Pollution Flashover Characteristics Research Articles

Research on Insulation Configuration of 220 kV Bushing in High-Altitude Polluted Areas

The external insulation strength of the power equipment sleeve in the substation and converter station will be reduced with the increase in altitude and atmosphere pollution. The weakness of external insulation seriously threatens the safe operation of electrical equipment. At present, there are few studies and conclusions that focus on the flashover characteristics of power equipment bushing in high-altitude polluted areas. Therefore, this paper takes the 220 kV voltage level bushing as the research object and studies the Alternating Current (AC) pollution flashover characteristics and lightning and switching impulse flashover characteristics at low pressure. The insulation configuration at high-altitude polluted areas is analyzed. Finally, the insulation configuration scheme, which is suitable for high-altitude polluted areas, is proposed. The results show that the AC pollution flashover voltages of the bushing decrease with the decrease in the atmospheric pressure and the increase in the salt density as a power exponent function. The impulse flashover voltages also decrease with the decrease in the atmospheric pressure as a power exponent function. The atmospheric pressure/pollution impact characteristic index is related to the type of voltage, the value of the atmospheric pressure, and the value of the salt density. The test bushing does not meet the insulation configuration requirements in some high-altitude polluted areas. Through the analysis and calculation of the test results, the bushing insulation configuration scheme in high-altitude polluted areas is proposed. The research results can provide a reference for the external insulation design of bushings in substations and converter stations in high-altitude polluted areas.

Flashover characteristics and altitude correction of railway insulators at high altitude and polluted areas

The reduction of electrical performance of railway insulators at high altitude and polluted areas affects the safe operation of the railway. A lot of studies have been carried out on transmission line insulators at home and abroad, but whether the results can guide the design of railway insulators has not yet been determined. This paper takes the railway insulator QBG-25/16 as the research object, experimentally studied the lightning impulse and AC pollution flashover characteristics of the railway insulator under low air pressure, analyzed its insulation configuration under high altitude and pollution environment, and finally proposed its altitude correction method. The results show that the flashover voltages of the insulator decrease in a power function as the air pressure decreases, and decrease in a power function as the salt deposit density increases, and the air pressure influence characteristic index and pollution influence characteristic index are related to voltage type, air pressure and salt deposit density. The tested insulators do not satisfy the requirements for insulation strength at certain high altitude and polluted areas. Finally, the altitude correction method for railway insulators is given. The results of the study provide guidance for the selection of external insulation for electrified railway systems at high altitude.

Optimized Design of Shed Parameters for Polluted Hollow Porcelain Insulators at High Altitude

The pollution flashover problem of hollow insulators, one of the primary faults in substations, can be improved by optimizing the shed parameters. Combining the artificial pollution test and electric field simulation, this paper studies the optimal shed parameters for 220 kV hollow porcelain insulators at high altitudes. The AC artificial pollution flashover test was conducted by solid-layer and up-and-down methods in the artificial climate chamber to analyze the pollution flashover characteristics of the 220 kV hollow porcelain insulator at various altitudes and pollution degrees. After the validity of the artificial pollution flashover test and the direction of optimization of the shed parameters were clarified, electric field simulation was implemented on a two-dimensional axisymmetric model to analyze the effects of shed spacing and large shed overhang on the electric field distribution of the insulator. Based on the pollution flashover characteristics and the simulation analysis results, we find that appropriately increasing the shed spacing and reducing the large shed overhang can improve the surface electric field distribution of the hollow porcelain insulator, thereby improving its pollution flashover characteristics.

Pollution Flashover Characteristics of Composite Crossarm Insulator with a Large Diameter

