Static electricity seems like a joke to people unfamiliar with the Robert van de Graaff generator. Today we will look at measures to protect against static electricity and tell you why lightning occurs. Then we will apply some of the knowledge in practice in the oil industry. You will learn how the antenna is protected, why lightning always strikes in one place. Thanks to static electricity, the discharge picks up exceptionally tall trees on the plain. You cannot hide at the foot of a tree during a thunderstorm. The topic of today's conversation is protection against static electricity.

Static electricity in nature

Everything flows - everything remains the same. Previously, it was required to protect the vacuum cleaner from static, today they simply use improved materials. There is always the possibility of accumulating charges. Seen in this light, the protection of microcircuits from static electricity worries minds. Electrostatic stress was previously well suited to entertain the public and profit from the lectures of professors. For example, learned minds have fun in this way:

  1. The homeless child was charged with static electricity by friction with a charge of a certain sign.
  2. Then the experimenter touched the subject's nose.
  3. There was a click of an electric discharge, part of the money was transferred to the homeless child.
  4. As a result, everyone was happy: the audience who saw static electricity in action, the street child who earned a piece of bread, and the professor who raised his own popularity.

Static electricity was noticed in Ancient Greece, but the first reliable description, like a mathematical model, was invented by the Pendant after centuries. Coulomb invented the concept of electric charge, explained the mechanics of interaction of bodies with an excess of electrons or a deficiency.

It turned out that dielectric materials, like an ebonite rod, 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. In a similar way, metals were singled out into a single class. Then a series of discoveries on static electricity followed:

  • It turns out that if you bring a charge closer to a metal object, the same names flow to the opposite side. On the first, there is an excess of carriers of the opposite sign.

Magicians demonstrated an entertaining phenomenon to ignorant people. A metal rod, isolated (for example, with varnish) from static electricity, concentrated on a thin gold plate, reinforced in the lower part. When the maestro brought the "magic wand" rubbed against the rabbit to the opposite end of the axis, the petal rose. The audience did not see - but before the experiment, the gold plate was charged with the carriers of the desired sign (by friction). When the magic wand approached the rod, a potential difference was created at the ends. As a result, the plate, being appropriately charged with static electricity, was repulsed.

  • The charge is capable of transferring between bodies.

Using the example of the previous layout, the magician acted as follows: the wand approached the rod, then they touched. The surface density of charges of static electricity was equalized (with proportion). When the wand was removed, the plate still hung in the air. Can you imagine what effect static electricity produced on the audience? But the need for a protection device is explained even by a trick that is not described.

  • The third effect was able to amaze the audience Robert Van de Graaf (American physicist, 1901 - 1967). He invented an original device for injecting a potential of static electricity onto the surface of a steel ball.

Meaning: the conveyor belt rubbed against the glass and followed a circular path to the metal sphere. The moving material is dielectric, the charge of static electricity is not lost anywhere. But the ball had a large surface, and in addition it conducted current. Due to what was happening, a small section of a highly charged tape began to give away media. And the sphere was charged with static electricity. We do not recommend humorists and pranksters to touch such a little thing, standard methods of protection may not work: the potential of the curiosity exceeded 1 MV (megavolt, million volts). As a result, the Van de Graaff generator was created, reaching 7 MV.

  • The protection of pipelines in the oil business was not required because of the ability of bodies (pipes) to transmit or receive a charge. At a certain field strength (potential difference), static electricity poured out into a thunderstorm.

As you know, lightning is caused by the ionization of air molecules at points between charged parts. A plasma path appears. Similar to an airborne electrolyte. It transfers charges, so an arc (welder) arises.

Lightning protection is installed on every aircraft: in the rear part of the wing there are devices ending in a heap of the finest steel wires, landing, the car does not hit the strip with lightning (which easily leads to an explosion). Instead, the excess of carriers forms a spark and flows back as the aircraft moves in the form of plasma. Similar measures are actively used by motorists, but the surplus is given to the Earth. Our planet is electrically conductive, willingly accepts static charges in order to spread them over the surface, then the process fades away, is compensated by winds, water, losses in the soil and other effects.

