Static electricity voltage. Static voltage. What is static electricity

Static electricity refers to a set of phenomena associated with the appearance of electrical charges on the surface of dielectrics or isolated conductive bodies and their various manifestations. The formation of static electricity is based on very complex processes that depend on many factors. Currently, there is no single theory explaining static electrification, but there are a number of hypotheses. What they have in common is the proposition that during electrification, a double electric layer is formed, which serves as a direct source of static charges (L. Loeb, 1963).

The hypothesis of contact electrification of matter is most widespread. According to this hypothesis, electrification occurs when two different substances come into contact due to the imbalance of atomic and molecular forces on the contact surface. In this case, a redistribution of electrons or ions of the substance occurs and the formation of a double electrical layer (one on each surface) with opposite signs. Such electrification is observed when a metal comes into contact with a semiconductor or dielectric, rubber and other bodies (J. Staroba, J. Shimorda, 1960). The magnitude of the contact potential difference is not the same and depends on the dielectric properties of the contacting surfaces, the state of the surface, the pressure between them, as well as on humidity and temperature. When surfaces are separated, each surface retains its charge.

According to other hypotheses, static electrification is caused by the effects of impact and separation; surface orientation of neutral molecules containing electric dipoles; piezoelectric phenomena during friction, the formation of electrolytes on contacting surfaces and other processes. It has been experimentally established that electric charges accumulate on the surface of contacting materials, the dielectric constant of which is different. Positive charges accumulate on the surface of a material whose dielectric constant is greater. An uncharged, electrically neutral body means the presence at the same time in equal quantities of two opposite types of charges.

The appearance of electric charges on bodies is accompanied by the appearance of a static electric field (SEF), in which they interact with each other. Negative electrification, i.e., an excess of electrons in the polymer, cannot cause electron mobility in molecules and their redistribution in volume. Due to excess free electrons, with a decrease in the interaction of positively charged particles, additional chemical bonds can form and various chemical reactions can occur.

IN last years got wide application in everyday life and various branches of technology, synthetic polymers. These are clothes, linen, shoes, plastic coverings, latex and polyvinyl chloride mats, polyethylene dishes, car bodies, ships, aircraft, and various equipment. Synthetic polymers are a dielectric on the surface of which an electrical charge accumulates. A person may not be aware that electrical charges are distributed on his body, but if a lot of charges have accumulated, he can feel their presence by touching a metal object, for example, a water tap or a steam heating radiator. In this case, the person will feel an electric shock.

Electrification is especially strong when rubber shoes with synthetic soles come into contact with rubber tracks, plastic floor coverings, and when clothing rubs against the body (K. A. Rapoport, 1965). When performing various production operations or walking on a carpet, electrical charges of up to 10-15 kV can arise on the surface of the human body. Some types of clothing made from synthetic fabrics also generate large charges of static electricity - about 3000-5000 V/cm.

In the chemical, textile, printing and many other industries, during any technological process where there is dynamic interaction (mixing, spraying, moving through pipes, crushing, separation, mechanical processing of dielectric materials, etc.) on the surface of the equipment and the processed material, electrical charges. The resulting SEPs have a negative effect on the flow production process and product quality.

Electric charges cause mutual repulsion similarly charged threads, sticking of sheets of paper, dielectric film. Significant difficulties arise in the production, processing, packaging and transportation of synthetic materials.

In some cases, charges quickly flow into the ground, dissipate and neutralize, in others they accumulate on individual elements of equipment. In this case, high-voltage electrical power cells are created, causing electrical discharges. In explosive industries involving the use of flammable and combustible liquids, combustible gases and dusts, spark discharges of static electricity can cause explosions and fires, leading to significant losses, injuries or casualties.

The spark discharge mechanism resembles the phenomena of atmospheric electricity. Possessing energy millions of times less than lightning, discharges of static electricity can nevertheless ignite any flammable mixture formed or present in production processes.

Where flammable media are used, humans pose a real danger of ignition from static electricity discharges. With constant contact with charged equipment or material, as well as when walking on plastic floors, the human body, being a good conductor, accumulates electrostatic charges. The potential difference between the human body and surrounding objects can reach enormous values ​​- tens of thousands of volts. And as soon as such an electrified person approaches metal grounded structures, a spark discharge occurs.

With an average human electrical capacitance of 200 pF and a body potential relative to ground of 10,000 V, the discharge energy will be 10 mJ. This is many times more than the energy required to ignite or explode a number of explosives, as well as steam and gas-air flammable mixtures. For example, to ignite the most sensitive to thermal impulse air mixtures of hydrogen, methane or benzene, a spark discharge energy of 0.02, 0.33, 0.55 mJ is required, respectively.

Static electricity and explosions can also occur when transporting bulk products or liquids through pipelines made of polymer materials. The appearance of charges during the movement of a liquid is explained by a hypothesis suggesting that a double electric layer is formed at the interface between the liquid and solid phases. Any molecule located inside a liquid volume experiences the influence of van der Waals and Coulomb forces from the molecules. In this case, the action of all forces is mutually balanced, while the molecules located in the boundary layer are acted upon by unbalanced forces directed towards the interface, creating a force and electric field. Molecules oriented in this field form a double electric layer - negatively charged particles are located on the outside of the liquid layer, positively charged particles are located on the inside.

If the equilibrium of the double layer is disturbed, as is observed during the movement of a liquid, spatial separation of charges occurs, as a result of which the surfaces of the pipelines and the liquid become charged with electricity of the opposite sign. The amount of electric charge generated increases in inverse proportion to the fluid flow speed, roughness and length of the pipe. Large accumulations of charges are observed in places of increased dynamic resistance, i.e. when liquid comes out, at turns, in narrowings, expansions, etc.

Experiments have shown that the speed of transportation through pipelines of flammable liquids with high electrical resistance of the order of 10-10 Ohms should not exceed 1 m/s in order to avoid the accumulation of dangerous potential. For acetone, the flow speed should be no higher than 10 m/s.

Static electricity discharges do not pose a mortal threat to human life: they are either short-lived or have low currents. However, they have a physiological effect on the human body. Frequent discharges of static electricity cause nervousness among workers, which sometimes leads to disruption of technological regimes and a decrease in labor productivity. As a result of the muscular reaction caused by electrical shocks, mechanical injuries from moving and poorly protected parts of the equipment are possible. There have been cases of people falling from heights when receiving shocks from a discharge of static electricity.

The formation of static electricity on synthetic materials leads to rapid contamination of their surface. In this regard, certain inconveniences arise when using furniture, lighting fixtures, household items made of plastic, etc.

It has been established that the contamination of clothes made of synthetic fiber is 300-500 times greater than clothes made of cotton fabric. When wearing such clothes made of synthetic fabric, a person’s microclimate quickly deteriorates, resulting in impaired skin respiration, heat exchange, etc.

The electrification of synthetic materials promotes a more intensive release of their constituent components (V.A. Tsendrovskaya, A.M. Shevchenko, 1969) and increases the rate of their chemical destruction. The danger of static electricity formed on the surface of polymers also lies in the fact that the volatile toxic substances released from them, acquiring potential, more easily penetrate the body.

Scientists in many countries are now busy with the problem of combating electrification. But it turns out that not every electrification needs to be destroyed. Thus, the Earth’s SEP constantly affects the vital functions of the body, but isolating a person from this field will adversely affect his well-being. An example is the poor health of some people during travel in all-metal carriages and airplanes, when the Earth's SEP is shielded by a metal body (Yu. Morozov, 1969).

