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This study aims to predict the flashover voltage (FOV) of silicone rubber (SiR) insulators. Accordingly, it benefits from two methods, including an artificial neural network (ANN) model and a FOV gradient fitting model. The FOV and leakage current (LC) tests are carried out on one un‐aged and three aged specimens under uniform and longitudinal non‐uniform pollution circumstances. The proposed ANN model is designed based on equivalent salt deposit density (ESDD), pollution non‐uniformity degree, aging time, LC first harmonic magnitude I1, and total harmonic distortion. Furthermore, a FOV gradient model is proposed based on ESDD, I1, and creepage distance. To validate the proposed models, the FOV and LC tests are conducted on two different types of SiR insulators. Then, the predicted FOV from the ANN model and calculated FOV from the voltage gradient model are obtained. The results indicate that the relative errors of the ANN model and FOV gradient fitting model are <6.4 and 7.3%, respectively. [ABSTRACT FROM AUTHOR]

Currently, the equivalent salt deposit density (ESDD) is adopted to characterise the pollution degree and many environmental pollution parameters are used to characterise air pollution. However, the relationships between ESDD and environmental pollution parameters are not clear. For the purpose of studying the influence of environmental factors such as haze-fog, high-conductivity fog on the insulators contamination and the equivalence between artificial salt fog and natural highly conductive pollutions, a parameter named equivalent soluble salt concentration (ESSC) was proposed to measure the soluble salt amount of the atmospheric air in this study. Based on the measuring principle, an ESSC measurement platform was developed. The developed platform was tested in the laboratory and used to measure the ESSC in the field. According to the experimental results, it was found that the soluble components deposited on the specimen surface in the field are the same as that in the atmospheric air nearby. As the pollution deposition is an accumulative process, it is expected that combined with ESDD, the ESSC can be used to predict the ESDD, which would be of significance to study the accumulated mechanism of insulator contamination, as well as to the external insulation design. [ABSTRACT FROM AUTHOR]

The contaminants accumulated on the surface of transmission line insulator mainly come from the suspended particles in the air. Therefore, it is necessary to consider meteorological factors and environmental factors in the prediction of insulator contamination degree. In view of the advantages of generalised regression neural network (GRNN) in the aspects of fault tolerance and robustness, this study uses it to predict equivalent salt deposit density (ESDD). Furthermore, the adaptive mutation particle swarm optimisation and GRNN prediction model is proposed in this study. According to adaptive algorithm and mutation algorithm, the inertia weight and acceleration factor of particles are dynamically adjusted to achieve the purpose of searching global optimal smoothing factor. The optimisation method can effectively avoid the premature convergence of particle swarm optimisation (PSO) and solve the drawback that PSO is easy to fall into the local optimal value. The results show that the prediction model proposed in this study can effectively predict the insulators ESDD, and the prediction error is less than the GRNN and PSO–GRNN models. The research can provide guidance for the development of a more scientific and rational maintenance plan to achieve effective control of the contaminants of the line.

The pollution on insulators is composed of various chemical components, which threaten the stability of external insulation. However, the existing insulation designs have not taken this issue into consideration. This work aimed to study the influence of pollution chemical components on flashover performance of insulators with various materials. Flashover tests of porcelain, glass and silicone rubber insulators polluted by eight types of common contaminants were conducted. Based on the test data, the influence of chemical components and their solubility on equivalent salt deposit density (ESDD) and insulator flashover performance were analysed; and the electrical properties of different types of insulators were compared. Results show that the ESDD contribution rate changes with chemical components. The dissolution characteristic has a significant influence on the measurement of ESDD; slightly soluble contaminants need to be considered separately. The corresponding insulator flashover gradient for ions can be summarised as Cl^−