Anti-static measures

Actually, the protection of equipment from static electricity has already been partially considered. These are vehicle drainers. A piece of rubber was often used, but only works in wet weather. When the car is driving on the road, the friction of dust and air molecules creates a static charge. Dry rubber is a dielectric, draining is ineffective. In wet weather, the problem is solved completely. At the same time, the risk of injury to a person is low in a dry environment, and there is often enough rubber.

When organizing the protection against static electricity in production, they are guided by the standards. For example, oilmen refer to the Gosgortekhnadzor resolution dated 20.05.2003. The documents state that any equipment with a metal case and any type of paintwork is considered protected by being grounded. In this case, the resistance to the entrance to the local loop bus is not more than 10 ohms. Test your computer with a tester and a properly equipped outlet.

Make sure that the resistance from the farthest point of each plate of the system unit to the side lobes does not exceed 10 ohms. By the way, according to the specified standards, the circuit must fit into a frame of up to 5 ohms relative to the Earth. Grounding is carried out with a residential cross-section of 6 square millimeters for copper or 10 for 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-C-S group, it is allowed to connect grounding in the house (under the foundation) to the lightning protection circuit.

Which is often done in practice. An ESD cable is known. For workers in shops and laboratories associated with computer technology, the protection measures described are not limited. It is allowed to buy special floor slabs, but at home it is easier to limit yourself to a set:

  1. ESD protection starts with a grounding lug in the workplace. This is a branch in the form of a bolt with a nut, an eyelet for connecting a number of devices.
  2. People who work with microcircuits, as a rule, wear special antistatic bracelets on both hands. Woolen sweaters are prohibited, but the additional charge generated is intended to drain immediately.
  3. Special footwear (sole material mainly) prevents the build-up of static charges. If you work with expensive microcircuits, spend a couple of thousand rubles to save (save from loss) millions.
  4. For large factories, ESD regulations in manufacturing often require advanced steps. On sale there are trousers, jackets and suits made of special fabrics. Such an employee is no longer a thunderstorm for sensitive electronic equipment. Such a set is often cheaper than the employee's daily clothing (sometimes it does not hold up to a pair of decent sneakers). There are insulated options for the cold conditions of the North (don't forget about the oilmen).

Antennas are often located on the roof, protection is required first of all. Static electricity builds up in the atmosphere due to the friction of clouds and winds. The density of charges is the same from the 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 targets are the rooftops of high-rise buildings. For this purpose, lightning rods are made. The peak of the device must exceed all objects on the roof.

Features of the organization of lightning protection are discussed in RD 34.21.122C. Potential drift to floors along the path of pipes, metal braiding of cables is discussed. To exclude the phenomenon, these objects at the basement level are combined with the grounded reinforcement of the foundation. If this is not possible, additional steps are taken:

  • According to clause 2.2 g of RD 34.21.122C, a circuit 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: gradation is carried out depending on the location and shape. The underground part is assembled from round electrodes with a diameter of at least 10 mm. Rectangular ones are chosen according to the section in square millimeters (40 external, 100 underground), and the thickness of the reinforcement is at least 4 mm. Finally, round current leads above the soil surface are not thinner than 6 mm.

The given information is enough to understand: the ground loop does not go to YouTube in comparison with the recommendations of gardeners. In reality, everything is much more complicated. Protection methods for integrated circuits are carried out in accordance with GOST, and not according to the recommendations of neighbors. By the way, a hat is placed on the head so that the hair does not fall, and bracelets are worn on both hands.

Instead of a conclusion on protection against static electricity

It happened that the graphics adapter burned out from touching the monitor. The VGA adapter burned out as expected during the test. A potential was applied to the kinescope, and there was also a charge outside. We suppose the rules of protection against static electricity are now bouncing off the teeth of readers.

To eliminate harmful and dangerous manifestations of static electricity, the following measures are used: grounding of industrial equipment cases; grounding of tanks for storage and transportation of flammable and combustible liquids; antistatic surface treatment; the introduction of antistatic substances into the composition of products; an increase in the moisture content of the processed materials and the environment; ionization of the medium; reducing the speed of processing materials.

Grounding is mandatory and applies even to the detriment of the technological process. This method is traditional and the most widespread. Cases of devices and mechanisms, tips of drain hoses, vehicles for transporting fuels and lubricants (fuel trucks), etc. are grounded. Grounding is carried out according to the rules for grounding electrical installations. However, here the grounding resistance should not exceed 100 ohms.