To measure electrostatic charges in natural conditions, various measuring instruments are used, the use of which depends on the type of synthetic material and the environment. To measure the magnitude of the potential accumulated on polymer materials, a device was created in laboratory conditions that simulates the main factors - friction speed, load on material samples (K. I. Stankevich, V. A. Tsendrovskaya, 1970).

The degree of electrification of polymer materials largely depends on chemical composition and electrically conductive properties. For example, the electrification of polyvinyl chloride (PVC) boards on latex resin is more than 20 times less than on suspension resin. PVC plates made with a mixture of latex and suspension resins have a low degree of electrification. Plastics containing fillers with hydrophilic properties have the lowest electrification properties.

Humidity has a significant effect on the electrification of polymer materials (Fig. 1). At a humidity of 60-80%, the charge value decreases by 2-3 times. At a humidity of 80%, a monomolecular layer is formed, which causes the material to lose its ability to accumulate charges of static electricity on the surface. A decrease in moisture content in the air leads to an increase in the conductivity of the polymer material.

Water adsorbed on the surface of the material is desorbed when the humidity of the environment changes, and the sample retains its dielectric properties for several months. However, when stored in air for a long time, the ability of plastics to accumulate charges of static electricity decreases. This appears to be due to destructive changes

Rice. 1.

Accumulated on polymers from ambient humidity.

Rice. 2.

Accumulated on polymers, at relative humidity: A - 30%, B, C - 50%, D, D - 60%. material under the influence of not only water, but also other environmental factors.

There is also a certain mathematical relationship between the amount of charge accumulated on the polymer material and the ambient temperature (Fig. 2). The dependence of the charge on temperature is inverse: with a decrease in temperature at the same humidity, an increase in charge is observed. However, the effect of temperature on the charge value is much less pronounced than that of humidity.

For some synthetic materials, such as nylon-based clothing, the temperature dependence can be expressed by the following formula (Capt James, 1963):

Where Q is the amount of charge;

A and B = constant values;

T - air temperature.

When studying clothing in the Far North, it was confirmed that calculations using this formula can be carried out to determine electrification at temperatures from -45 to 10 ° C. Knowing the magnitude of the charges at two temperatures, it is possible to calculate the magnitude of the charge arising at any other temperature.

Of the polymers used for floor coverings, PVC linoleum and slabs have the greatest electrification properties. At an air humidity of 15-30%, the charge on PVC linoleum floor coverings can reach about 2000 V. At relative air humidity and a temperature of 20±3°C, a stable field of static electricity appears, the magnitude of which depends on the presence and nature of electrical equipment. In rooms with parquet floors, the field strength at the floor surface and on the human body does not exceed 50 V/cm. At the same time, in rooms with a large amount of equipment on the floor surface covered with PVC linoleum, the charge reaches several tens of kilovolts. When walking on these floors, charges of up to 40 kV or more accumulate on the workers’ bodies. Relin, nitrolinoleum, and coumaron plates have lower electrical properties.

Studies of the electrification of floor coverings made of polymer materials under natural conditions in different climatic zones of the USSR have shown that the amount of static electricity charge varies mainly within the range of 300-500 V/cm. Sometimes it reaches 1500-2000 V/cm at low air humidity (20-25%), mainly on imported plastics, the binder content of which is about 50% of the total mass of the material. The opinion that in the conditions of the Arctic and Kazakhstan, where the relative humidity of the atmospheric air is low (10-20%), the electrification of floor coverings made of polymer materials reaches tens of kilovolts, was not justified. This is due to the fact that low relative humidity is observed only in the open atmosphere, and indoors it is leveled in all climatic zones.

A mass survey of the population living in premises with plastic floor coverings revealed that complaints about the effects of static electricity mainly boil down to headaches, fatigue, and pain in the heart.

The type of sole material of shoes is of significant importance when electrifying plastic floor coverings. Of the 9 (VMSh, leather, BS, BM, VM, vulcanite, leather, leather fiber, felt) sole materials, the highest electrification of PVC linoleum at 60% air humidity is caused by VMS leatherette (1400 V), and the lowest by felt (710 V) .

The magnitude of the charge arising during friction makes it possible not only to judge the influence of the electrostatic field in the hygienic aspect, but also to assess the degree of electrification compared to the potential. The magnitude of the potential is determined using a voltmeter (kilovoltmeter) and depends on its capacity. Therefore, the same potential value recorded with a voltmeter corresponds to different amounts of electricity on the surface under study.

Washing floors, equipment, washing clothes, etc. has a great influence on the level of electrification of polymer materials. It has been established that after a single wetting and drying of samples for 15 minutes, the amount of charge on their surface decreases by 2-3 times, and after repeated wetting and drying for 14 days - 10-12 times. Consequently, under operating conditions after repeated and prolonged treatment of the surface with water, their ability to accumulate charges of static electricity decreases by approximately 10-12 times.

It is known that the surface resistance of materials determines its ability to statically electrify (L. Loeb, 1963). Studies have shown that after short-term wetting and drying of samples in air for 15 minutes, their surface resistance decreases by 5-10 times, and after drying for 24 hours - 1.5-3 times. If these samples are subjected to repeated wetting, their dielectric properties are not restored even 10 days after the last wetting. This is probably explained by the fact that the samples contain substances that can adsorb moisture in large quantities (clay, talc, barite, lime flour). Wetting the samples leads to the absorption of moisture throughout the material. Desorption from the inner layers occurs much more slowly than from the surface layers.

Among the factors influencing the level of accumulation of static electricity on polymer materials, the load on the sample should also be noted. The amount of charge is directly proportional to the load. Increasing the load by 2 times leads to an increase in charge by 1.3-1.5 times.

The level of electrification of synthetic fabrics is significantly influenced by their conductivity and sorption properties. Materials with low conductivity and sorption properties have the greatest electrification properties (E. Kh. Tsirin, 1973).

There is a clear correlation between the electrification of fabrics and their sorption properties (Table 3).

Table Dependence of the electrification of textile materials on their sorption properties

In the warping shop, static electricity on the workers’ bodies is not registered, but on the equipment it is 1 kV. The values ​​of static electricity on the production line of a knitting factory are determined within approximately the same limits. Highest levels static electricity accumulates on a napping machine, in particular during the production of cotton products (up to 20-30 kV), half-woolen (up to 20 kV), silk with viscose (up to 30 kV), nylon (up to 40 kV).

The electrification of workers involved in various technological processes is: when working on a napping machine - from 0.5 to 2 kV (depending on the type of fabric), on a shearing machine - from 1.5 to 3 kV. No electrification is observed in the warp knitting shop or other areas.

A very important and urgent task is the development of measures that eliminate or reduce the possibility of exposure to static electricity on humans at work and at home. To reduce the electrification of dielectrics, several methods have been developed: ionization of the environment, installation of special devices - neutralizers, and increasing the conductivity of materials. Among them, the most effective is to increase the conductivity of polymers by introducing antistatic agents into their composition. These substances remove static charges that may accumulate on the surface of the material, so they must be hydrophilic or ionic in nature.

The use of antistatic drugs in production in our country is in its infancy. The results of the first experimental studies of polymer materials with antistatic agents introduced into their composition confirmed the promise of this method. Applying an antistatic agent to the surface reduces the electrification of the material by 2-5. once.

