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Countermeasure and application of insulator flashover in transmission line

For a long time, restricting the normal operation of transmission lines is affected by air pollution and climate conditions, in such a situation, often trouble flashover of transmission line, and the transmission line failure, bring adverse effects to the normal operation of the transmission line. This article from the transmission line insulator flashover process of disturbance attack, analysis of transmission line insulator flashover factor disturbance attack, points on transmission line insulator flashover operation, proposed transmission line insulator pollution flashover countermeasure.
 
According to the survey, transmission line flashover of insulator flashover caused by disturbances in the power grid, the time of the attack incident probability ranking has risen to second, but due to loss of flashover is only about ten times to become the first lightning trouble lost. Whether the transmission line insulator overvoltage in the atmosphere, or over voltage, long-term operation voltage can be normal operation, but in the internal deposition of solid, or liquid in the transmission line insulator on the surface is dirt particles and gaseous, simple climate or weather conditions of fog, ice, snow and other attacks. Greatly reduced strength of electrical transmission line insulator, the flashover of transmission line attack may cause trouble, and even blackouts.
 
1 transmission line insulator flashover disturbance attack process
Transmission line insulator flashover attack is due to the contamination of insulator appearance, the appearance of polluted insulators will occur in bad weather or environment deliquescence, leakage current insulator appearance is the added, eventually caused by flashover, flashover in general conditions, with two needs conditioning, namely the insulator surface area sewage, insulators are in bad environment. Transmission line insulator flashover attack process first is divided into four stages, the first is the appearance of transmission line insulator contamination, namely the contamination particle deposition in the insulator appearance; second is the appearance of polluted insulators in the humid climate damp, dirty damp attack flashover have provided favorable conditions; moreover, the appearance of the insulator contamination is not uniform, there is no pollution site wet, dirt parts of boring, boring site needs to accept a higher voltage, when the voltage reaches a certain value and dry place, will attack the part arc; after all, when part of the arc at the critical point, the arc will run through two levels, caused by flashover.
 
2 The main factors of disturbance attack flash transmission line insulator
 
2.1 insulator flaws
Transmission line insulator in production, factors of production process will cause the internal structure of porcelain insulator is not symmetrical, in the long run, the mechanical function of insulators will follow the running time and adding gradually decreased. Under the long-term interaction of high voltage with mechanical fit, the breakdown voltage of insulator will decrease, which will cause insulator flashover. The other, in handling device or insulator, if not careful to make porcelain insulator appear crack, or the incomplete internal insulator porcelain insulator, the breakdown voltage will also be affected.
 
2.2 Effect of environmental factors
Transmission line in the use process, the insulator is generally exposed to atmospheric environment, a long time later, the particles in the atmospheric environment, the industrial waste gas, natural salt and birds shit will attached to the surface of the insulator, the insulator breakdown voltage drop. The temperature fluctuation in the natural environment will affect the breakdown voltage of insulator to a certain extent. In the climate, anti fog, wet or snow melt climate, will make the attached dirt attached to the insulator of the tidal water, then into the electrolyte water film layers, the leakage current of insulator add appearance probability situation occurs, resulting in the onset of flashover.
 
2.3 Effect of altitude
Atmospheric pressure and altitude is inversely proportional to the altitude increased, while the atmospheric pressure decreases, therefore, in the high altitude region, discharge more simple attack scene. As the discharge arc is relatively thick, after communication to zero, the transmission line will present the discharge scene, the arc is very simple re combustion, re combustion is difficult to quell.
 
2.4 Effect of creepage distance and shape structure
Transmission line insulator flashover and insulation creepage distance, insulation data and structure shape also have certain relations. In general, the pollution flashover voltage of insulators will follow the creepage distance increases, and the pollution flashover voltage of insulator flashover is higher, the lower the probability of scene attack; data will affect the insulation flashover, under the general condition, the breakdown voltage of glass is high, and the function of safe, cost-effective features, so the transmission line most of the materials made of glass insulators; insulators shape structure will also affect the flashover of insulators, because the shape is the thread shape, can increase the creepage distance, thereby increasing the flashover voltage of insulator, threaded with Naizang characteristics, not simple form of dirt.
 
3 transmission line insulator flashover method
 
3.1 transmission line insulator flashover operation points
 
According to the national standard grid, launched full salinity or grayscale test, then some units are lack of pollution flashover operation basically has: pollution measure lack of monitoring points is unreasonable, no reliable test data, test records gray less, lack of information etc.. With regard to these questions, the key point of insulator line flashover operation at the time of transmission line is to regulate the creepage, mainly concerning the existing external insulation equipment and the pollution level mismatch transmission equipment. Consider the main degree of power grids and equipment, to adjust the climb, especially in the past there is pollution flashover or adverse discharge in harsh climates of the region, the need to start climbing operations.
 