Grounding is, although a reliable method of protection, but not always, since it dissipates to the ground only a part of the charge accumulated on electrically conductive equipment housings, and charges accumulated on dielectric materials and parts of equipment can persist for a long time and create a risk of spark discharges.

Since an increase in humidity significantly reduces the accumulation of charges, this method of protection is also widely used. So, in the industry during the production and processing of synthetic fibers, it is recommended to maintain the humidity at the level of 85 - 90% as optimal. However, it should be borne in mind that there are materials that cannot be processed at high humidity or the quality of which may decrease. Therefore, this method is not always applicable.

Antistatic surface treatment using certain chemical compositions increases the electrical conductivity of these surfaces and reduces the likelihood of charging them or even prevents them from electrifying. In addition, many of these materials have good lubricating properties and reduce friction, and can also be hygroscopic, which can reduce electrification. Antistatic substances are also introduced into the composition of products. For example, in the manufacture of hoses for loading and pumping flammable liquids, graphite and soot are added to the material. Sometimes antistatic additives are added to the composition of liquids, which increases their electrical conductivity. However, this method has not yet found widespread use in all industries where there is a risk of static electricity. For example, in the powder industry, it is only used for certain material combinations.

A reliable method of neutralizing static electricity is to create electrical charges of opposite polarity and direct them towards a charged object.


When the charges are recombined, the desired neutral state is achieved. This protection method is widely used in industry. Depending on how the charge (ions) is generated, the methods differ from each other. Of the many ways to create ions in air, the following two are of practical importance: air ionization by means of a controlled corona discharge; ionization of air using X-ray, gamma and ultraviolet radiation, as well as a- and b-particles.

As an example, consider a schematic diagram of an apparatus for neutralizing static electricity, in which a corona discharge is used to generate electric charges (Fig. 2.3). In this case, the charges are neutralized on a synthetic tape 3, which is driven by rollers 1 and 2. The ionizer 4, which is under a high voltage of the opposite polarity to the charges of the electrified tape, creates a corona discharge. Discharge electric current, i.e. the number of charges moving towards the material increases with increasing voltage. Thus, the charges

going to the electrified material will compensate its charges up to the required value. The presence of polarity and the number of charges on the material are controlled by an electrometer 7. By adjusting the voltage with the regulator 5 until the readings of the electrometer become equal to zero, it is possible to achieve complete neutralization of the charges. Since a charge can also accumulate on the inner surface of the tape, it is possible to use another ionizer located below the tape for complete neutralization. However, it has been experimentally proven that one ionizer is enough for almost complete neutralization.

Rice. 2.3. Schematic diagram of an apparatus for neutralizing static electricity

The design of radioactive neutralizers is quite simple and usually have the form of a long plate or disk with a radioactive preparation deposited on one side. The most commonly used solutions are radium (Ra) and polonium (Po). Radium emits particles a and b with a half-life of T 1/2 = 1590 years, and polonium - particles a with a half-life of T 1/2 = 138 days. Radiation a consists of helium particles with a charge of 2e + and a penetration depth of 30 - 75 mm in air. Radiation b consists of electrons and has a penetration depth of 1 m for radium. Gamma radiation, in comparison with a- and b-particles, has a lower penetrating power.

Radioactive ionizers are positioned at such a distance from the body to be neutralized that maximum efficiency is achieved. It should be noted here that it is rather difficult to regulate the amount of generated charges (ions) in this type of neutralizers, and, as a rule, there is no such adjustment.

Lecture 11. Protection against exposure to industrial radiation

The widespread use in all areas of economic activity of dielectric materials and organic compounds (polymers, paper, solid and liquid hydrocarbons, petroleum products, etc.) is inevitably accompanied by the formation of static electricity charges, which not only complicate technological processes, but also often cause fires and explosions causing great material damage. This often leads to the death of people.

Static electricity is a set of phenomena associated with the emergence, conservation and relaxation of a free electric charge on a surface, or in the bulk of dielectrics, or on insulated conductors (GOST 12.1.018). The formation and accumulation of charges on the processed material is associated with the following two conditions:

♦ the presence of contact between surfaces, as a result of which a double electric layer is created, the occurrence

which is associated with the transition of electrons in elementary donor-acceptor acts on the contact surface. The sign of the charge determines the unequal affinity of the surface material for the electron;

♦ at least one of the contacting surfaces must be made of a dielectric material.