The antistatic properties of the drug and its quantity are of great importance. Among the 8 antistatic drugs studied (stearox-6, stearox-920, oxalin G-2, syntanol DT-7, syntanol DS-10, oxanol US-17, oxanol 0-18, drug OS-20), the most effective were oxanol 0- 18, oxalin C-2 and syntanol DS-10.

The basic requirements for antistatic agents are as follows. They must prevent the accumulation of static charges or discharge them very quickly. In addition, antistatic agents must increase the surface conductivity of plastics such that associated charges quickly drain into the surrounding atmosphere. An increase in surface conductivity can be achieved either by increasing the moisture concentration in the material by increasing the hygroscopicity of its surface or by creating organic conductive layers.

One of effective methods reducing the accumulation of static electricity is a decrease in the coefficient of friction between the polymer and the material in contact with it. To do this, it is necessary that the antistatic agent forms a rubber-like film on the surface of the plastic.

Currently, a huge number of substances have been proposed as antistatic agents. Most of them belong to one of 5 classes: nitro compounds (long chains of amines, amides and quaternary bases or salts), sulfonic acids or arylalkyl sulfonates, phosphorus-containing acids or arylalkyl phosphates, polyglycols and their derivatives, including polyglycol esters of fatty acids and polyglycolaryl alkyl derivatives, polyhydrolytic alcohols and their derivatives.

Antistatic agents are applied to the surface of plastics or incorporated into them. Antistatic additives introduced into the plastic composition are more effective. Materials used for these purposes must have low electrical resistance and form a film on the surface of low surface energy solutions of water or other volatile solvents.

The effectiveness of all antistatic agents decreases significantly with decreasing atmospheric humidity. This is probably due to the fact that small amounts of sorption moisture affect the ionization that can occur in non-ionic antistatic agents.

Many can form an antistatic surface chemical compounds. At the same time, the choice of introducing these substances into polymers is more limited, since their effectiveness may be specific to each type of plastic. For example, quaternary ammonium compounds are preferred for use in polystyrene, while polyethylene glycol ethers are preferred for use in polyethylene. In addition, these additives must have a certain set of properties. By chemical properties they must have a certain compatibility with plastics, since there are limits at which efficiency is greatest. Very high compatibility leads to complete dissolution of the agent in the plastic. Consequently, there must always be a certain amount of a substance on the surface of the material that imparts antistatic properties. If the surface layer is washed off, the antistatic agent remains in the mass of the material and does not rise to the surface. Very low compatibility leads to stratification of the mass. This can happen with a low molecular weight compound and lead to undesirable results such as sweating. Experiments and observations in vivo have shown that the agent should have average compatibility with plastics.

Compatibility is determined by the ability of the antistatic agent to diffuse through the material. This property is especially important and is an indicator of the effective life expectancy of the agent. Obviously, compounds with low molecular weight will move freely in the mass of the material to its surface. In such cases, although the agent's effectiveness may be good, its life will be short. The agent can be easily worn off by normal use, and since its quantity is limited, its activity cannot be prolonged. At the same time, compounds with high molecular weight or high compatibility will move more slowly and their activity will be longer. In addition, if the compatibility of the additive with the plastic is very high, then more antistatic agent is required, and therefore its mechanical properties deteriorate.

The rate of diffusion is determined by the time it takes for the maximum concentration to reach the surface, or the time between the production of the product and its antistatic properties. The equilibrium between compatibility and diffusion rate can be adjusted by two methods. First of all, the effect of the antistatic agent can be modified by adding a second component, thereby increasing or decreasing compatibility and subsequent movement. Another way would be to create an antistatic agent whose molecular structure includes chemical compounds that strike a balance between compatibility and transferability. For example, a series of alcohol quaternary ammonium compounds can be prepared with various cationic and anionic compounds.

Many antistatic agents are not used due to their thermal instability in the production and processing of plastics. Currently, there are few compounds with a stable chemical structure that can provide a permanent antistatic effect and at the same time withstand high temperature and pressure without breaking down. For example, it has been established that quaternary ammonium compounds are unstable at high temperature and in plastic processing

This reaction is dangerous not only because the added substance loses its antistatic properties, but also because acid is released, which increases corrosion of equipment used in the production of plastics.

Antistatic agents must be low volatile and non-toxic and have a long-lasting antistatic effect. It is very difficult to predict the duration of action of an antistatic agent, since during the operation of plastics, its surface layer, diffusion and equilibrium of the antistatic agent are constantly disturbed.

Antistatic additives added to plastic must be a certain percentage in relation to it. The optimal concentration of antistatic agents depends mainly on their affinity to the polymer and the surface area per unit volume, i.e. how much greater the surface area of ​​the particles per unit volume in the additive is than in the polymer. Observations have shown that a minimum concentration of compounds is required to form a durable surface layer. A further increase in concentration does not give an immediate effect, although it is possible that a reserve is formed to replenish losses of the compound during decay.

The agent must have a molecular weight low enough to migrate to the surface, yet high enough to have some resistance and not be easily removed from the surface. Antistatic agents should be colorless or lightly colored, since highly colored compounds cause certain difficulties in obtaining pale tones.

The action of antistatic agents must be based on one or more physical phenomena: hygroscopicity - collecting water from the atmosphere, polarity - the agent is a polar compound and conducts current, viscosity - the agent must have such a degree of viscosity that it captures electrons moving to the surface.

There cannot be universal anti-electrostatic agents, since they are determined by the type of plastic, its purpose, etc.

Recently, much attention has been paid to the study of the biological effects of static electricity. This interest is not accidental. It is known that static electricity, which occurs, for example, when wearing chlorine underwear, has a therapeutic effect (K. A. Rapoport, 1965) for some neurological diseases (rheumatism, radiculitis, plexitis, etc.). Probably, the same effect is observed here as with one of the methods of electrotherapy - franklinization. Franklinization refers to static electricity treatment, which involves the combined action of ionized air, a high-voltage field and small discharges between the body and the franklinizer electrodes. However, the widespread use of static electricity as remedy causes skepticism. This is explained by the fact that it has not yet been clarified which phenomena - physical or chemical - lead to improvement.

At the same time, it is known that ions not only determine the oxygen supply of the skin, but also activate metabolic processes in the cell. Therefore, when wearing clothes, it is very important what polarity the SEP will be on it. For example, when wearing clothes made of lavsan fabric around the body, an SEP of negative polarity appears, which does not allow air ions with a negative charge to pass through. When wearing clothes made of artificial wool, an electrostatic field with a positive charge is formed around the body, preventing the penetration of oxygen ions into the skin (N. N. Alfimov, V. V. Belousov, 1973).

Biochemical processes in the body are impossible without the exchange of electrical charges on the molecules of proteins, fats, carbohydrates and salts.

Impaired penetration of air ions can contribute to the development of trophic changes in the skin and, in a reflex way, to a number of other pathological changes in the body, especially in the cardiovascular and nervous systems.