The composition of metallurgical contamination is rather special, which has a great influence on the contamination accumulation and flashover characteristics of the insulators. In this study, the 500 kV AC line insulators in metallurgical industry area of central China were sampled. The ion composition, element composition, micromorphology and particle size distribution of contamination at high and low end of insulator string were tested, respectively. The equivalent salt deposit density (ESDD) and non‐soluble deposit density (NSDD) of high‐voltage end, low‐voltage end and middle segment of three‐phase insulator strings were tested. The results indicate that the contamination particles are irregular in shape and dispersed with each other. The contamination particle size of high‐voltage end is larger than that of low‐voltage end. The main components of the contamination are Fe2O3 and CaSO4. The ESDD and NSDD of upper surface of upper phase is lower than that of middle phase and lower phase with the cleaning of rainwater. Due to the subsidence of metallurgical contamination from high altitude, the ESDD and NSDD of lower surface of the upper phase is higher than that of middle phase and lower phase. The ESDD and NSDD of lower surface of three phases reduce with the decrease of height. [ABSTRACT FROM AUTHOR]

In order to attain the pollution characteristics difference between composite rod insulators and standard disc-type suspended insulator which is critical to the insulation selection of transmission line, pollution accumulated on composite rod insulators and standard form suspended insulators suspended in the same tower near typical pollution sources in Zhejiang province were tested, including the equivalent salt deposit density (ESDD) and the non-soluble deposit density (NSDD). Also the factors caused the difference were analysed for the first time. It is shown that in Zhejiang area, the contamination on upper surface of composite insulators is more serious than that of standard form suspended insulators, and the situation is inverse on the lower surface; the entire shed value of ESDD and NSDD from composite insulator is 0.8, 1.27 times of the values from standard form suspended insulators, respectively. The contamination difference of upper surface and lower surface of the composite insulators is smaller than that of standard form suspended insulators. According to the analysis, the rainfall and PM10 concentration could notably effect the ESDD difference between composite insulators and standard form suspended insulators. With stronger rainfall and less PM10 concentration, the ESDD ration of composite insulators and standard form suspended insulators trend to be smaller. [ABSTRACT FROM AUTHOR]

The contaminants accumulated on the surface of transmission line insulator mainly come from the suspended particles in the air. Therefore, it is necessary to consider meteorological factors and environmental factors in the prediction of insulator contamination degree. In view of the advantages of generalised regression neural network (GRNN) in the aspects of fault tolerance and robustness, this study uses it to predict equivalent salt deposit density (ESDD). Furthermore, the adaptive mutation particle swarm optimisation and GRNN prediction model is proposed in this study. According to adaptive algorithm and mutation algorithm, the inertia weight and acceleration factor of particles are dynamically adjusted to achieve the purpose of searching global optimal smoothing factor. The optimisation method can effectively avoid the premature convergence of particle swarm optimisation (PSO) and solve the drawback that PSO is easy to fall into the local optimal value. The results show that the prediction model proposed in this study can effectively predict the insulators ESDD, and the prediction error is less than the GRNN and PSO–GRNN models. The research can provide guidance for the development of a more scientific and rational maintenance plan to achieve effective control of the contaminants of the line. [ABSTRACT FROM AUTHOR]

Pollution flashover performance of insulators is one of the key factors to be considered in the selection of external insulation for transmission lines at high-altitude areas. In pollution laboratories at Tibet high-altitude test base and Beijing ultra high voltage direct current (UHVDC) test base, artificial pollution tests of insulators adopted in AC 500 kV transmission project are performed both in sea-level region and real high-altitude regions, through which flashover voltages at typical equivalent salt deposit density are obtained. The relationship between altitude and flashover voltage is acquired as well. [ABSTRACT FROM AUTHOR]

Pollution flashover performance of insulators is one of the key factors to be considered in the selection of external insulation for transmission lines at high-altitude areas. In pollution laboratories at Tibet high-altitude test base and Beijing ultra high voltage direct current (UHVDC) test base, artificial pollution tests of insulators adopted in AC 500 kV transmission project are performed both in sea-level region and real high-altitude regions, through which flashover voltages at typical equivalent salt deposit density are obtained. The relationship between altitude and flashover voltage is acquired as well.

In order to attain the pollution characteristics difference between composite rod insulators and standard disc-type suspended insulator which is critical to the insulation selection of transmission line, pollution accumulated on composite rod insulators and standard form suspended insulators suspended in the same tower near typical pollution sources in Zhejiang province were tested, including the equivalent salt deposit density (ESDD) and the non-soluble deposit density (NSDD). Also the factors caused the difference were analysed for the first time. It is shown that in Zhejiang area, the contamination on upper surface of composite insulators is more serious than that of standard form suspended insulators, and the situation is inverse on the lower surface; the entire shed value of ESDD and NSDD from composite insulator is 0.8, 1.27 times of the values from standard form suspended insulators, respectively. The contamination difference of upper surface and lower surface of the composite insulators is smaller than that of standard form suspended insulators. According to the analysis, the rainfall and PM10 concentration could notably effect the ESDD difference between composite insulators and standard form suspended insulators. With stronger rainfall and less PM10 concentration, the ESDD ration of composite insulators and standard form suspended insulators trend to be smaller.

