The non-linear relationship between the pollution flash voltage and atmospheric pressure P can be expressed as U=U0 (P/ang) (It is the pollution flash voltage at normal atmospheric pressure 0; it is the characteristic index of atmospheric pressure effect. At atmospheric pressure and atmospheric pressure 68kPa Next, AC fouling tests were conducted on standard suspension insulator strings and stain-resistant suspension insulator strings to obtain the former r/value of 0.50 and the latter, z value of 0.60, based on the scene at altitudes of 0.8 km and 3.2 km. For AC flashover test results of suspension insulators, post insulators and bushings, it is proposed that the insulator flashover voltage of insulators decreases with increasing altitude by 7% to 9%/km.
Whether the results of artificial simulation test results and natural environment test results are equivalent and whether artificial simulation test results can directly guide engineering applications are issues that external insulation design and the majority of researchers are very concerned about. However, so far, systematic pollution tests at high altitude sites at home and abroad and the comparison of high altitude scenes with artificial climate chambers have rarely been reported. Therefore, this article simulates the natural environment in the artificial climate room and the Golmud (elevation 2820m, atmospheric pressure (72.0+1.0)kPa), Najitai station (elevation 3575m, pressure (66.0+1.0)kPa) along the Qinghai-Tibet railway, Wang Kun Station (4448m above sea level, atmospheric pressure (58.5+1.0)ld'a) was used to conduct field comparison verification tests at three elevation points. The results of this study will provide reference for the selection and design of external insulation for transmission lines in high altitude areas.
The insulator of the test sample to be tested is washed and hung on the sample rack to air dry naturally, and the hydrophobicity of the surface material of the composite insulator is pretreated before the contamination, so that a very thin hydrophilic substance is attached to the surface of the insulator. Contamination of the test sample. Using the recommended solid-layer soaking method in the protocol, the sewage liquid was a mixture of sodium chloride, water, diatomaceous earth, and silica (the ratio of diatom to SaN oxide was 10:11. Insulators were used. Direct flashover test after soaking (wet soil method), that is, the insulator after soaking is not dripping along the skirt of the umbrella and wipe off the dirt on the steel foot and the steel cap, and then hangs on the test product frame, and then After the voltage lead is stable, the flashover test shall be carried out using the uniform voltage boost method, and the ambient temperature and air pressure at the flashover shall be recorded at the same time. After the flashover, the water sprayer shall be used to gently spray water onto the surface of the insulator so as to be dried by the arc. The surface is wetted again.The test adopts the uniform pressure rising method, and each string of insulators conducts 4 to 5 flashover tests; in the same degree of contamination, 3 to 4 strings of insulators are selected for repeated tests, and the average error between them is no more than 10%. The average value of all flashover voltages is the flashover voltage of the string of insulators at the degree of contamination.
In order to compare the difference between the artificial climate chamber simulation test results and the high altitude field test, this article uses the same test method as the on-site test in the artificial climate chamber. When artificial climate chamber simulates high altitude, the temperature of artificial climate incubator also changes. At a laboratory elevation (232m), the temperature is 30°C. However, when the vacuum is used to pump air to lower the pressure in the climate chamber to 71.7, 65.1, and 57.8 kPa, the temperature in the climate chamber will drop to about 26, 24, and 22°C. In other words, when the pressure changes by 10 kPa, the ambient temperature of the climate chamber will decrease by 2.0-3.0°C.
The relationship between the insulator flash voltage and the salt density and pressure obtained by artificially simulating the high altitude depression is basically the same as that obtained from the high altitude field test: that is, as the altitude increases, the degree of contamination increases and the average number of insulator strings decreases; There are certain differences between insulator values ​​and field test results under simulated artificial climate incubators. Taking three XP.70 insulators as an example, when the salt density is 0.03 mg/cm and the air pressures are 71.7, 65.1 and 57.8 kPa, respectively, the field tests are 29.8, 28.5 and 26.7 kV. The simulated test flash voltage is 29.5 respectively. , 28.8 and 26.5kv.
The insulator flash voltage obtained under different test methods has certain differences. The insulator flash voltage value obtained by the steam fog method is approximately 4% to 10% higher than the flash voltage obtained by the wet method, but obtained from the two test methods. Pollution flash voltage with the law of pressure changes are basically the same. In the field test, the temperature difference of different test points is quite different. To make the test results comparable, it is recommended to perform temperature correction on the insulator flash voltage. The error between the artificially simulated high-altitude test results and the high-altitude field test results is within 8%, and the relationship between the AC voltage and the salt-tightness and air pressure of the insulators obtained by artificially simulating the low-altitude atmospheric pressure and the high-altitude field test results The laws are basically the same. Insulator pollution voltage impact pressure characteristics of the index and the insulator type, salt density and so on, AC value is about 0.4 ~ 0.6.
[Advantages of α-linolenic acid compared to DHA]
DHA (brain gold) is one of the derivatives of α-linolenic acid. Supplementing α-linolenic acid has advantages over directly supplementing DHA:
Different medical importance: α-linolenic acid is an important nutrient in the 21st century. It is an unsaturated fatty acid necessary for the body. The human body cannot directly synthesize it by itself and must be ingested from the outside world. DHA is not. The human body's own regulation is different: α-linolenic acid is the precursor of DHA, which can provide DHA to the maximum extent according to the human body's needs. However, direct supplementation of DHA is a strong supplement that the human body cannot control itself and is prone to negative effects. Applicable to different groups of people: α-linolenic acid is helpful in regulating blood pressure, blood lipids, and blood sugar, while DHA comes from fish oil. Pregnancy-induced hypertension inevitably contains animal cholesterol, and women with gestational hypertension, obesity, and overweight cannot use it. use. The "Usage" of the secondary directory is modified to:
Direct drinking: average daily dose of 5-10 ml; drop on warm rice, bread or steamed buns, reduce to 1-5 ml for children.
Smart salad dressing: Add to cold dishes or salads.
Soup seasoning: drop into cooked porridge, soup, and milk.
Baked pastries: Use organic nutritious oils instead of hydrogenated oils or butter in baked pastries.
Homemade preparation: mix it with ordinary edible oils such as soybean oil, peanut oil or rapeseed oil in a ratio of 1:5-1:10 before consumption.
Secret combination: Take 5-10 ml of nutritious oil and mix it with sugar-free homemade yogurt or sugar-free yogurt before eating. It is a popular anti-cancer food therapy in Europe and the United States.
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