It has been experimentally established that there is a close correlation between electrical; skin resistance with such indicators of the state of the central nervous system, as a latent reaction time to light, sound, heat, as well as the connection between the level of electrical resistance of the skin and the threshold of sensations arising from discharges of static electricity (N. S. Smirnitsky, G. A. Antropov, 1969). Individual skin sensitivity to the effects of static electricity is also noted. This is probably due to the different skin conditions in different people. Skin can be oily, normal or dry. The drier it is, the greater its electrical resistivity and, therefore, the more charges it retains. With age, the cells of the body, including the epidermis, undergo some changes, and the skin becomes drier. Elderly people more often complain of electrical charges when touching uncharged objects or another person (S. Yu. Morozov, 1969). The skin dries out and frequent washing hot water with soap.

In an acute experiment it was discovered (F.G. Portnov, 1968) that as a result of short-term (15-60 min) action of SEP 4000 V/cm, the number of red blood cells, the percentage of hemoglobin and the autonomic functions of the body (heart rate and respiration) deviate from the original level.

In a chronic experiment under the influence of SEP with a tension of 2000 f/cm for 1.5 months, 4 hours a day, 6 times a week, hematological parameters and condition cardiovascular systems s did not change statistically significantly. The chronic experiment showed a tendency to weaken the reactivity of the animal body in relation to the action of SEP.

In production conditions where the SEP reached 30-40 kV, diseases of the nervous and cardiovascular systems, disorders of the ovarian-menstrual cycle, influenza and catarrh of the upper respiratory tract. These data indicate that individuals exposed to long-term SEP have resistance to infectious diseases demoted.

In individuals exposed to static electricity, the skin's resistance to electric current, the strength and endurance of muscles and bones decreases, nervous reactions to light and sound slow down, and a higher number of days of disability is noted than in people who were not exposed to SEP (L. I. Maksimova, 1972). Under the influence of SEP, the pH of gastric juice is significantly reduced and blood clotting time is reduced.

When exposed to SEP with a voltage of 400-500 V/cm, experimental animals show substantial and conformational changes in the cells of the brain and spinal cord, adrenal glands, liver, kidneys, spleen, skeletal muscles, hematocrit decreases, thermal coagulation time of plasma proteins increases, eosinophilia (B. M. Medvedev, S. D. Kovtun, 1969). Electrophysiological studies of functional status peripheral nerves indicate that SES increases the latent period, the duration of the action potential and the absolute refractory phase of excitation. The authors consider an increase in these indicators over time as a slight decrease in the mobility of excitation processes in the nerve fibers of mixed peripheral nerves. This occurs due to disruption of cellular permeability to potassium and sodium ions, which, as is known, is directly related to changes in electrical reactions in cells.

It has been established that SEP with a voltage of 500 V/cm reduces tactile and pain sensitivity, reduces tone and reactivity vascular system skin, blood circulation in the skin, increases skin resistance, lowers the redox potential (M. G. Shandala, V. Ya. Akimenko, 1973). SEP with a voltage of 1000 V/cm, in addition to the indicated changes, reduces the level of functional stability of cold receptors, the bactericidal properties of the skin and the magnitude of galvanic skin reflexes, and increases the potentials in the active points of the heart and lungs. An SEP of 250 V/cm does not cause any biological changes, and therefore is recommended as a voltage for accumulation on clothing. As a RL for accumulation/SEP on clothing, K. A. Rapoport and co-authors (1973), based on a survey of subjects, recommend a voltage of 300 V/cm cm.

In order to regulate the SEP accumulated on polymer materials used in construction, we conducted studies on white rats under simulated conditions (K. I. Stankevich et al., 1972). The installation we created consists of a chamber measuring 45 X 30 X 13 cm. Using brackets, the electrodes can move closer and further from the camera, as well as change their position in relation to the camera (horizontally or vertically). This makes it possible to study the influence of the direction of field lines in relation to the body of experimental animals. In the chamber it is possible to study the biological effects of both the SEP and its charge.

Aerofranklinizers connected to the network are used as a generator of static electricity. To monitor the voltage supplied by the aero franklinizers, a kilovoltmeter is installed in the chamber. Calculation of the SEP tension (E) in the chamber is carried out according to the formula:

Where G is the voltage marked on the kilovoltmeter scale;

N is the distance between the electrodes.

We carried out studies under simulated conditions at SEP voltages of 1800, 1100, 300, 150 V/cm, i.e., under the most typical natural conditions. According to these studies, the most sensitive indicators of the effect of SEP on the animal body are redox enzymes - peroxidase, catalase, succinate dehydrogenase. At a field voltage of 300 V/cm and higher, peroxidase activity, peroxidase and catalase indices statistically significantly decreased in experimental animals, but these changes began only from the 2nd month of the experiment.

2 weeks after the start of the experiment, the content of adrenaline in the urine statistically significantly increased, blood clotting increased, and the osmotic resistance of erythrocytes decreased.

There was a stable decrease in the thermoresistance of plasma proteins and blood leukocytes, as well as an increase in the amount of sodium ions in the blood plasma. The latter is probably due to the increased permeability of cell membranes under the influence of SEP. And, as is known, Na+ ions affect the excitability of the nervous system, water balance and the formation of adaptive properties of the body. Blood parameters (number of red blood cells, eosinophils, reticulocytes, hemoglobin percentage, sugar content) were of a phase nature, which, apparently, can be explained by the irritating effect of SEP on the hematopoietic function of the bone marrow and the initial stress in the body with subsequent adaptation.

Along with animal studies, clinicians have conducted comprehensive examination service personnel of a long-distance telephone exchange, where the electrification of floor coverings based on PVC-linoleum and the body of workers reaches 10-30 kV. 71% of employees experienced functional disorders from the nervous system, and in 44% - from the cardiovascular system. Employees complained of constant headaches, increased irritability and fatigue, and pain in the heart area, which intensified during the working day. Hematological studies revealed severe leukopenia and a decrease in hematocrit.

Thus, studies have shown that the SEP value of 300 V/cm is threshold, and 150 V/cm is subthreshold and can be regulated as “inactive”.

A very important theoretical and practical issue of the problem under consideration is the elucidation of the mechanism of biological action of SEP. From the presented data it is clear that uncovering the mechanisms of responses to SES presents significant difficulties.

B. M. Medvedev and S. D. Kovtun (1969) believe that the mechanism of biological action of SEP is based on disturbances in conformational processes. protein cellular components as a consequence of shifts in electrostatic intracellular forces and disruption of cellular metabolism. F. G. Portnov and co-authors (1973) consider the participation of adrenergic receptors as one of the links in the mechanism of biological action of SEP.

Our studies indicate that the permeability of cell membranes and disruption of the activity of oxidoreductases play an important role in the mechanism of biological action of SEP.

Yu. L. Kholodov (1966) believes that the physiological influence of SEP on the body is carried out in a reflex way. By irritating the endings of the trigeminal and other nerves, SEP can cause a change in the functional state of the central nervous system. In addition, changes in skin sensitivity, stimulation of capillary circulation, normalization of vascular tone, a shift in the morphological composition of the blood, improvement of gas exchange and gastrointestinal tract activity are observed.

Static tension brings benefits and sometimes troubles. Let's try to figure out why. At a friendly party, mix a spoonful of salt and a pinch of pepper in a cup. Ask friends to separate the mixture into its components. After unsuccessful attempts, show them a small experiment. Comb your hair with a plastic comb and then touch the contents of the cup with it. The pepper particles will pop out of the container on their own. At the heart of this fun experiment is the interesting phenomenon of static electricity.

