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In recent years, vibration signals have been applied in mechanical device fault diagnosis, however, vibration signals are submerged by a large number of background noises in practice, which reduces the fault diagnosis accuracy. In this paper, we present a combination unit of self-adaptive slope and soft thresholding in the Deep Residual Shrinkage Networks (DRSNs), the new unit enables the DRSNs effectively learn the useful information out of the threshold region rather than completely reserving them. Furthermore, we use the attention mechanism to automatically infer the adaptive slope. Many experimental results demonstrate that the improved DRSNs can obtain more superior performances compared with the original DRSNs under background noise.

Hot water is a kind of deicing medium with wide sources, and the impact force of its ejection is easy to control to avoid damaging the surface of glass insulator. In order to reveal the influencing factors of hot water deicing and their effect on the deicing time of glass insulator, an experiment was conducted where LXY-120 glass insulator was selected to measure the hot water deicing time under different circumstances. The results show that initial water temperature has significant effect on deicing time. At certain range, deicing time can be greatly reduced as initial water temperature increases, and it also affects deicing time increasement caused by heavier ice weight. Ejection distance and outlet pressure both have near linear relation with deicing time. It concluded that when conducting hot water deicing, on the premise of ensuring safety distance, shortening deicing distance, optimizing outlet pressure and initial water temperature can improve the ice melting efficiency.

In order to grasp the corrosion failure characteristics of silicone rubber in an acidic environment, an artificial mist box was used to artificially simulate the corrosion conditions acting on the silicone rubber, and the changes in its surface characteristics were analyzed. The research results show that under the combined action of acid mist and electric field, the physical and chemical properties of composite insulators have declined. There are holes and cracks on the surface, and the hardness increases with the corrosion time. Before flashover, if there is no obvious discharge in the withstand voltage process, the contact angle, relative dielectric constant and absorption peak area change little with the increase of corrosion time. The analysis shows that the damage rate of large-area corrosion of silicone rubber is very slow. Acidic substances will cause the main chain and side chains of the silicone rubber to break, and the aluminum hydroxide in the silicone rubber also reacts with strong acids, resulting in the destruction of the structure of the silicone rubber. The physical and chemical properties are reduced.

Lightning could lead to insulation failure if there is no protective steps were taken. Typically for this reason a lightning arrester is used. A novel insulator incorporating an arrester and an insulator for 10 kV power lines was designed to integrate the insulator with the lightning arrester as a single entities. This paper aims to study the AC flashover performance and insulation coordination of novel lightning protection composite insulator. The results shows that $U_{f}$ decreases with the increase of ESDD. Specifically, when ESDD increases from 0.01 mg/cm2 to 0.2 mg/cm2, $U_{f}$ decreases from 44.4 kV to 15.1 kV. Thus, the maximum air gap distance to ensure the normal operation of the insulation section is 19 mm, 13mm and 10mm, when ESDD is 0.07mg/cm2, 0.09mg/cm2, 0.11mg/cm2 respectively. This paper presented the insulation coordination of the insulation section, ensuring that the protection gap can work normally.

Based on loading principle, this paper presents an optimal design method of the device which can improve the anti-icing and anti-galloping ability of transmission lines. Firstly, a lumped parameter system model is adopted, with the total mass of the device, the maximum available arm length and the initial freezing angle as the design variables, and the line-device mass equation as the constraint conditions for the first optimization. Using modal analysis method, the distribution coefficient of the device was taken as the design variable, and the anti-galloping effect of the line-device system was taken as the objective function for the quadratic optimization. Applying the optimized model to actual engineering, the calculation results show that the anti-galloping ability of the line can be improved by nearly 50%.

This paper presents a passive and noninterventional combined anti-icing method, which is composed of an anti-torsion and anti-galloping device and anti-icing coatings. First, the mechanism of anti-icing and anti-galloping of the device is analyzed from two perspectives: the guiding effect of the icing process and the separation frequency effect, and then a laboratory method for testing the adhesion of the coatings is given, and a corresponding deicing model is established for the comprehensive effect of both. Applying the deicing model to actual project, and the results show that under the action of the proposed method, the icing process tends to proceed on the windward side, and the ice coating adhesion force is small. Under appropriate environmental conditions, when the actual ice layer thickness reaches the critical ice thickness, the natural ice falling off can be realized.