3.2 transmission line insulator pollution flashover countermeasure
 
(1) timing or timing of insulator cleaning.
In order to as far as possible to eliminate conditions flashover of transmission line attack, progress of insulator anti pollution ability, may not demand timing timing to insulator clean-up operation, cleaning can be useful to prevent the equipment insulation flashover presents the scene. It is necessary to carry out a cleaning operation every half year for insulators of transmission lines in comparison with the areas with simple attack pollution. It is worth noting that the insulator cleaning operation is just a gimmick to help eliminate the transmission line insulator flashover, insulator will present short power cut at each end of the clean-up operation after all, and will cause serious loss of power, therefore, after the cleaning technique of anti pollution flashover and cannot be used as a permanent solution, but also need to use anti pollution level of other techniques progress of insulators.
 
(2) increase the creepage distance.
, insulator creepage distance is long, its resistance to flashover is also higher, in the attack many times large-scale pollution flashover, can be adopted to adjust the creepage distance of the transmission line is improved, based on existing insulator string, and then add the 1-2 insulator, the practice can not only increase the insulator the appearance of the leakage distance, but also useful to control the leakage current, the progress of flashover voltage, but the adjustment of creepage distance is not allowed there lost [3]. Increase the creepage distance of main methods of adding the number of the insulator, increasing the diameter of disc rib may increase, the use of anti pollution insulator path, the other, in the operation of the equipment has been put into use porcelain appearance add silicone rubber creepage distance, can improve the transmission lines to prevent pollution flashover, flashover is a useful way.
 
(3) selecting suitable insulators.
Was used widely the primary insulator compared to ordinary type, bell type, double umbrella type and streamlined type, because the appearance structure of insulator will also impact on the pollution attack, so in the selection of the type of insulator need to select fit requirements of the insulator itself. Transmission line insulator shape structure and the surrounding air speed will directly affect the flow characteristics around the insulator, insulator appearance lubrication is not simple structure can reduce the eddy current, and insulator contamination, rough and simple form vortex, affecting the surrounding gas flow rate, the lower part of air pollution insulator. The double umbrella type antifouling insulator applied in China there are many types of insulators, the appearance of lubrication, a skirt is skew, eddy current is small, not simple dirt.
 
(4) spraying on the insulator flashover data.
After spraying flashover in transmission line insulator flashover, can solve the question in the general situation, anti pollution flashover coating has strong hydrophobicity and hydrophobicity transfer, when spraying convenient, can reduce and prevent the pollution layer moist, has anti pollution flashover effect was high, has been widely used in transmission line insulator flashover operation. Because of the high energy surface appearance is a porcelain insulator, a hydrophilic, when in a humid environment, the appearance of the electric porcelain water will form a conductive water film, and the insulator hydrophobic surface is sprayed materials, water will be set into big drops of water, water can not constitute a conductive film, and then increase the resistance of insulator the appearance of the. The constraint leakage current increases, eventually completed the antipollution flashover effect.
 
(5) using insulator monitoring skills.
Low value insulator and zero value insulator is directly influence factors of insulator flashover, with no shortage of insulator and insulator is lack of classification, both on the insulator string voltage distribution is not the same, can be based on this principle on spark gap method, acoustic pulse method and static voltage method, the monitoring of insulator. In accordance with the principle of current leakage due to insulator appearance will attack scene fever, can through the color coating method, infrared temperature measurement method for monitoring insulator. The other, after the appearance of the insulator infrared thermal imager temperature distribution into the picture, can be more intuitive in thermal insulators, and more convenient to detect faulty insulator.
 
In recent years, with Chinese science skills development innovation, on-line monitoring skills are developed gradually. On the one hand, an on-line monitoring system through the sensor and the insulator connected together at the top of the main insulator device maintenance unit, the main unit and sensor maintenance interface; on the other hand, after the solar battery box data acquisition device in the transmission tower on the line, the application of cohesion cohesion, at the moment, sensors to monitor the real-time data will be transfer to the corresponding data acquisition, data acquisition corresponding after the GPRS system or GSM system will transfer the data to the control terminal, the control terminal using the diagnostic instrument of insulator partial discharge intensity, leak current numerical judgment and analysis, and through the analysis of the results obtained with the insulator salt density, real-time contamination state feedback the insulator, to facilitate the timely processing of workers.
 
4 Epilogue
In transmission line insulator flashover disturbance attack is the most important element contains insulator flaws and environmental factor influence, the influence of altitude, creepage distance and structural shape etc., in operation on the pollution flashover of transmission line insulator flashover insulator, demand from the point of homework after leaving, or timing timing of insulator cleaning, increase the creepage distance, selecting the suitable insulator, spraying antifouling data in the insulator, the insulator inspection skills such as path, effective transmission line insulator flashover operation, prevent circuit fault flashover caused by sight.