By the word “electricity,” scientists mean the interaction of electric charges. Their movement is ordered so that people can use a variety of devices and mechanisms: from a kettle to a trolleybus. Static electricity is in no hurry to start up a refrigerator or mobile phone. It is in a state of relaxation. That is, the free charge remains until conditions for movement arise. It's pretty simple: imagine a firefighter waiting for a call about a house fire.

How static electricity was discovered

About eight thousand years ago, our ancestors domesticated wild goats and sheep. They noticed that wool products had an unusual ability to accumulate charge. For the first time, the ancient Greek mathematician Thales tried to formulate the concept of static electricity. He used amber for his experiments. The stone attracts small, light particles when rubbed with a woolen cloth. Then they could not benefit from this phenomenon. Electron in Greek is amber. Much later, an elementary particle with a negative charge was named after him.

Two thousand years later, the court physician to the Queen of England, William Gilbert, describes what static electricity is. In his scientific work in physics, he emphasizes the related nature of electricity and the phenomena of magnetism. The Briton's research became the beginning for a detailed study of the topic among colleagues in Europe. A clearer concept of static electricity was given by the experience of Otto von Guericke. A German assembled the first electrostatic mechanism. It was a ball of sulfur on an iron rod. As a result, the scientist learned that objects under the influence of electricity can not only attract, but also repel each other.

A little science

Today, the causes of static electricity are well studied. This phenomenon is observed on the surfaces of some objects as a result of interaction with other materials. The strength of the charge and its ability to persist depend on their properties and composition. The simplest example of interaction between bodies is friction. The more intensely and quickly the girl combs her hair, the stronger the charge is formed. Static electricity surrounds people everywhere, but they don't always notice it. Electrostatic charges are formed in sunny weather when driving a car. They accumulate from the tension that occurs between the asphalt and the body. If the driver does not use an antistatic agent, it will cause a spark.

Danger of static electricity

Most static electricity phenomena in Everyday life people just don't notice. Minor problems may arise when using wool or synthetic clothing. The magnitude of the currents in this case is very small and does not leave injuries. At the household level it is quite safe. Difficulties arise when it comes to industrial production, processing enterprises or mechanical engineering. Electrostatic charges are present in large quantities in production. Machine tools, separators, and conveyor belts can have significant potential.

If there are many such factors, an electric field with high intensity values ​​is formed. Being in this environment is not only uncomfortable, but also dangerous to your health. The main cause of concern in hazardous work environments is the fire hazard of static voltage. Large charges can accumulate on the surface of equipment or clothing. We are talking about working with flammable liquids, flammable gases and explosive mixtures. A spark can cause a serious accident.

Anti-static electricity

To avoid the adverse effects of this phenomenon, a state standard for the indicator of electrostatic field strength has been developed. Its maximum permissible level 60 kV/m per hour. They may vary depending on the time the worker is in the hazardous area. Measuring the level of static electricity charge is a task for a professional. The key indicator is the dependence of the field resistance (its ability to prevent the passage of current) and its intensity (the ratio of the field strength to the amount of charge). The operation of measuring instruments is based on this.

The effect of static electricity on the human body can be destructive and causes various diseases, including mental ones. If we talk about industrial safety in general, there are two main ways to combat it:

1. Reduces the possibility of electrostatic charges forming.
2. Eliminates the accumulation of electrostatic charges.

To reduce friction, equipment parts are ground and lubricated. The same materials are used to make the mechanisms. You can get rid of charges by grounding the machines.

Static electricity can be harmful when spraying or splashing liquids from low performance current conductivity. This risks igniting them.

The problem is solved by using special containers and processing conditions. TO individual means protection against static voltage can be classified under several names:

1. Special clothing (pants and jacket).
2. Shoes with insulating soles.
3. Gloves.
4. Bracelets for dielectric stress relief.

Every cloud has a silver lining

Static electricity brings not only harm, but also benefit. With the development of technology, people have tamed static voltage and learned to benefit from it. This phenomenon is successfully used in the lamination of lumber and in the paper industry. The accumulated charge helps in the production and application of labels and in high-quality powder painting of cars.

The daily activity of any person is connected with his movement in space. At the same time, he not only walks, but also travels by transport.

During any movement, a redistribution of static charges occurs, changing the balance of internal equilibrium between the atoms and electrons of each substance. It is associated with the process of electrification, the formation of static electricity.

U solids The distribution of charges occurs due to the movement of electrons, and in liquids and gases - both electrons and charged ions. All of them together create a potential difference.

Reasons for the formation of static electricity

The most common examples of the manifestation of static forces are explained in school during the first physics lessons, when they rub glass and ebonite rods on woolen fabric and demonstrate the attraction of small pieces of paper to them.

There is also known experience in deflecting a thin stream of water under the influence of static charges concentrated on an ebonite rod.

In everyday life, static electricity manifests itself most often:

when wearing woolen or synthetic clothing;

walking in shoes with rubber soles or woolen socks on carpets and linoleum;

using plastic items.

The situation is aggravated by:

dry indoor air;

reinforced concrete walls from which multi-storey buildings are made.

How is a static charge created?

Usually physical body contains an equal number of positive and negative particles, due to which a balance is created in it, ensuring its neutral state. When it is violated, the body acquires an electrical charge of a certain sign.

Static means a state of rest when the body does not move. Polarization can occur inside its substance - the movement of charges from one part to another or their transfer from a nearby object.

Electrification of substances occurs due to the acquisition, removal or separation of charges when:

interaction of materials due to friction or rotation forces;

sudden temperature change;

irradiation different ways;

dividing or cutting physical bodies.

They are distributed over the surface of an object or at a distance from it of several interatomic distances. For ungrounded bodies they spread over the area of ​​the contact layer, and for those connected to the ground loop they flow onto it.

The acquisition of static charges by the body and their drainage occur simultaneously. Electrification is ensured when the body receives a greater energy potential than it expends into the external environment.

A practical conclusion follows from this provision: to protect the body from static electricity, it is necessary to remove the acquired charges from it to the ground circuit.

Methods for assessing static electricity

Physical substances, based on their ability to form electrical charges of different signs when interacting with other bodies by friction, are characterized on the scale of the triboelectric effect. Some of them are shown in the picture.

The following facts can be cited as an example of their interaction:

walking in wool socks or shoes with rubber soles on a dry carpet can charge the human body up to 5÷-6 kV;

the body of a car driving on a dry road acquires a potential of up to 10 kV;

the drive belt rotating the pulley is charged up to 25 kV.

As we can see, the potential of static electricity reaches very high values ​​even in domestic conditions. But it does not cause us much harm because it does not have high power, and its discharge passes through the high resistance of the contact pads and is measured in fractions of a milliamp or a little more.

In addition, it is significantly reduced by air humidity. Its effect on the amount of body stress upon contact with various materials is shown in the graph.

From his analysis, the conclusion follows: in a humid environment, static electricity appears less. Therefore, various air humidifiers are used to combat it.

In nature, static electricity can reach enormous values. When clouds move over long distances, significant potentials accumulate between them, which manifest themselves as lightning, the energy of which is enough to split a century-old tree along the trunk or burn down a residential building.

When static electricity is discharged in everyday life, we feel “tingling” in our fingers, see sparks emanating from woolen items, and feel a decrease in vigor and efficiency. The current to which our body is exposed in everyday life has a negative effect on well-being and the state of the nervous system, but it does not cause obvious, visible damage.

