1.0%–1.15%. [ABSTRACT FROM AUTHOR]