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 U50 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.

Road traffic safety is related to many factors, and it is also an important index to test the level of traffic safety management and the utilization rate of traffic investment. The investment in transportation industry, mainly composed of road traffic environment and traffic management investment, plays a decisive role in road traffic environment and is the main reason bring up traffic safety accidents. The medical investment in traffic safety assistance system includes pre-hospital emergency treatment and post-hospital treatment, and it's amplitude reflects the emergent management level of traffic safety. In order to explore the impact of China's road traffic safety management level and traffic investment utilization rate on road safety, this paper selects relevant indicators of the transportation industry investment and the medical industry investment in 31 provinces of China from 2004 to 2018 to construct a fixed effect model for studying the impact of various factors on the direct property loss in road traffic accidents. Results show that: 2004–2018 GDP, the number of newly registered civil vehicles, the number of medical and health institutions and the urban per capita road area have a positive correlation with the direct property loss in traffic accidents; the investment in transportation and the total high length have a negative correlation with the direct property loss in traffic accidents.

Recently, a novel lightning protection composite insulator, combining an arrester and an insulator was developed for 10-kV distribution lines. This paper aims to study the AC flashover performance of the novel composite insulator. Firstly, the structure of the insulator was introduced. It is divided into two parts: the insulation section and the arrester section. Then, AC flashover tests of different icing thickness were conducted at Natural Icing Test Base. Further, the empirically derived equation for calculation of AC flashover voltage was obtained. The findings indicate that low, medium, and heavy pollutions cuased different types of arcings. This can be used for desiging insulators for various pollution levels.

Insulator contamination directly threatens the safe and stable operation of the overhead line. Through spatial electric field monitoring, it is expected to realize insulator pollution condition monitoring and contamination flashover warning in a non-contact way. So in this paper, the spatial electric field distribution characteristics of 110 kV composite insulators are simulated, where the effects of different surface states and their discharge levels on the spatial electric field of insulators are analyzed. On this basis, a non-contact monitoring method for composite insulator pollution based on the spatial electric field is proposed. The results show that there are significant differences in the spatial electric field of the composite insulator among three conditions of clean, pollution layer wetting, and dry band arcing. With the increase of pollution layer wetting and dry band arcing, it would lead to an increase of the amplitude of the spatial electric field of the insulator. It is feasible to identify the degree of pollution layer wetting as well as dry band arcing of the insulator string, by fixed-point monitoring the spatial electric field signal at the cross-strand of d = 0.5 m and directly opposite the last three positions. Research results can provide references for the online monitoring of overhead line pollution insulators and its flashover warning.

Heavy icing on insulators may cause flashover, making great threaten to the operation safety of power system. It is of significance to research the icing process of insulators for the external insulation selection. Current research about icing process lacks experiments in complete natural condition. To study the icing accretion characteristics of insulator and the shape of natural ice, the natural icing tests of porcelain and glass insulators were conducted in Chongqing University Xuefeng Mountain natural icing station in this paper. In addition, the environment parameters such as temperature and wind velocity were recorded through the experiments and the influences of these factors on insulator icing were analyzed. Results indicate that, under natural environment, icing shape of porcelain and glass insulator are similar, and there is a distinct difference of ice between windward and leeward side on insulator surface. Relationship between insulator ice mass and icing time is nonlinear. Insulators natural icing process can be obviously divided into earlier term, medium term and late term. Icing degree of insulator is related to wind speed, the environment temperature and the shed diameter. The simulation results demonstrate the distribution of airflow and water droplets around the insulator, and can explain the different icing degree beween windward side and leeward side, consistent with natural test. Results and analysis in this paper could be practical reference to the external insulation design.