Manufacturers of measuring industrial equipment produce devices that allow you to accurately determine the voltage of accumulated static charges both on equipment housings and on the human body.

How to protect yourself from static electricity at home

Each of us must understand the processes that create static discharges that pose a threat to our body. They should be known and limited. For this purpose, various educational events are held, including popular television programs for the population.

On them available means shows ways to create static voltage, principles of its measurement and methods of performing preventive measures.

For example, given the triboelectric effect, it is best to use natural wood combs for combing your hair, rather than metal or plastic, as most people do. Wood has neutral properties and does not form charges when rubbed against hair.

To remove static potential from the car body when driving on a dry road, use special antistatic tapes attached to the bottom. Various types of them are widely available on sale.

If there is no such protection on the car, then the voltage potential can be removed by briefly grounding the body through a metal object, for example, a car ignition key. It is especially important to perform this procedure before refueling.

When a static charge accumulates on clothing made of synthetic materials, it can be removed by treating the vapors from a special canister containing “Antistatic” composition. In general, it is better to use such fabrics less and wear natural materials made from linen or cotton.

Shoes with rubberized soles also contribute to the accumulation of charges. It is enough to put antistatic insoles made of natural materials into it, and the harmful effects on the body will be reduced.

The influence of dry air, characteristic of city apartments in winter, has already been discussed. Special humidifiers or even small pieces of dampened cloth placed on the battery improve the situation and reduce the formation of static electricity. But regular wet cleaning of premises allows you to promptly remove electrified particles and dust. This is one of the best ways to protect yourself.

Household electrical appliances also accumulate static charges on their bodies during operation. A potential equalization system connected to the general grounding loop of the building is designed to reduce their impact. Even a simple acrylic bathtub or an old cast-iron structure with the same insert is susceptible to static and requires protection in a similar way.

How to protect against static electricity in production

Factors that reduce the performance of electronic equipment

Discharges that occur during the manufacture of semiconductor materials can cause great harm, disrupt the electrical characteristics of devices, or even disable them.

In production conditions, the discharge can be random and depend on a number of different factors:

the size of the formed capacity;

energy potential;

electrical resistance of contacts;

type of transient processes;

other accidents.

In this case, at the initial moment of about ten nanoseconds, the discharge current increases to a maximum, and then it decreases within 100÷300 ns.

The nature of the occurrence of a static discharge on a semiconductor device through the operator’s body is shown in the picture.

The magnitude of the current is influenced by: the charge capacity accumulated by a person, the resistance of his body and contact pads.

During the production of electrical equipment, a static discharge can be created without operator participation due to the formation of contacts through grounded surfaces.

In this case, the discharge current is affected by the charge capacity accumulated by the device body and the resistance of the formed contact pads. In this case, the semiconductor is initially simultaneously affected by the induced high voltage potential and the discharge current.

Due to this complex impact damage may be:

1. obvious, when the performance of the elements is reduced to such an extent that they become unsuitable for use;

2. hidden - due to a reduction in output parameters, sometimes even falling within the established factory characteristics.

The second type of malfunction is difficult to detect: they most often result in loss of performance during operation.

An example of such damage from the action of high static voltage is demonstrated by graphs of the deviation of the current-voltage characteristics in relation to the KD522D diode and the integrated circuit BIS KR1005VI1.

The brown line numbered 1 shows the parameters of semiconductor devices before testing with increased voltage, and curves numbered 2 and 3 show their decrease under the influence of an increased induced potential. In case #3 it has a greater impact.

Damage may be caused by:

excessive induced voltage, which breaks through the dielectric layer of semiconductor devices or disrupts the structure of the crystal;

high density of flowing current, causing high temperatures, leading to melting of materials and burning of the oxide layer;

tests, electrical and thermal training.

Hidden damage may not affect performance immediately, but after several months or even years of operation.

Methods for implementing protection against static electricity in production

Depending on the type of industrial equipment, one of the following methods of maintaining operability or a combination of them is used:

1. eliminating the formation of electrostatic charges;

2. blocking their entry into the workplace;

3. increasing the resistance of devices and components to the action of discharges.

Methods No. 1 and No. 2 allow you to protect a large group of different devices in a complex, and No. 3 is used for individual devices.

High efficiency in maintaining the operability of the equipment is achieved by placing it inside a Faraday cage - a space fenced on all sides with a fine-mesh metal mesh connected to a ground loop. External electric fields do not penetrate inside it, but static magnetic fields are present.

Cables with a shielded sheath work on this principle.

Static protection is classified according to the principles of execution into:

physical and mechanical;

chemical;

structural and technological.

The first two methods allow you to prevent or reduce the formation of static charges and increase the rate of their drainage. The third technique protects devices from the effects of charges, but it does not affect their drainage.

The drainage of discharges can be improved by:

creation of coronation;

increasing the conductivity of materials on which charges accumulate.

These issues are resolved:

air ionization;

increasing working surfaces;

selection of materials with better volumetric conductivity.

Due to their implementation, lines prepared in advance are created to drain static charges onto the ground loop, preventing them from reaching the working elements of devices. It is taken into account that the total electrical resistance of the created path should not exceed 10 Ohms.

If materials have high resistance, then protection is performed in other ways. Otherwise, charges begin to accumulate on the surface, which can be discharged upon contact with the ground.

An example of complex electrostatic protection of a workplace for an operator involved in the maintenance and adjustment of electronic devices is shown in the picture.

The table surface is connected to the ground loop through a connecting conductor and a conductive mat using special terminals. The operator works in special clothing, wears shoes with conductive soles and sits on a chair with a special seat. All these measures make it possible to efficiently discharge accumulated charges to the ground.

Working air ionizers regulate humidity and reduce the potential of static electricity. When using them, it is taken into account that the increased content of water vapor in the air negatively affects human health. Therefore, they try to maintain it at a level of about 40%.

Also effective way There may be regular ventilation of the room or the use of a ventilation system in it, when the air passes through filters, is ionized and mixed, thus ensuring the neutralization of emerging charges.

To reduce the potential accumulated by the human body, bracelets can be used to complement a set of antistatic clothing and shoes. They consist of a conductive strip that is attached to the arm using a buckle. The latter is connected to the ground wire.

With this method, the current flowing through human body. Its value should not exceed one milliamp. Larger values ​​may cause pain and electrical injuries.

As the charge flows to the ground, it is important to ensure that it leaves at a rate of one second. For this purpose, floor coverings with low electrical resistance are used.

When working with semiconductor boards and electronic components, protection against damage by static electricity is also provided by:

forced shunting of the terminals of electronic boards and units during checks;

using tools and soldering irons with grounded working heads.

Containers with flammable liquids located on vehicles are grounded using a metal circuit. Even the fuselage of the aircraft is equipped with metal cables, which act as protection against static electricity during landing.

What is static electricity

Static electricity occurs when intraatomic or intramolecular equilibrium is disturbed due to the gain or loss of an electron. Typically, an atom is in equilibrium due to the same number of positive and negative particles - protons and electrons. Electrons can easily move from one atom to another. In doing so, they form positive (where there is no electron) or negative (a single electron or an atom with an extra electron) ions. When this imbalance occurs, static electricity occurs.

The electric charge of an electron is (-) 1.6 x 10 -19 coulombs. A proton with the same charge has positive polarity. The static charge in coulombs is directly proportional to the excess or deficiency of electrons, i.e. number of unstable ions.