The composite crossarm insulator differs greatly from the suspension insulator in structure and arrangement. This study aims to determine the pollution flashover characteristics of composite crossarm insulators under different voltage grades. Four types of AC composite crossarm insulators with diameters ranging from 100 mm to 450 mm are subjected to artificial pollution test, and then the effects of the surface hydrophobicity state of silicone rubber, core diameter, umbrella structure, arrangement, and insulation distance on the pollution flashover voltage of the composite crossarm insulators are analyzed. Under the pollution grade 0.2/1.0 mg/cm2 and voltage grade from 66 kV to 1000 kV, if the silicone rubber surface changes from HC5 to HC6, the pollution flashover voltage of the composite crossarm insulator will increase by 13.5% to 21.0% compared with the hydrophilic surface. If the core diameter changes from 100 mm to 300 mm, the pollution flashover voltage gradient decreases with the increase in core diameter; if the core diameter changes from 300 mm to 450 mm, the pollution flashover voltage gradient increases with core diameter. Under the same insulation height and core diameter, the umbrella structure will have a certain impact on pollution flashover voltage by up to 1.7% to 5.4%. Under the horizontal arrangement, the pollution flashover voltage can increase by 10.5% to 12.1% compared with that under the vertical arrangement. Under the hydrophilic surface and weak hydrophobicity state, the pollution flashover voltage has a linear relationship with the insulation distance. The above results can provide a reference for the structural design and optimization of the composite crossarm insulator.

Pollution Flashover Characteristics of Coated Insulators under Different Profiles of Coating Damage

Based on experiments and numerical analysis techniques, this paper aims to investigate the influence of the four different coating damage profiles on the performance of coated 33 kV porcelain insulator strings under polluted and clean surface conditions. The performance of the insulators coated with room temperature vulcanizing (RTV) under partial coating damage and undamaged coating was evaluated. The influence of humidity on pollution flashover was taken into consideration. The ring-shaped, fan-shaped, and random-shaped coating was applied following coating damage. The results showed that the flashover characteristic of the RTV-coated insulators had a significant difference as compared to the normal insulators. Electrical characteristics such as the flashover voltage, critical current, and surface resistance were significantly affected by coating damage distribution and humidity level on the insulators’ surface. The electric field and potential difference were analyzed as well using the finite element method (FEM). The initiation of the arc was observed to appear at the area of insulators where the electric field was the highest. It was also observed that different coating distributions of pollution and humidity levels resulted in a change in the surface pollution layer resistance and an uneven distribution of the electric field. This indicates that the coated insulators’ parameters are directly related to the coating damage distribution on the insulator surface, particularly in the presence of humidity.

Pollution Flashover Characteristics of High-Voltage Outdoor Insulators: Analytical Study

Pollution Flashover Characteristics of High-Voltage Outdoor Insulators: Analytical Study

Effect of inverted T arrangement on AC pollution flashover characteristics of insulator strings

The arrangement of insulator strings has an effect on its pollution flashover characteristics. A new arrangement of insulator strings, inverted T-type arrangement, is proposed in this study. The electric field distribution is simulated and the pollution flashover characteristics are tested in an artificial climate chamber. The test results indicate that the inverted T-type arrangement can greatly improve the flashover voltage of polluted insulator strings, the ‘7 + 2’ inverted T-type arrangement can increase the flashover voltage of each insulator by 8.5% on average, and the ‘3 + 3’ inverted T-type arrangement can increase the flashover voltage of each insulator by 13.4%. The discharge process is different from that of the normal suspension string when the insulator string is inverted T-shaped, i.e. a local arc is produced at the low voltage end of the insulator string and develops downward along the suspension part. While as for the horizontal tension string parts, it is difficult to generate arc during discharge development.

Comparison of Surface Pollution Flashover Characteristics of RTV (Room Temperature Vulcanizing) Coated Insulators Under Different Coating Damage Modes

In recent years, room temperature vulcanizing (RTV) coated insulators have been increasingly applied in transmission lines. A large number of RTV coating damages on insulators are currently found. In this paper, three typical damage modes of the RTV coating were simulated, and then, the pollution flashover characteristics were studied. Results indicated that there is a big difference between the ac flashover performances of RTV coated insulators under different damage modes. The flashover voltage, as well as the critical leakage current, is largely influenced by salt deposit density (SDD), damage modes, and damage area. The relationship between SDD and U 50 still meets negative power function when RTV coating was damaged. Insulators with fan-shaped damage have lowest flashover voltage and greatest critical leakage current. Both 2D and 3D FEM models of the RTV coating damaged insulator pollution layer were developed to calculate leakage current density on the damaged surface; it is discovered that the starting position of the arc usually occurs where the current density is maximum. Different damage modes lead to the change of the surface pollution layer conductivity and the uneven distribution of the current density, which is the main reason that pollution flashover characteristics are directly related to the damage modes.