The charges will remain on the surfaces after the termination of contact only if the time of contact destruction is shorter than the relaxation time of the charges. The latter largely determines the magnitude of the charges on the separated surfaces.

Mixed charging occurs when electrified material enters any container that is isolated from the ground. This type of charging is most often encountered when pouring flammable liquids into containers, when feeding rubber adhesives, fabrics, films into mobile containers, carts, etc. The formation of static electricity charges upon contact of a liquid with a solid or one solid with another largely depends on the density of contact of the rubbing surfaces; their physical state, speed and coefficient of friction, pressure in the contact zone, microclimate of the environment, presence of external electric fields, etc.

Static electricity can also build up on the human body (during work or contact with electrified materials and products). The high surface resistance of human tissues makes it difficult for the charges to flow out, and a person can be under great potential for a long time.

The main danger in the electrification of various materials is the possibility of a spark discharge from both a dielectric electrified surface and an insulated conductive object.

In addition to a fire hazard, static electricity is also a hazard to workers.

Light "pricks" when working with highly electrified materials have a detrimental effect on the psyche of workers and, in certain situations, can lead to injuries on technological equipment. Strong sparks, such as when filling granular materials, can cause pain. Unpleasant sensations caused by static electricity can be the reasons for the development of neurasthenia, headache, poor sleep, irritability, tingling in the heart, etc. In addition, with the constant passage of low electrification currents through a person's body, unfavorable physiological changes in the body are possible, leading to occupational diseases. The systematic effect of an electrostatic field of increased intensity can cause functional changes in the central nervous, cardiovascular and other systems of the body.

The use of artificial or synthetic fabrics for clothing also leads to the accumulation of static electricity on a person. GOST 29191 (IEC 801-2-91) provides information that synthetic fabrics can be charged up to a potential of 15 kV. Therefore, the current flowing through the body of a person wearing a suit or robe made of synthetic fabric can reach 3 μA. Touching grounded parts of the workplace or an uncharged body will cause a spark discharge with amperage up to 30 A.

Static electricity also strongly affects the course of technological processes for the production and processing of materials and the quality of products. At high charge densities, an electrical breakdown of thin polymer films for electrical and radio engineering purposes can occur, which leads to a rejection of the manufactured product. Particularly great damage is caused by the adhesion of dust to polymer films caused by electrostatic attraction.

Electrification complicates such processes as sieving, drying, pneumatic transport, printing, transportation of polymers, dielectric liquids, the formation of synthetic fibers, films, etc., automatic dosing of fine materials, since they stick to the walls of technological equipment and stick together.

Permissible levels of intensity of electrostatic fields are established by GOST 12.1.045 and SanPiN 11-16-94.

Protective equipment against static electricity should be used in all explosion and fire hazardous rooms and areas of open installations, classified according to the PUE classification to classes BI, B-Ia, B-I6, V-1g, V-P, V-Tsa, P-I , P-P.

When organizing production, you should avoid processes accompanied by an intensive generation of static electricity charges. To do this, it is necessary to correctly select the friction surfaces and the speed of movement of substances, materials, devices, avoid the processes of spraying, crushing, spraying, clean flammable gases and liquids from impurities, etc.

An effective method for reducing the rate of generation of static electricity is method of contact pairs. Most of the structural materials for dielectric constant are located in triboelectric rows in such a sequence that any of them acquires a negative charge upon contact with the next material in the row and a positive charge with the previous one. Moreover, with an increase in the distance in a row between two materials, the absolute value of the charge arising between them increases.

To prevent the possibility of accumulation of static electricity on the surfaces of equipment, processed materials, as well as on the body of combustible mixtures working above the minimum ignition energy, it is necessary, taking into account the peculiarities of production, to ensure that the emerging charges drain from charged objects.

In accordance with GOST 12.4.124, this is achieved by using collective and individual protective equipment.

According to the principle of action, collective protection means against static electricity are divided into the following types: grounding devices, neutralizers, humidifying devices, anti-electrostatic substances, shielding devices.