In recent years, the frequent occurrence of fog and haze in China has attracted increasing attention in the field of electrical insulation. Fog–haze weather is an extreme weather condition with high humidity, high concentrations of suspended particulate matter, and sometimes high conductivity. This exacerbates insulator surface contamination and moistens the contamination layer, which may lead to flashover incidents. Here, an experimental system was established to simulate the fog–haze environment under controlled and tunable conditions. Simulated contamination tests were then conducted using three typical insulators. The influence of insulator type and environmental parameters was investigated. Test results showed that higher humidity led to faster pollution accumulation for all three insulators. Moreover, equivalent salt deposit density (ESDD) on the surface increased linearly with increasing fog conductivity, and that on the upper surface rose faster. The ESDD increased significantly under AC voltage, especially on the lower surface. Finally, insulator contamination was studied in a real‐world fog–haze environment with periodic measurement of the ESDD and environmental parameters. The ESDD showed a good correlation with the PM2.5 and PM10 concentrations. This work should have relevance for the external insulation of the power grid to resist the effects of fog and haze. [ABSTRACT FROM AUTHOR]

EHV and UHV high voltage transmission lines frequently pass through high vegetation areas as well as national forests where there is a significant risk of wildfire by natural or manmade causes. Firefighters use aerial vehicles to douse fires by dumping large amount of fire retardant liquid that is conductive, thus increasing the risk of insulator flashover and power interruptions. In this paper, an ammonium polyphosphate based fire retardant liquid was evaluated to understand its effect on insulator flashover properties. Composite and ceramic insulators, suitable for 115 kV transmission lines, were studied by the solid layer test method. Tests were conducted with and without external wetting by fog. Results indicate that there is a high probability of flashover if the entire insulator is coated with the fire retardant liquid. Statistical methods were applied to extend the validity of testing results to predict flashover voltages at higher voltage levels of 230, 345 and 500 kV. It is shown that standard insulator dimensions used for EHV and UHV lines in fire prone areas could be deficient and additional insulation required to improve the flashover performance to acceptable levels in such locations has been determined. [ABSTRACT FROM PUBLISHER]

Under natural environment, the washing effect of rainfall has great influence on the cleaning of outdoor insulators. To study the law of natural contamination on the insulator surface in the rainy weather. The natural contamination experimental study has been carried out for four 500 kV transmission lines in hundreds of sites and stations in Hunan Province for five years. The equivalent salt deposit density (ESDD) and non‐soluble deposit density (NSDD) were measured monthly, and the meteorological data were statistically analysed. The results show that the residual ESDD and NSDD on the surface of insulators were affected by the rainfall intensity, duration and flushing angle. Meanwhile, based on the measured data of ESDD and NSDD, a cleaning model of insulators was established. The effects of splash on the bottom surface of insulators were studied by using the raindrop kinetic energy and Gaussian probability statistical distribution. [ABSTRACT FROM AUTHOR]

The surface pollution layer of polluted insulator absorbs fog water and gets damp in salt fog. Meanwhile, the salts in the salt fog deposit on insulator surface, which increases the surface conductivity and degrades the flashover performance of insulators. At present, the effects of fog water conductivity (γ20) and equivalent salt deposit density (ESDD) are analysed separately, which does not reveal the essence of the flashover in salt fog. In this study, a plenty of experiments on porcelain, glass and composite insulators are carried out in salt fog conditions, and the 50% flashover voltage stress, leakage current and variation of ESDD during the wetting process are studied. The concept of additional salt deposit density (ASDD) is proposed to quantitatively analyse the additional ESDD caused by salt fog. The test results indicate that the ac flashover voltage stress decreases with the increase of both ESDD and fog‐water conductivity. Both the ESDD and leakage current become larger in salt fog compared with those in clean fog. The ASDD can be applied to analyse the combined effect of ESDD and fog‐water conductivity and be expressed as ASDD = k × γ20 × ESDD. Then the flashover voltage stress is E = A × (ESDD + ASDD)−a. The values of k for the porcelain, glass and composite insulators are 0.179, 0.191 and 0.230, respectively. The flashover in salt fog environment is a special kind of pollution flashover in essence. [ABSTRACT FROM AUTHOR]