In order to study the pollution characteristics of suspension composite insulators, the wind tunnel experiments of typical big-small sheds composite insulator were carried out with different wind speed under voltages of different polarities and levels. The results showed that the NSDD (non-soluble deposit density) of composite insulator increases with the increase of wind speed, contamination degree of leeward side of insulator is greater than that of windward side, contamination degree of top surface is greater than that of the bottom surface, and NSDD of small shed surface is slightly larger than that of big shed surface. Thus, positive and negative polarities of DC voltage have similar effect on increase of contamination on insulator surface while AC voltage has almost no effect on the contamination degree. In the DC energized condition, the contamination distribution along the string is also non-uniform. In order to explain uneven distribution phenomenon along the string, the multi-physics coupling software COMSOL is used to calculate the electric field around the insulator. Furthermore, basing on field charging theory, the value of electric field force on particles around insulator surface was calculated and the mechanism of uneven contamination distribution on insulator sting was then explained. The research method and results can provide not only reference to establishing natural contaminating model but also significant meaning for the external insulation design and selection.

The external insulation contamination on real transmission line is mainly composed by the mixture of NaCl, CaSO4 and other various kinds of constituents. Different constituents have effects on the flashover performance of various types insulator, but it is still not considered by the existing standard about external insulation design in polluted region. This paper investigated the electrical property of different types of insulator string under typical pollution constituents. During the tests, the insulator samples were polluted by NaCl, CaSO4 and mixture pollution constituents in representative region respectively. The flashover data was obtained and then the waste rate of insulation were calculated based on pollution withstand voltage method. Research results indicate that, The characteristic b of ceramic, glass and composite insulator under mixture constituents pollution is obviously lower than that under NaCl, traditional design method overrates the influence of ESDD on flashover performance; the electrical property of applied insulator under mixture pollution constituents should be studied to provide better reference for the external insulation design; When using the pollution withstand method to design the external insulation, the leakage distance of insulation should be chosen basing on the mixture pollution constituents in practical region.

Pollution materials affect insulator flashover performance, and there is long-term significance in researching it. In this paper, common kinds of nitrates were used as the soluble pollution, and the ac flashover tests of typical glass insulator were carried out. During the tests, the samples were polluted by dipping method. Also, up-and-down method was used to obtain the insulator flashover gradients under different pollutants and ESDD values. Basing on the test data, the effects of nitrates on insulator flashover performance were analyzed. Research results indicate that, using the current method to calculate the flashover gradient of insulator polluted with nitrates, the relative error will reach 24%; Flashover gradient of insulator under nitrates is higher than that under NaCl; KNO3 corresponds to lower flashover gradient while Ca(NO3)2 corresponds to a higher one; The pollution characteristic b of glass insulator under nitrates is within 0.18 – 0.25; The flashover gradient EL of glass insulator polluted by single or mixed nitrate can be expressed by 25.6×ESDD−0.21.

The motion mechanism of the supercooled droplets on insulator surfaces with superhydrophobic coating will affect the amount and distribution of droplets, which further affects the icing on surfaces. In this paper, the tests were carried out to explore the motion process of the droplets before frozen on superhydrophobic surfaces under the condition of continuously spray supercooled droplets in artificial climate chamber. The motion properties of water droplets on superhydrohobic surfaces and its influencing factors such as Contact Angle (CA), Contact Angle Hysteresis (CAH) and roughness were investigated. Besides, the artificial icing tests for glass insulators with different superhydrophobic or hydrophobic coatings were carried out and the influences of motion properties on icing of insulators were analyzed. The results show that the larger CA and roughness are and the smaller CAH is, the easier it is for droplets to roll off and the better motion property is, causing the longer icing delay time of insulators.

