Static electricity seems to be a joke to people who are not familiar with the Robert Van de Graaff generator. Today we will consider measures of protection against static electricity and tell why there are lightning. Then we apply some of the knowledge in practice in the oil industry. You will learn how to protect the antenna, why lightning always hits in one place. Due to static electricity, the discharge selects extremely tall trees on the plain. You can not hide at the foot of a tree during a thunderstorm. The topic of today's conversation is protection from static electricity.
Static electricity in nature
Everything flows - everything remains the same. Previously, it was necessary to protect the vacuum cleaner from static; today they simply use improved materials. There is always the possibility of charge accumulation. In this light, the protection of circuits from static electricity disturbs the minds. Electrostatic voltage used to be very suitable for entertaining the public and making profit from the lectures of professors. For example, scientists' minds had fun in this way:
- A homeless man was charged with static electricity by friction with a charge of a certain sign.
- Then the experimenter touched the subject's nose.
- A click of an electric discharge was heard, some of the money migrated to the homeless.
- As a result, everyone was satisfied: viewers who saw static electricity in action, a street kid who earned a piece of bread, and a professor who raised his own popularity.
Static electricity was noticed in Ancient Greece, but the first reliable description, like the mathematical model, was invented by Coulomb after centuries. Coulomb invented the concept of electric charge, explained the mechanics of the interaction of bodies with an excess of electrons or a disadvantage.
It turned out that dielectric materials, like ebonite sticks, concentrate an excess of positive or negative charges in a limited area. An explanation was given later. It turns out that in order to distribute the charges evenly over the surface, the material must have electrical conductivity. Similarly, metals were singled out into a single class. Then followed a series of discoveries on static electricity:
- It turns out that if you bring a charge closer to a metal object, the like ones flow to the opposite side. On the first there is an excess of carriers of the opposite sign.
Magicians to people uninformed showed an interesting phenomenon. The metal rod, isolated( for example, varnish) from static electricity, concentrated on a thin gold plate, reinforced at the bottom. When the maestro brought the “magic wand” rubbed on the rabbit to the opposite end of the axis, the petal rose. The spectators did not see - but before the experiment the plate of gold was charged with carriers of the desired mark( by friction).When the magic wand was approaching the rod, a potential difference was created at the ends. As a result, the plate, being suitably charged with static electricity, was repelled.
- A charge capable of switching between bodies.
On the example of the previous layout, the magician acted as follows: the wand was approaching the rod, then they touched. The surface charge density of static electricity was equalized( with proportion).At removal of a rod the plate all the same remained to hang in air. Can you imagine what impact static electricity produced on the audience? But the need for a security device is explained by the focus not even described.
- The third effect was able to hit the audience by Robert Van de Graaf( American physicist, 1901 - 1967).He invented an original device for forcing the potential of static electricity onto the surface of a steel ball.
Meaning: the conveyor belt rubbed on the glass and went along a circular path to the metal sphere. The moving material is a dielectric, the charge of static electricity is not lost anywhere. But the ball had a large surface, in addition, conducted a current. Due to what is happening, a small area of a highly charged tape began to give out carriers. And the sphere was charged with static electricity. Humorists and pranksters do not recommend touching such a thing, the standard methods of protection may not work: the curiosity potential exceeded 1 MW( megavolt, million volts).As a result, a Van de Graaff generator was created, reaching 7 MB.
- Protection of pipelines in the oil business was not required because of the ability of bodies( pipes) to transfer or receive a charge. With some field strength( potential difference), static electricity poured into a thunderstorm.
As you know, lightning is caused by the ionization of air molecules at points between charged parts. There is a plasma path. The similarity of air electrolyte. He transfers charges, so arises arc( welder).
. Lightning protection is on every plane: there are devices in the rear part of the wing that end in a heap of thinnest steel wires, while landing, the machine does not strike the line with lightning( which easily leads to an explosion).Instead, an excess of carriers forms a spark and flows back while the aircraft is moving in the form of a plasma. Such measures are actively used by motorists, but the surplus is given to the Earth. Our planets are electrically conductive, willingly accept static charges to spread them across the surface, then the process fades away, compensated by winds, waters, losses in the thickness of the soil and other effects.
