China's tea culture has a long history, and tea is one of China's major symbols. China is the origin of tea trees. Tea trees first appeared in the Yunnan-Guizhou plateau and Xishuangbanna area in the southwest of China. According to inspections, the word “Tea†first appeared in the “Hundred Masters Monument†and “Wui Fai Monumentâ€, and it was about the middle of the Tang Dynasty, from about 806 AD to around 820 AD; later, the Tea Sutra was also adopted. The word "tea". Prior to this, "tea" was represented by "è¼". There are hundreds of modern Chinese teas. According to its historical analysis, there are three kinds of situations: the restoration of historical teas and traditional teas, most of which belong to newly established teas.
Xiao Bian remembers that when he was young, the men in his hometown liked to hold cups and have a cup of tea in hand, which made him feel very comfortable. The demand for tea in our country is very large, because it is well-known that drinking tea has many benefits, so the place for growing tea is also increasing.
The techniques used to produce tea include picking, drying, spreading, seeing green, shaking green, killing green, kneading, and baking. In the process of fixing (greening) the purpose is to use high temperatures, quickly destroy the activity of the enzyme, and consolidate the already formed quality. How is the temperature specific?
The killing process first requires the rapid and timely destruction of the enzyme's catalysis. Temperature is one of the most important factors affecting the catalytic action of enzymes. Within a certain temperature range, the temperature rises, which not only speeds up the catalytic reaction of the enzyme, but also accelerates the destruction of the enzyme. The optimum temperature for so-called enzymatic action is that at this temperature (under certain conditions) the maximum amount of enzymatic reactant is reached.
At the optimum temperature, the rate of catalysis of the enzyme doubles for every 10°C increase in temperature. The optimum temperature of general plant enzymes is 50-60°C. Some data suggest that the optimum temperature of polyphenol oxidase in tea leaves is 52°C.
As the temperature rises, the enzyme also deteriorates due to thermal effects. When the temperature exceeds the optimal temperature of the enzyme, the enzyme activation is lost. The former is larger than the latter due to an increase in activation caused by an increase in temperature, resulting in a decrease in the speed of the enzymatic reaction. The higher the temperature, the greater the drop. When the temperature rises to a certain limit, the enzyme is completely destroyed and the enzymatic reaction rate is zero. This temperature limit is called the critical temperature of enzyme passivation.
In the process of fixing, high temperature must be used to quickly increase the temperature of the fixing leaves in an extremely short period of time, and quickly pass the optimum temperature of the enzyme to reach the critical temperature of enzyme passivation. The enzyme is completely destroyed by heat and it is difficult to determine how high the temperature is. Because of the other factors. In the process of fixing, the critical temperature of passivation of polyphenol oxidase was determined. According to the data measured by Anhui Agricultural College, it was initially assumed to be 85°C. The critical temperature of enzyme passivation in tea needs to be further studied. However, according to some test results, the fixing process requires that the temperature of the leaf quickly rises above 85°C.
The time required for the leaf temperature to rise from room temperature above 85°C is one of the most important factors in the fixation technique. From the above, it can be seen that the enzymatic reaction is quite dramatic before the temperature of the leaf rises above the critical temperature for the passivation of the enzyme. If the period of warming up is prolonged and the amount of change is relatively increased, chemical changes in the contents of the leaf may be transferred to the “deteriorated†route, resulting in the generation of red stems and red leaves. The general fixation technology requires that leaf temperature rises above 85°C within a period of two minutes, and the maximum time should not exceed three or four minutes. Otherwise, red stems and red leaves may appear. Leaf temperature above 85°C will continue for a certain period of time. After the complete destruction of the enzymes, the temperature of the leaves should be reduced. Especially when the water content of the leaf is reduced to nearly 60%, the leaf temperature is too high, and the individual shoots and tips of the high tenderness will be coked.
Tea not only requires temperature during production, but also has strict requirements on temperature during storage. Tea moisture absorption and strong odor absorption, it is easy to absorb moisture and odor in the air, if the storage method is a little improper, it will lose flavor in a short period of time, and the more the Qing Dynasty fermentation of high-quality aromatic tea, the more difficult to save. Usually after the tea is stored for a period of time, the aroma, taste and color will change, the original new tea will disappear, and the taste of the tea will be gradually exposed. Temperature: Storage of tea leaves at higher temperatures will accelerate the aging of new teas and change the quality of tea. Generally, the temperature of the tea leaves is increased by 3 to 5 times for every 10°C increase in temperature. If tea leaves can be stored below 0°C, aging can be almost completely prevented. The temperature recorder can come in handy at this time, LCD can display the recorded temperature, grasp the temperature, and store the tea.
I. High & Low voltage cabinets installation of power plant
1. 10KV high voltage switch cabinet installation of power plant
2. 0.4KV low voltage switch cabinet installation of power plant
3. Installation of generator protection system, synchronization system, transformer protection, H.V. motor protection, circuit protection in a power plant.
II. Electrical configuration testing items of power plant
1. Vacuum circuit breaker insulation resistance measurement, each phase circuit resistance measurement and AC voltage withstand tests of 10KV H.V. switch cabinet.
2. DC resistance measurement of CT and PT, polarity test, ratio test, AC voltage withstand tests in 10KV H.V. switch cabinet.
3. AC voltage withstand tests for whole 10KV H.V. switch cabinet.
4. AC resonant test for 10KV H.V. electric cable.
5. DC resistance measurement of generator stator and rotor.
6. Generator stator coil insulation resistance measurement and DC voltage withstand tests.
7. Generator rotor insulation resistance measurement.
8. Generator rotor AC impedance and power loss tests.
9. No-load characteristic test of generator
10. Generator checking phase sequence (fist checking phase and second checking phase separately).
11. Generator short circuit characteristic test.
12. Measurement of residual voltage of stator after automatic magnetic blow-out and switch opening of generator.
13. Generator shaft voltage measurement.
14. Generator simulate synchronization.
15. All of the second circuit checking, measuring, switch tripping & closing tests, protection fixed value setting, protecting the STG trip test and magnetic blow-out tripping test for Steam Turbine and generator.
III.Electrical problem troubleshooting in power plant
Problem Description: a coal mine`s 35KV H.T. switchgear OC protection tripped suddenly in He`nan Province, it caused sudden power lost of mine fan and endanger miner safety.
Auto-reclosing via switchgears` automatic reclosing function, through analysis, the reason is a set of 3000KW generator failure. Specific reason is: When the turbo-generator was running normally, exciting voltage lost suddenly, leading phase operation happened, the generator absorbed reactive power and lead to becoming motor running. Generator protection and power plant connecting line protection did not launch. After the generator absorbed a certain value of reactive power, the 35KV H.T. switchgear`s OC protection tripped.
Investigation: generator and power plant connecting line protection setting fixed value exceed the protection fixed value of 35KV switchgear side, it lead to nearby protection did not launch and override trip when generator failure.
Electrical Cabinet Care,10Kv Electrical Cabinet Care,0.4Kv Electrical Cabinet Care,Electric Governing Reconstructing
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