By comparing the differences of electric field distribution and 50% flashover voltage between common arrangement insulator string and adding booster shed every four insulators (ABSEFI) arrangement insulator string during the melting period, this study explores the influence of booster sheds on ice-covered 750kV class tension insulator strings. Computer simulations and artificial icing flashover tests were used for the comparative analysis. Numerical simulations were done by the use of the finite element method (FEM). The simulation results show that the electric field strength at insulator steel-feet, which booster sheds have little impact on, is much higher than that in other places. Therefore, compared with common arrangement, there is no obvious improvement in the potential distribution after booster sheds being added on the tension string. Artificial icing flashover tests were carried out to compare the 50% icing flashover voltage of these two arrangements in different pollution severities. In addition, the flashover process of these tests was analyzed to study the influence of booster sheds to icing flashover. The experimental results show that, under the condition of 10 mm thick icing, the booster sheds increase the icing-flashover voltage of tension insulator strings by about 7%. The improvement is irrelevant to pollution severities.

Under drizzle, light rain, heavy fog and other adverse weather conditions, polluted insulators may flashover under an operating voltage which serious threat to reliable operation of power systems. Therefore, it is very important to understand the natural pollution accumulating rule of insulator energized in the operating voltage. This paper takes the XP-70 insulator string being suspended without voltage in a certain power network in Shantou as the sample, tests and analyzes the pollution depositing rules of it. Test results indicate that: The performance of natural pollution deposit is related to geographic location and voltage class. The accumulation rate of non-soluble salt deposit density (NSDD) on the surface of insulator is more serious than that of equivalent salt deposit density (ESDD). The pollution depositing situation of insulator is different under different voltage classes, the pollution accumulating situation of the 110kV line is the most severe, while that of the 220kV line is a bit lighter and the 500 kV line is the lightest. The pollution levels of transmission lines in Shantou area are mainly c and d. The test results can be used to draw the map of pollution areas, help workers to clean insulators and direct external insulation coordination and design in the pollution area.

Current transformer, the major primary equipment in power system, can transform a large primary current into the standard 5A or 1A current. It provides current for the measure device and the coil of relay protection, meanwhile makes the primary equipments isolate from the secondary equipments. With the development of grid, SF 6 current transformers have been widely used. Once the fault of the internal insulation support in SF 6 current transformer appears, it will threat the safe operation of power systems. In recent years, the fault accidents of current transformer have occurred form time to time. This paper introduces the fault conditions of 500kv current transformer in the area under the jurisdiction of Xiamen EHV Power Transmission and Transformation Bureau. After it be sent back to factory and disassembled, we found that many large area of paint have come off the inner surface of shell of the current transformer, and that there many blister on the inner surface of shell. Meanwhile, send the same batch transformers back to the factory and disassemble, we found that there are many problems in the production process. So this paper suggests that the production process of SF 6 current transformer should be monitored. And after it has been installed, we have to do the aging test and voltage withstand test. To prevent the same fault of 500kv current transformer occurs again, the results in this paper can give some reference and engineering application consult.

It is important to study the natural characteristic of pollution accumulation and flashover performance of insulator energized the operating voltage. This paper mainly focus on the insulator strings operating in a 500kV power network in Chongqing, tests and analyzes the pollution depositing rules and flashover performance of them. Test results indicate that: the value of equivalent salt deposit density (ESDD) on the top surface of insulator is lower than that on the bottom, as well as the value of non-soluble deposit density (NSDD);the accumulation rate of NSDD is heavier than that of ESDD; electric field distribution and precipitation exert a strong influence on the insulator obviously; at the same pollution level, the flashover voltage of natural contaminated insulator is 2 times as high as that of artificial polluted insulator, which mainly caused by the difference of pollution materials and non-uniform pollution distribution on the insulator surface. The results of this paper may be the reference for external insulation coordination and design in the pollution area.

This paper takes the composite insulator being operated in a certain 110kV power network in China as the sample, tests and analyzes the pollution depositing rules and flashover performance of it. Test results indicate that the equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) on the upper and lower surface of composite insulators energized running voltage is different. The ratio of the ESDD and NSDD of upper surface to that of lower surface is 0.76 and 0.46 separately. The structure and shape of polymeric insulators have influence on the pollution deposit levels and non-uniform degree. The dispersion of the pollution flashover voltage of naturally polluted composite insulators is great. Under the same condition, the pollution flashover voltage of naturally polluted composite insulators is higher about 50% than that of artificially polluted composite insulators. The difference of hydrophobicity, component of contamination and non-uniform degree of pollution are the main reason that caused the pollution flashover voltage of naturally polluted composite insulators is higher than that of artificially polluted composite insulators.