Influence of non‐uniform hydrophobicity distribution on pollution flashover characteristics of composite insulators

The authors investigated the effect of the insulator hydrophilic fraction on the pollution flashover performance by the up-and-down method. The hydrophobicity of parts subjected to a high electric field intensity such as two ends of an insulator, may be weakened by corona discharge. In this study, they simulated the behaviour of composite insulator surfaces at six hydrophilic fractions. Furthermore, arc discharge was recorded using a high-speed camera and the probability of arc discharge was analysed. They found that as the hydrophilic fraction was increased, the 50% probable flashover voltage first decreased and then increased. The wetting process and discharge type could be classified into two types and the flashover process could be divided into two stages by a clear hydrophilic fraction boundary through leakage current characteristic, discharge probability, and arc shape analysis. The results indicated that uneven hydrophobicity loss might lead to further flashover voltage reduction, up to 26.5% lower, than that with uniform hydrophilicity. This should be considered in transmission line design and maintenance of composite insulators.

Influence of tower anticorrosion coating as contaminant on operation characteristics of composite insulator

Anticorrosion coatings are commonly applied to prevent rust-based corrosion in transmission towers. Unfortunately, anticorrosion coatings may drip onto the surface of composite insulators during the construction process, which is likely to do harm to operation characteristics of composite insulators. This Letter was conducted to determine the influence of anticorrosion coatings on composite insulator performance. The mechanical properties, hydrophobicity, hydrophobic transfer, and flashover voltage of high-temperature vulcanised (HTV) silicone rubber specimens with and without the coating were investigated in detail. Appropriate solutions for avoiding unwanted effects on insulator performance are proposed accordingly. The influence of coating on the pollution flashover voltage of the composite insulator was also determined by changing the type, area, and shape of coating attached to the insulator surface. Finite element software was also used to analyse the effects of coatings on the electric field distribution of the composite insulator. The coating slightly affects the mechanical properties of HTV silicone rubber, but significantly impacts its hydrophobicity and hydrophobicity transfer. The pollution flashover characteristics of test composite insulators covered with the anticorrosion coating are also worst than those without coating.

The Influence of Main Components in PM2.5 on Composite Insulator Contamination Flashover Characteristics

This paper studies about the influence of main components in PM2.5 on insulator pollution flashover characteristics. A paper written by Institute of Atmospheric Physics Chinese Academy of Sciences presents the main components in Beijing’s PM2.5. Basing on that, an artificial pollution test in our lab. The test result shows that components in PM2.5 have no significant effect on insulator pollution flashover characteristics. But, in haze weather, insulators are easier to be polluted. As a result, the probability of insulator flashover become higher.

Study on AC Artificially Pollution Flashover Performance of EHV Class Insulator String of 32 Units

Study on pollution flashover characteristics of EHV system have great reference on engineering.In this paper,the relationship between 50% ac flashover voltage U50 of class insulator string of 32 units and ρESDD, ρNSDD was analyzed based on experimental results. It was shown that the relationship between U50 and ρESDD is the same as the one between U50 and ρNSDD, in which the U50 reduces with the increase of ρESDD by a power function, and the influences of ρESDD and ρNSDD on U50 are mutually independent. By using the least square method, the value of exponent of a and b were determined.

Effects of artificial polluting methods on AC flashover voltage of composite insulators

In artificial pollution tests, there are three polluting methods frequently used, including quantitative Brushing Method (BM), Dipping Method (DM) and Spraying Method (SM). Based on measurements of ac flashover performance of four types of silicone rubber composite insulators in the artificial climate chamber, this paper studied the differences on the flashover voltage of polluted composite insulators using these methods. The tests show that there are some differences on the pollution flashover characteristics, and the influences vary on flashover voltage of specimens using different polluting methods. Further, the differences are determined by the geometry of composite insulators as well as the polluting degree. However, the fitting formulas, which are simulated on ac pollution flashover voltages at the various pollution degrees for the same type of insulator, are consistent with three different methods. Moreover, the differences on exponents a characterizing the influence of Salt Deposit Density (SDD) on the flashover voltage are negligible for specimens whichever polluting method is used.