A coulomb is a basic unit of static charge that determines the amount of electricity passing through cross section conductor in 1 second at a current of 1 ampere.

A positive ion is missing one electron, hence it can easily accept an electron from a negatively charged particle. A negative ion, in turn, can be either a single electron or an atom/molecule with a large number of electrons. In both cases, there is an electron that can neutralize the positive charge.

How is static electricity generated?

The main causes of static electricity:

• Contact between two materials and their separation from each other (including friction, winding/unwinding, etc.).

• Rapid temperature change (for example, when the material is placed in the oven).

• High energy radiation, ultraviolet radiation, X-rays, strong electric fields (unusual for industrial production).

• Cutting operations (for example, on saws or paper cutting machines).

• Induction (the generation of an electric field caused by a static charge).

Surface contact and material separation are perhaps the most common causes of static electricity in roll film and sheet plastic processing applications. Static charge is generated during the process of unwinding/winding materials or moving different layers of materials relative to each other.

This process is not entirely clear, but the most truthful explanation for the appearance of static electricity in this case can be obtained by drawing an analogy with a flat-plate capacitor, in which mechanical energy is converted into electrical energy when the plates separate:

Resultant stress = initial stress x (final plate spacing/initial plate spacing).

When the synthetic film touches the feed/take-up shaft, the low charge flowing from the material to the shaft causes an imbalance. As the material passes the contact zone with the shaft, the stress increases in the same way as in the case of capacitor plates at the moment of their separation.

Practice shows that the amplitude of the resulting voltage is limited due to electrical breakdown that occurs in the gap between adjacent materials, surface conductivity and other factors. When the film exits the contact zone, you can often hear a faint crackling sound or observe sparking. This occurs at the moment when the static charge reaches a value sufficient to breakdown the surrounding air.

Before contact with the shaft, the synthetic film is electrically neutral, but during the process of movement and contact with the feed surfaces, a flow of electrons is directed towards the film and charges it with a negative charge. If the shaft is metal and grounded, its positive charge drains quickly.

Most equipment has many shafts, so the amount of charge and its polarity can change frequently. The best way Static charge control is its precise determination in the area immediately in front of the problem area. If the charge is neutralized too early, it may recover before the film reaches this problem area.

Charge polarity

Static charge can be either positive or negative. For arresters direct current(AC) and passive dischargers (brushes), the polarity of the charge is usually not important.

Static Electricity Problems

Static discharge in electronics

It is necessary to pay attention to this problem, because... it often occurs during handling of electronic units and components used in modern control and measuring devices.

In electronics, the main danger associated with static charge comes from the person carrying the charge and cannot be ignored. The discharge current generates heat, which leads to the destruction of connections, interruption of contacts and rupture of microcircuit tracks. High voltage also destroys the thin oxide film on field-effect transistors and other coated elements.

Often components do not completely fail, which can be considered even more dangerous because... The malfunction does not appear immediately, but at an unpredictable moment during the operation of the device.

As a general rule, when working with static-sensitive parts and devices, measures should always be taken to neutralize the charge accumulated on the human body.

Electrostatic attraction/repulsion

This is perhaps the most widespread problem encountered in plants involved in the production and processing of plastics, paper, textiles and related industries. It manifests itself in the fact that materials independently change their behavior - they stick together or, conversely, repel each other, stick to equipment, attract dust, wrap incorrectly around the receiving device, etc.

Attraction/repulsion occurs in accordance with Coulomb's law, which is based on the principle of square opposition. In simple form it is expressed as follows:

Force of attraction or repulsion (in Newtons) = Charge (A) x Charge (B) / (Distance between objects 2 (in meters)).

Consequently, the intensity of this effect is directly related to the amplitude of the static charge and the distance between attracting or repulsive objects. Attraction and repulsion occur in the direction of the electric field lines.

If two charges have the same polarity, they repel, if they have the opposite polarity, they attract. If one of the objects is charged, it will provoke an attraction, creating a mirror copy of the charge on neutral objects.

Fire risk

The risk of fire is not a common problem for all industries. But the likelihood of fire is very high in printing and other enterprises where flammable solvents are used.

In hazardous areas, the most common sources of fire are ungrounded equipment and moving conductors. If the operator is wearing athletic or non-conductive shoes while in a hazardous area, there is a risk that his body will generate a charge that could cause solvents to ignite. Ungrounded conductive machine parts also pose a hazard. Everything located in the hazardous area must be well grounded.

The following information provides a brief explanation of the fire-causing potential of static discharge in flammable environments. It is important that inexperienced salespeople be aware of the types of equipment in advance to avoid mistakes in selecting devices for use in such conditions.

The ability of a discharge to provoke a fire depends on many variable factors:

• discharge type;

• discharge power;

• discharge source;

• discharge energy;

• the presence of a flammable environment (solvents in the gas phase, dust or flammable liquids);

• minimum ignition energy (MEI) of a flammable environment.

Types of discharge

There are three main types - spark, brush and sliding brush discharges. Corona discharge in this case is not taken into account, because it has low energy and occurs quite slowly. Corona discharge is most often harmless and should only be considered in areas of very high fire and explosion hazard.

Spark discharge

It generally comes from a moderately conductive, electrically insulated object. It could be a human body, a machine part, or a tool. It is assumed that all the energy of the charge is dissipated at the moment of sparking. If the energy is higher than the MEV of the solvent vapor, ignition may occur.

The spark energy is calculated as follows: E (in Joules) = ½ C U2.

Wrist discharge

Brush discharge occurs when sharp parts of equipment concentrate charge on the surfaces of dielectric materials, the insulating properties of which lead to its accumulation. A brush discharge has lower energy compared to a spark discharge and, accordingly, poses less of a ignition hazard.

Sliding brush discharge

A sliding brush discharge occurs on sheet or roll synthetic materials with high resistivity, having an increased charge density and different polarity of charges on each side of the sheet. This phenomenon can be caused by friction or spraying of the powder coating. The effect is comparable to the discharge of a parallel-plate capacitor and can be as dangerous as a spark discharge.

Discharge source and energy

The magnitude and geometry of the charge distribution are important factors. The larger the volume of a body, the more energy it contains. Sharp angles increase field strength and support discharges.

Discharge power

If an object having energy is not a very good conductor, such as the human body, the resistance of the object will weaken the discharge and reduce the danger. For the human body, a rule of thumb is to assume that any solvents with an internal minimum ignition energy of less than 100 mJ can ignite, even though the energy contained in the body may be 2 to 3 times higher.

Minimum ignition energy MEV

The minimum ignition energy of solvents and their concentration in the hazardous area are very important factors. If the minimum ignition energy is lower than the discharge energy, there is a risk of fire.

Electrocution

The issue of static shock risk in industrial environments is receiving increasing attention. This is due to a significant increase in occupational hygiene and safety requirements.

Electrocution caused by static electricity is, in principle, not particularly dangerous. It is simply unpleasant and often causes a strong reaction.

There are two common reasons static shock:

Induced charge

If a person is in an electric field and holds onto a charged object, such as a film spool, it is possible that their body will become charged.

The charge remains in the operator's body if he is wearing shoes with insulating soles until he touches grounded equipment. The charge flows to the ground and strikes a person. This also happens when the operator touches charged objects or materials - due to insulating shoes, the charge accumulates in the body. When the operator touches metal parts of the equipment, the charge can leak and cause an electrical shock.