Till today, flashover because of pollution of insulators of overhead transmission lines (OHTL) is a major source of trouble in the electrical power transmission system. The importance of this problem can be assessed from fault statistics of high‐voltage transmission lines. In Egypt, for example, about 82% of the total faults of transmission and distribution OHTL are because of pollution. This study deals with laboratory tests, which have been carried out on polluted insulators of the OHTL that simulate desert environments. In this study, the effect of the variation of conductivity of the polluted layer by means of equivalent salt deposit density on flashover voltage (FOV) is investigated. The effect of variation of conductivity of the polluted, layer along the time required by the procedure needed to form dew, on FOV is also studied. This study is useful for indicating the worst period after the formation of dew, where the probability of flashover is increased. [ABSTRACT FROM AUTHOR]

The economy of transporting large amount of power over long distance makes high voltage transmission line an important component of the power system. Outdoor insulators provide electrical insulation as well as mechanical support between energized conductor and grounded parts of the tower. Its performance is closely related to the reliability of power delivery. Various parameters affect the insulator flashover performance, but the measurement and analysis of all those parameters would be a challenging and complex task during online inspection. The performance of the insulators is directly dependent on the electric field distribution inside and surrounding them. The aim of this work is to obtain the relationship between flashover voltage and electric field distribution. Accordingly, a novel electric field measurement technology, which was recently commercially available, was utilized in this paper to measure the electric field distribution around six different varieties of composite and ceramic insulators. The relationship between conductivity of the contamination layer and the environmental relative humidity was initially evaluated. Further, the patterns of the electric field distribution for clean, uniform and non-uniform contamination cases were studied and its relationship with the flashover voltages was explored. Electric field calculation with commercially available package was performed to validate the experimental results and extend the conclusion to higher voltage levels. [ABSTRACT FROM AUTHOR]

Pollution-induced flashover is critically affecting the safety operation of the power system so as to puts social production at risk. However, few literatures have predicted insulator pollution levels. Therefore, in this paper grey theory is introduced and GM (1, N) method for the prediction of pollution on insulator surface was proposed. Further, a pollution test lasting for 9 months was conducted to build the GM (1, N) model. The test of another 4 months was also conducted to contrast the test results (ΔESDD (Equivalent salt deposit density)) and predicted results. The research results have shown that: GM (1, N) was applicable to predict the pollution on insulators at the cases of poor information with less data for building model. Besides, considering more environmental factors is conducive to improving the prediction accuracy of the GM (1, N) model. However, wind speed that varied very little during the 13 months' nature contamination periods in Chongqing can be neglected, which may improve the accuracy of the model (with its relative error decreasing from 7.9% to 6.3%). Next, the application scenario of the model is proposed. In addition, GM (1, N) method has potential applications in other field, and the prediction accuracy of GM (1, N) model can also be improved by increasing or decreasing the number of influencing variables as well as the number of samples. The proposed GM (1, N) method provides guidance for anti-pollution work in power systems, which promotes the reduction of flashover accidents and maintain social production safety. • GM (1, N) method for insulator pollution prediction was proposed. • 13 months' pollution tests were conducted for building and validation of models. • The application scenario of this model was presented. • Test results can provide guidance for anti-pollution work in power systems. • GM (1, N) models could be also used as prediction model in other field. [ABSTRACT FROM AUTHOR]

In designing EHV transmission systems, specific knowledge about the creepage distance of the insulator, which is subjected to adverse environmental contamination, is important. Various system components' configurations can be properly coordinated through the appropriate application of the relationship between insulator creepage distance, the equivalent salt deposit density (ESDD), and the insulator diameter. In this paper, a general relationship between the creepage distance, ESDD, and diameter of the insulator has been proposed using the dimensional analysis technique [ABSTRACT FROM PUBLISHER]