In this paper, the DC flashover characteristics of iced insulator strings were explored in the multi-functional artificial climate chamber through four methods, namely, the average flashover voltage method, the minimum flashover voltage method, the maximum withstand method and the 50% withstand method, with the typical DC porcelain insulator strings and composite insulators. The results indicated that the average flashover voltage and the minimum flashover voltage obtained respectively by the average flashover voltage method and the minimum flashover voltage method were in normal distribution; the 50% flashover voltages gained by the two test methods mentioned above were about 8.0%~9.8% and 3.8%~5.9% higher than that gained by the 50% withstand method respectively, which justified the feasibility of employing the U-curve method and the average flashover voltage method to study the flashover characteristics of iced insulators and their affecting factors.

The electric performance of polluted insulator string may reduce under high altitude. The paper studies the AC pollution flashover performance of insulators at different height of altitude field and chamber climate separately. The test results show that: The deviation between test results with the artificial and field experiments is less than 8%, when the test carried out in climate chamber under low air pressure conditions, the characteristic exponent n describing the influence degree of air pressure on pollution flashover voltage which has influence on the pollution flashover voltage of insulators is mutative, and the value of n is related to the pollution, insulator type etc.. Under AC voltage, n is 0.50~0.60. The composite insulator is superior in external insulation selection in high altitude and heavy polluted areas. The results obtained by the test which carried out in climate chamber can guide the designing of the external insulation.

Non-uniform distribution on an insulator has a great influence on the DC pollution flashover voltage. a lot of investigations have been carried out on the non-uniform pollution flashover performance of the porcelain and glass insulators, but the research on the composite insulators is still very few. In this paper, based on the artificial pollution tests carried on the DC composite insulator, the influence of non-uniform pollution distribution of the DC composite insulator on the flashover performance is analyzed, and the correction formula of the non-uniform pollution flashover voltage is proposed. The test results show that, the correction formula indicating the influence of non-uniform pollution distribution on the flashover voltage could be expressed as K=1-b×log(T/B). For the tested composite insulator, the factor b is 0.141~0.156, which is smaller than those of porcelain and glass insulators.

Switching impulse discharge performance of air gaps at high altitudes, which is fundamental in the extra-high voltage external insulation design, remains the unsolved key technology across the world. Due to the limited applicable range of g parameter method, which is recommended by IEC Publication 60-1(1989), this paper aims to explore the relationship between positive switching impulse 50% discharge voltage U 50 of rod-plane air gaps and atmospheric parameters, and proposes two new voltage correction methods based on parameter g and atmospheric pressure ratio respectively, which are 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 positive switching impulse 50% discharge voltage U 50 of rod-plane air gaps is a power function of relative pressure and relative air density, taking the influence of absolute humidity into account; g parameter method in IEC Publication 60-1(1989) does not adapt to the regions with an altitude above 2000 m and under the h/delta>15 g/m3 condition; in comparison with the correction method based on g parameter, the one based on relative atmospheric pressure has a wider applicable range and less errors; U 50 varies within 1.0%-1.15% range with per g/m increase of absolute humidity.

In This work, laboratory investigations were carried out on 110 kV composite insulators, 7 units of an IEC standard suspension porcelain insulator string, and 7 units of a XWP-160 antipollution porcelain insulator string with 64 kV voltages in the multifunction artificial climate chamber of Chongqing University. Based on the test results, it puts forward that there are evident differences in ice accretion speed, ice density and ice structure between energized insulators and nonenergized insulators. The electrical field stress has an important influence on ice type and ice structure accrued on the insulators. Both flashover voltage and withstand voltage of the insulators covered with ice at an energized condition are higher than that at a nonenergized condition. Finally, it analyzes the factors that influence the ice type, structure and the flashover performance of an iced insulator.