When people walk on synthetic carpeting, a static charge is generated when there is contact between the carpet and the shoes. The electric shocks that drivers receive when leaving their car are provoked by the charge that arises between the seat and their clothing at the time of lifting. The solution to this problem is to touch a metal part of the car, such as a door frame, before rising from the seat. This allows the charge to flow safely to the ground through the vehicle's body and tires.

Electrical damage caused by equipment

Such an electric shock is possible, although it occurs much less frequently than damage caused by the material.

If the winding reel has a significant charge, it happens that the operator's fingers concentrate the charge to such an extent that it reaches the point of breakdown and a discharge occurs. In addition, if a metallic, ungrounded object is placed in an electric field, it can become charged by an induced charge. Because a metal object is conductive, the moving charge will discharge into a person who touches the object.

Static electricity is a set of phenomena associated with the emergence, conservation and relaxation of a free electric charge on the surface and in the volume of dielectric and semiconductor substances, product materials or on insulated conductors. Charges accumulate on equipment and materials, and accompanying electrical discharges can cause fires and explosions, disruption of technological processes, and the accuracy of readings of electrical devices and automation equipment.
Enterprises pose a particular danger due to the accumulation of static electricity. food production, in which technological processes are associated with crushing, grinding and sifting of the product (baking, confectionery, starch, sugar, etc.), with cleaning and processing of grain, transportation of solid and liquid products using conveyors and pipes (bulk storage warehouses for flour, brewing , distilleries, etc.).
When bodies that differ in temperature, concentration of charged particles, energy state of atoms, surface roughness and other parameters come into contact, a redistribution of electrical charges occurs between them. In this case, at the interface between the bodies, positive charges are concentrated on one of them, and negative charges on the other. An electrical double layer is formed. In the process of separating the contacting surfaces, some of the charges are neutralized, and some are retained on the bodies.
In production conditions, the electrification of various substances depends on many factors, and above all on physical and chemical properties processed substances, type and nature of the technological process. The magnitude of the electrostatic charge depends on the electrical conductivity of the materials, their relative dielectric constant, the speed of movement, the nature of the contact between the contacting materials, the electrical properties of the environment, relative humidity and air temperature. The electrification of dielectric materials increases especially sharply at a specific electrical resistance of 109 Ohm-m, as well as at a relative air humidity of less than 50%. With a resistivity of 108 Ohm-m or less, electrification is practically undetectable. The degree of electrification of liquids mainly depends on its dielectric properties and kinematic viscosity, flow speed, diameter and length of the pipeline, pipeline material, the condition of its internal walls, and liquid temperature. The intensity of charge formation is observed during filtration due to the large area of ​​contact of the liquid with the filter elements. Splashing of liquids when filling tanks with a free-falling stream of flammable liquid, for example in distilleries, is accompanied by electrification of the droplets, as a result of which there is a danger of electric charge and ignition of the vapors of these liquids. Therefore, pouring liquid into containers using a free-falling stream is not allowed. The distance from the end of the loading pipe to the bottom of the vessel should not exceed 200 mm, and if this is not possible, the jet is directed along the wall.
Heli, the electrostatic field strength above the surface of the dielectric reaches a critical (breakdown) value, and an electric discharge occurs. For air, the breakdown voltage is approximately 30 kV/cm.
Electrostatic spark safety is a condition in which the possibility of an explosion or fire from static electricity is excluded. Safe spark energy (in J) is determined by the formula:

Wi=kb*Wmin

Where kb is the safety factor used equal to 0.4-0.5; Wmin is the minimum energy that can cause ignition of the combustible mixture in question.
The maximum permissible charge value is taken to be such a value at which the maximum possible discharge energy W from the surface of a given substance does not exceed 0.4-0.5 of the minimum ignition energy of the environment Wmin.
The discharge (spark) energy of a dielectric (in J) can be determined by the formula:

W=0.5*C*V 2

Where C is the electrical capacitance discharged by the spark, F; V is the potential difference relative to the ground, V.
The minimum ignition energy of gas and steam-air mixtures is fractions of a millijoule.
The potential difference on the equipment can reach several thousand volts, and, as follows from the formula, even with an insignificant electrical capacitance carrying an electrostatic charge, the spark discharge energy can exceed the minimum ignition energy of an explosive atmosphere. For example, when transporting bulk materials on a conveyor with a rubber belt, the potential relative to ground can reach 45,000 V, and a leather drive belt with a speed of 15 m/s can reach up to 80,000 V.
Electrostatic charges, sufficient to ignite almost all explosive mixtures of air with gases, vapors and some dusts, can accumulate on a person (clothing made of synthetic fabrics, walking on dielectrics, using electrically non-conducting shoes, etc.), and also transfer to him from an electrified equipment and materials.
The potential of an electrostatic charge on a person can reach 15,000-20,000 V. Discharges of such potential do not pose a danger to humans, since the current strength is negligible and is felt like a prick, jolt, or cramp. However, under their influence, reflexive movements are possible, which can lead to a fall from a height, ending up in a dangerous zone of a machine, etc.
The discharge energy at a potential of 10,000 V and a human capacitance varying from 100 to 350 pF is 5–17.5 mJ. i.e. exceeds the minimum ignition energy values ethyl alcohol, benzene and carbon disulfide (0.95; 0.2; 0.0009 mJ, respectively).
Measures to protect against static electricity are divided into three main groups:

• preventing the possibility of electrostatic charge;
• reducing the electrostatic charge potential to a safe level;
• neutralizing charges of static electricity.

The main way to prevent the occurrence of electrostatic charge is to constantly remove static electricity from process equipment using grounding. Each system of apparatus and pipelines is grounded in at least two places. Rubber hoses are wrapped around grounded copper wire with a pitch of 10 cm. It should be borne in mind that, unlike electrical engineering, where materials with a resistivity measured in fractions of an Ohm are considered good conductors, in electrostatics the boundary between a conductor and a non-conductor is considered to be a resistivity value of 10 kOhm*m. Therefore, the maximum permissible resistance of a grounding device used only to remove electrostatic charge should not exceed 100 Ohms.
To prevent the formation of static electricity on elements of metal structures, pipelines for various purposes, located at a distance of less than 10 cm parallel to each other, closed circuits are used, created using metal grounded jumpers installed between them every 20 m or less.
To reduce the potential of electrostatic charge formed on equipment and processed materials to a safe level, technological methods are used (safe speeds of movement of transported liquid and dusty substances, selection of friction surfaces, materials for mutually compensating emerging charges, etc.), as well as methods of removal by increasing the relative humidity of the air and material, chemical surface treatment, applying antistatic substances and electrically conductive films. General or local air humidification of more than 70% ensures constant removal of electrostatic charges. The surface conductivity of materials is increased by treatment with surfactants, the use of coatings made of electrically conductive enamels, and lubricants. Charges of static electricity are neutralized using air ionization, in which the number of ion pairs formed per unit volume corresponds to the rate of occurrence of neutralized electrostatic charges. For this purpose, induction, radioisotope and combined ionizers are used.
To continuously remove electrostatic charges from a person, electrically conductive floors, grounded areas or work platforms, equipment, ladders, as well as personal protective equipment in the form of anti-electrostatic gowns and shoes with leather soles or conductive rubber soles are used.