Measures against static electricity
Actually, the protection of equipment from static electricity has already been partially considered. These are vehicle glaziers. Often used cut rubber, but works only in wet weather. When the car goes on the road, rubbing with dust and air molecules provokes the appearance of a static charge. Dry rubber dielectric flowing off is ineffective. In wet weather, the problem is solved completely. At the same time, the risk of injury to humans is low in a dry environment, and rubber is more often lacking.
When protection against static electricity at work is organized, they are guided by standards. For example, oilmen refer to the resolution of the Gosgortekhnadzor of 20.05.2003.Documents state that any equipment with a metal casing and any type of paint is considered to be protected when grounded. In this case, the resistance to the input to the local circuit bus is not more than 10 ohms. Check the computer with a tester and a properly equipped outlet.
Make sure that the resistance from the far point of each plate of the system unit to the side lobe does not exceed 10 Ohms. By the way, according to the specified standards, the circuit must fit into the frame up to 5 ohms relative to the globe. Grounding is a residential cross-section of 6 square millimeters of copper or 10 on aluminum. Take note if you want to protect yourself from lightning and static electricity at the same time. According to the standards of the TN-S-S group standards, it is allowed to connect the grounding in the house( under the foundation) to the lightning protection circuit.
What is often done in practice. ESD cable is well known. For employees of workshops and laboratories associated with computer equipment, the protection measures described are not limited. It is allowed to buy special plates for the floor, but at home it is easier to restrict yourself to dialing:
- The means of protection against static electricity begin with the presence of a ground terminal at the workplace. This is a tap in the form of a bolt with a nut, an eye for connecting a number of devices.
- People dealing with microcircuits usually wear special antistatic bracelets on both hands. Woolen sweaters are prohibited, but the additional charge formed is intended to immediately drain.
- Special shoes( sole material) prevents the accumulation of static charge. If you work with expensive chips, spend a couple of thousand rubles to save( protect from loss) millions.
- As for large enterprises, the rules for protection against static electricity in manufacturing often require the use of in-depth steps. On sale there are trousers, jackets and suits made of special fabric. Such an employee is no longer a thunderstorm for sensitive electronic equipment. Such a set is often cheaper than an employee’s daily clothes( sometimes not as good as a pair of decent sneakers).There are insulated options for the cold conditions of the North( do not forget about the oil industry workers).
Antennas often stand on the roof, protection is required first. Due to the friction of clouds and winds in the atmosphere, static electricity is accumulated. The charge density is the same of constant movement of air masses. Ionization occurs where the distance to the sky is less. These are the peaks of the trees. When it comes to the city, the roofs of high-rise buildings become targets. For this purpose, lightning conductors are made. Peak device must exceed all the items on the roof.
The characteristics of lightning protection are discussed in RD 34.21.122С.Discussed potential drift to the floors along the pipe path, metal braid cables. To exclude the phenomenon, the specified objects at the basement level are combined with grounded reinforcement of the foundation. If this is not possible, additional actions are carried out:
- According to section 2.2 g of the RD 34.21.122C, an outline is equipped.
- Consists of three vertical rods not shorter than 3 m with a distance of 5 m between them.
- The section of the contour elements is determined by table 3 of the section under discussion: the gradation is conducted depending on the location and shape. The underground part is assembled from round electrodes with a diameter of at least 10 mm. Rectangular are selected by section in square millimeters( 40 outer, 100 underground), and the reinforcement thickness is not less than 4 mm. Finally, round tokovody above the soil surface is not thinner than 6 mm.
The above information is enough to understand: the ground loop in comparison with the recommendations of gardeners on YouTube is not. In reality, everything is much more complicated. Methods of protection of integrated circuits are performed according to GOST, and not according to the recommendations of neighbors. By the way, a cap is relied on the head so that hair does not fall, and bracelets are put on both hands.
Instead of an
ESD protection statement. It happened that the graphics adapter burned out from touching the monitor. The VGA adapter burned out, as expected, when tested. A potential was applied to the kinescope, and a charge was also present outside. We believe that the rules of protection against static electricity now bounce off readers' teeth.