1.2.1 graded pilot
When the thundercloud electricity, either in the cloud or between the cloud to the ground, the electric field strength is not everywhere the same, when the cloud of a dense center of the electric field strength of a charge reaches (25 ~ 30) kV / cm, the beginning of corona discharge, which is the pilot stage of the lightning discharge, also known as the pilot discharge. First graded development, the average speed of about (1O. ~ lO.) m / s, each level of the arc, the length of about 50 m, the development speed of about 5 × 10 m / s, the pause time (30 "-90) ms, the pause time to complete the thundercloud on the pilot channel charging, strengthening the pilot head of the electric field to promote the next echelon of the development of the pilot, the development of the direction of grading the pilot is not selective.
1. 2. 2 main discharge and multiple discharges
When the graded pilot head from the ground (or buildings, etc.) distance of R, at a point on the ground to meet the lightning pilot, from the top down the development of graded pilot selected this point for the point of lightning strike, the people known as the distance from the strike, R and the lightning current. R = 6.71 (R unit: m; I unit: kA) When the two pilot head to meet, a strong neutralization discharge occurs, the current is called the distance. Occur strong neutralization discharge, the current is several thousand to tens of thousands of amperes, and even up to hundreds of thousands of amperes, thunder and lightning at the same time accompanied by the emergence of this discharge process in the form of a wave from the bottom up (is from the bottom upwards) propagation to the thundercloud, which is the main discharge stage of lightning, also known as the backlash. Strike back speed of about 1 / 3 speed of light, time is very short, about (50 ~ lOO) micro s. Thundercloud in the remaining charge in the afterglow phase discharge, lasts about 0.03 s.
1 thunder discharge development process
Since the cloud may exist at the same time a number of charge centers, so when the first center of the charge of the above discharge process is completed, may cause the second, the third center of the first channel discharge, so lightning is the first channel, so it may cause the second, the third center of the first channel, so it may cause the second, the third center to the first channel discharge. The first channel discharge, so lightning is often multiple, each discharge interval (0.6 ~ 800) ms, the average number of discharges for 2 ~ 3 times, up to 42 times. The second and subsequent discharge currents are generally smaller, not exceeding 30 kA.
Reference:
Thundering precautions:
Outdoor: do not carry out outdoor ball games, such as golf, soccer, etc.; do not swim or do other water sports; do not stay on top of the hill or high-rise platforms; in the open should not be entered into an isolated sheds, posts, etc.
2. Stay away from exposed water pipes, gas pipes and other metal objects in buildings and electrical equipment.
3. It is not advisable to take shelter from thunderstorms under large isolated trees. It is best to keep a distance of 5 meters from the trunk of the tree, squatting and legs close together, if you use your hands to hold the tree, as dangerous as using your hands to touch the lightning rod.
4. When you are standing in an open place, if you feel the hairs on your body suddenly stand up, your skin feels a slight tingling, or you even hear a slight popping sound, this is a sign that lightning is about to strike you. In this case, you should immediately squat down, lean forward, put your hands on your knees and curl them into a ball, and never lie flat on the ground.
5. When you are in the danger of a thunderstorm, stop walking, put your feet together and crouch down immediately.
6. When you go out in stormy weather, it is better to wear rubber shoes, which can serve as insulation.
7. It is not advisable to stay at the water's edge and depressions, because the water conducts electricity well and is vulnerable to lightning strikes.
8. It is not advisable to drive a motorcycle quickly, ride a bicycle fast and run wildly in the rain.
9. If you see a high-voltage line broken by lightning, you should be vigilant, because there is a high-voltage line near the point of breakage of the step voltage, people in the vicinity of the time do not run, but should be feet together, jump away from the scene.
10. Do not make or receive a cell phone when thunder, it is best to turn off the power of the phone
Indoor:
Indoor words, as long as you live in a house has to press the lightning rod, then it is very safe, but still need to pay attention to: do not turn on the TV, do not listen to the phone, do not surf the Internet.
Feet together, you can avoid stride voltage ah. What is stride voltage, you may ask.
When an overhead line of a live wire breaks down on the ground, the landing point and the potential of the live wire is the same, the current will be scattered from the landing point of the wire to the earth, so the ground to the landing point of the wire as the center, the formation of a distribution of potential area, the farther away from the landing point, the more the current is dispersed, the ground potential is also the lower. In the wire landing point 20 meters away, the ground potential is approximately equal to zero. Electric wire landing point as the center of the circle, drawing a number of concentric circles, an approximation of the potential distribution around the landing site. When a person in this area, two feet stand far from the landing point on a different position, there is a potential difference between the two feet, this potential difference is known as the step voltage. The higher the voltage of the landing wire, the closer to the landing point, the higher the step voltage.
Of course you can't watch TV when it's thundering. Everything related to electricity is best not to use, TV, telephone, computer will produce electromagnetic waves, thunder days, the current is easy to enter your house through electromagnetic waves (install lightning rods may be in a better condition) to destroy the TV, telephone, or computer you are playing. Last year, my aunt's TV was not turned on because the antenna was not unplugged, and it was damaged by lightning. And also, don't turn on the water heater, don't forget that water is very conductive.