Earthing refers to basic methods of protection against static electricity and is the deliberate electrical connection to earth or its equivalent of non-conductive metal parts that may be energized. It is the simplest, but necessary means of protection due to the fact that the energy of a spark discharge from conductive ungrounded elements of technological equipment is many times higher than the energy of a discharge from dielectrics.

The resistance value of the grounding device, designed exclusively for protection against static electricity, must not exceed 100 ohms.

Particular attention must be paid to the grounding of mobile objects or rotating pieces of equipment that are not permanently in contact with the ground. For example, mobile containers into which electrifying materials are poured or poured must be installed on grounded bases before filling or connected to a ground electrode with a special conductor before the hatch is opened.

Neutralization of charges static electricity is produced in cases where it is not possible to reduce the intensity of its formation by technological and other methods.

In some cases, it is effective to use beam neutralizers static electricity, which provide ionization of a material or medium under the influence of ultraviolet, laser, thermal, electromagnetic and other types of radiation.

The removal of static electricity charges by reducing the specific and surface electrical resistance is used in cases where the equipment grounding does not prevent the accumulation of charges to a safe value.

To reduce the specific surface electrical resistance of dielectrics, the relative air humidity can be increased to 65-70%, if this is permissible under the production conditions. For this purpose, general or local humidification of the air in the room is used with constant control of its relative humidity. In this case, an electrically conductive water film forms on the surface of solid materials, through which static electricity charges are discharged to grounded technological equipment.

To reduce the specific volumetric electrical resistance in dielectric liquids and solutions of polymers (adhesives), various soluble in them are introduced anti-electrostatic additives (antistatic agents), in particular, salts of metals of variable valence of higher carboxylic acids, naphthenic and synthetic fatty acids. These additives include Sigball, ASP-1, ASP-2, as well as additives based on chromium, cobalt, copper oleates, naphthenates of these metals, chromium salts, etc. Abroad, the most widely used additives are those developed by Ekko and Shell (additive ASA-3).

To do this, use electrically conductive floors made of materials in which the specific volumetric electrical resistance should not be higher than 10 6 Ohm × m. Non-conductive coatings include asphalt, rubber, linoleum, etc. Conductive coatings are concrete, foam concrete, xylene, etc. Grounded platforms and work platforms, door handles, stair handrails, handles of devices, machines, mechanisms, apparatus are additional means of removing charges from the human body.

Personal protective equipment against static electricity includes special electrostatic shoes and clothing. For the manufacture of such clothing, materials with a specific surface electrical resistance of not more than 10 7 Ohm × m should be used, and the electrical resistance between the conductive element of anti-electrostatic clothing and the ground should be from 10 6 to 10 8 Ohm. The electrical resistance between the center pad and the running side of the sole of the shoe should be between 10 6 and 10 8 ohms.

In some cases, the continuous removal of static electricity from a person's hands can be carried out using special grounded bracelets and rings. At the same time, they must provide electrical resistance in the human-earth circuit from 10 6 to 10 7 ohms and freedom of movement of the hands.

Protection against electromagnetic fields (EMI)

In production, electromagnetic fields of radio frequencies and industrial frequencies, permanent magnetic and electrostatic fields are widely used, the danger of which is aggravated by the fact that they are not detected by the senses. They are used to heat metal during melting and forging, to obtain a plasma state of a substance, during heat treatment of various materials, in radio and electronic devices. The degree and nature of the effect of EMF on the human body is determined by the energy flux density, radiation frequency, exposure duration, exposure modes (continuous, long-term), the size of the irradiated body surface, individual characteristics of the body, combined action together with other harmful factors of the working environment (increased ambient temperature , the presence of X-rays, noise, and more).

In the area of ​​EMF action, a person is exposed to thermal and biological effects: overheating, eye irradiation, functional changes in the central nervous and cardiovascular systems (headaches, fatigue, deterioration of health, neuropsychic disorder, etc.), trophic disorders can be observed: weight loss, loss hair, brittle nails, change in blood.

Means and methods of protection: reducing radiation parameters directly in the radiation source itself, shielding radiation sources, shielding the workplace, limiting the time spent by personnel in the EMF area, increasing the distance between the radiation source and the workplace, using warning alarms, using personal protective equipment, etc. ...