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

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.

Polymer insulators using silicone rubber materials as sheds and sheaths are widely used in power systems to replace traditional porcelain and glass insulators which are heavy, inconvenient to install, and prone to pollution flashover. However, in recent years, polymer insulators that have been operating in harsh outdoor environments for many years have experienced different degrees of aging. The aging degree and aging products of silicone rubber are the focus of research. Fourier transform infrared spectroscopy (FTIR) is a technical method to analyze the internal molecular bonds and functional groups of materials, and it is often used to study the aging degree and aging products of silicone rubber. In this paper, the aging characteristics of silicone rubber samples in a high altitude area, salt fog environment, and acid environment were studied by FTIR. The results showed that the silicone rubber in a harsh environment, such as strong radiation, salt fog, and acid fog was degraded to some extent, and its main chain was cut off, the degree of polymerization was reduced, and the content of hydrophobic functional groups was reduced. Infrared spectroscopy can be used to analyze the aging phenomenon of polymers.

In areas with heavy dust or continuous wind in a single direction, fan-shaped nonuniform contamination at the windward and leeward side of the insulator string may affect flashover performance. In this paper, dc pollution flashover tests of insulators under fan-shaped nonuniform pollution were presented, and a comparison of flashover performance among 7-unit suspension insulator strings with four different disk profiles was made. Then, the influence of fan-shaped nonuniform pollution on flashover voltage, arc propagation, and critical leakage distance were investigated. Research results indicate that the insulators with different types were influenced variously on their flashover stress, utilization rate of creepage distance, and critical leakage distance by fan-shaped nonuniform pollution. A reduction in the ratio W/L of windward to leeward side salt deposit density (SDD) from 1/1 to 1/15 gave a median 35% ± 4% decrease in flashover strength. The extrapolation of results for the seven-unit strings suggests that some increment in shed space or structure height of the insulator can be preferable in dc transmission lines where there is fan-shaped nonuniform pollution accumulating at the windward and leeward side of the insulator string.

In recent years, the air particulate pollutants formed by the combustion of fossil fuels and the emission of industrial waste gases have constantly been produced, and the polluted particles deposit also seriously affects social production and people’s lives. For instance, pollution-induced flashover is seriously threatening the safe operation of the power system, while insulator pollution non-uniformity has great influence on the flashover voltage of insulators. Therefore, in this paper both field contamination experiments of HVDC (High Voltage Direct Current) transmission lines and wind tunnel contamination simulation tests were conducted, and pollution non-uniformity coefficient K_T/B, K_W/L and K_H/M were proposed and obtained. The results showed that the degree of contamination on top surface and leeward side is heavier than that on bottom surface and windward side. Thus, in the DC energized condition, contamination along the string is also non-uniform, and serious pollution occurs mainly in the high voltage terminal. In order to explain the uneven distribution phenomenon along the string, the coupling-physics model of composite insulator string was established and using the finite element method, the electric field around the insulator was simulated. Furthermore, basing on the field charging theory, the value of electric field force on particles around the insulator surface was calculated and the mechanism of non-uniformity along the insulator sting was then explained. The results are very important for guiding insulation design and field anti-pollution works.

As a non-contact discharge detection method, ultraviolet (UV) imaging can rapidly, directly, and securely detect corona discharges. Therefore, UV imaging has been widely applied to power systems. To study the influences of different factors on UV corona discharge detection, two typical types of UV imagers (DayCor^®Superb and CoroCAM^®6D) were utilized. Results show that the observation angle has little impact on UV detection if no obstacles block the detection line of sight. Given that different UV imagers have different optimal imager gains, photon numbers under different gains could be calibrated to the values under optimal gains in accordance with the gain correction formula. Photon numbers decrease with the increase in the square of observation distance. Detection results under different observation distances could be corrected to the contrast distance after the detection of electrical equipment. The photon numbers of different UV imager types could be corrected in accordance with the instrumental correction factor. The results of this study can provide references to improve the applications and standardizations of UV imaging technology in corona discharge detection.