Abstract on the subject "Life safety" Isaeva A.Yu.

Moscow Regional Social and Economic Institute

Vidnoe - 2002

1. The impact of electric current on the human body.

Lesions occur as a result of the action of technical or atmospheric electric current. The inept use of electrical devices, both in technology and in everyday life, as well as the malfunction of these devices, lead to electrical injuries. Mortality from defeat electric shock accounts for 9-10% of all cases, which is 10-15 times higher than mortality from other injuries.

Electrical injuries occur more often in the spring, summer and autumn, when the sweating of the skin increases, and there is also the possibility of being struck by lightning during a thunderstorm, when there is a significant accumulation of electrical charges in the atmosphere. In this case, the path of the lightning to the ground can be, as it were, “oriented” by a tree standing in the field, by a taller tree in the forest, or by any metal structure. Therefore, it is unsafe to be under them in a thunderstorm. To avoid the damaging effects of lightning in the room, you need to close windows, vents, disconnect all electrical appliances from the network.

For classification purposes, a boundary should be drawn at approximately 1000 volts, separating low-voltage and high-voltage faults. Low-voltage damage - burns with a limited surface of the lesion caused by a volt arc or flash. High voltage injuries (greater than 1000 volts) also arise from an arc or flash, but also cause large, destructive damage of a conductive type that can result in tissue death far from the point of contact.

Electrical damage is best explained in terms of the conversion of electrical energy into heat, which then leads to direct tissue destruction. In addition, the current high voltage has a direct destructive effect on cells. The relationship between voltage, resistance and current is described in the well-known Ohm's law:

I - equal to the current in amperes,

E - voltage in volts,

R is the resistance in ohms.

At high voltages, current flows through the tissues of the body and from the source (wound at the entrance) to the ground (wound at the exit). The body is a conductor of the current volume with the most pronounced tissue damage in places of high density and high values ​​in amperes. Hence, the limbs suffer the most from damage than the trunk and the points of entry and exit of voltage. The wound at the entrance has a skin surface, the tissues are tense due to coagulation and necrosis. The wound at the exit is usually larger, because the current must escape from the body, leaving big hole... There is the possibility of multiple electrical conduits within the body, resulting in multiple exits, thus exposing any organ or structure to the risk of electrical shock.

Arcuate lesions are usually accompanied by high frequency lesions. Arcuate lesions are best understood by imagining the destruction of tissue from the release of ionized particles between the poles of different electrical charges. Arcs occur when current travels from the body to the ground or from one part of the body to another, such as from the arm to the chest wall. When the arc has formed, there is sharp drop in voltage, but if the current source is active, the arc continues between the two poles. The distance the arc can travel increases by 2-3 cm for every 10,000 volts. The arc temperature can rise up to 20,000 C and usually results in a small, latent lesion that is deeply damaging. The greatest damage usually occurs deep in the limbs and is believed to be due to the close proximity to the bone that has the highest resistance.

Electrical damage is compounded by the “no release” phenomenon due to tetanic muscle contractility in contact with the changing current. When in contact with a high-voltage wire, the flexor muscles of the forearm undergo increased contracture, which makes it impossible to pull away from the source from here, the name "no release". Such contractures lead to a low-frequency current flow above the painful stimulus, but below it is required to cause tetany of the respiratory muscles. The patient avoids a difficult situation if only he is unconscious and falls to the side of the current source.

Deep conductive electrical injuries are characterized by deep massive muscle breakdown and deep edema under healthy skin. In addition, deep conductive lesions can affect remote areas of the central nervous system and the cavity of the chest and abdomen. Current entry and exit wounds are hallmarks of deep conductive damage.

Arcuate lesions produce localized, very deep areas of coagulation injury such as the wrist, elbow, perineum, and axillary region.

Superficial thermal burns occur with electrical injuries due to the flash or fire of clothing, affecting large areas of the body and thereby complicating the patient's metabolic trauma. Such burns can affect the proximal parts of the limbs, requiring subsequent amputation, forming unstable scars at the site of future prostheses.

Collateral damage occurs when a person is thrown from a power source or falls from a height. Possible concomitant injuries: intracranial trauma, spinal injuries, fractures of long bones, chest and intra-abdominal parenchymal injuries. The general effect of tissue from electrical influences in each organ system translates into specific, clinical damage: some of them are considered acute and life-threatening, others can have a gradual effect months and years after the accident. The following is a list of both acute and late effects of high voltage damage.

Heart failure.

Ventricular fibrillation.

Violation of the rhythm.

Coronary artery injury with or without myocardial infarction.

Direct damage to the myocardium.

Secondary acute renal failure.

Extensive damage to the central nervous system.

Unconsciousness, convulsions and coma.

Late hemiplegia or brain stem syndrome.

Spine

Vasomotor instability.

Dystrophy of sympathetic reflexes.

Abdominal wall rupture and evisceration.

Undynamic ileus and stomach atony.

Gastric or pancreatic ulcers.

Late visceral perforation.

Pancreatitis and electrical diabetes.

Direct liver damage and coagulopathy.

Rapid loss of potassium.

Stop breathing.

Direct damage to the chest wall.

Pleural injury and hydrothorax.

Lobar pulmonitis.

Bronchial perforation.

Pneumothorax with or without rib fracture.

Direct damage to the eyeball.

Rejection of the corneal or optic nerve.

Cataract.

Light maculopathy.

Direct damage.

Late rupture of blood vessels.

Internal damage.

Damage to the nutrient structures of the arteries and muscles.

Intrauterine death.

Spontaneous abortion.

Acute bone marrow suppression.

There are four degrees of electrical injury:

1 degree - the victim has a convulsive muscle contraction without loss of consciousness;

2 degree - convulsive muscle contraction in the patient is accompanied by loss of consciousness;

3 degree - the victim has not only loss of consciousness, but also a violation of cardiac activity and breathing;

4 degree - the patient is in a state of clinical death.

The clinical picture of electric shock consists of general and local symptoms. The subjective sensations of the victim when an electric current passes through him are varied: a slight jolt, burning pain, convulsive muscle contractions, tremors, etc. Signs: pallor of the skin, cyanosis, increased saliva production, there may be vomiting; pains in the area of ​​the heart and muscles of varying strength, unstable. After eliminating the effect of the current, the victim feels fatigue, weakness, heaviness in the whole body, depression or excitement. Loss of consciousness is observed in 80% of victims. Patients in an unconscious state are sharply agitated, restless. They have a rapid pulse, possibly involuntary urination.

With an electrical injury that caused convulsive muscle contractions or a fall from a height, various bone fractures and joint dislocations may occur. In case of electrical injury with extensive burns, the damage to the internal organs, as a rule, is much less pronounced. This is due to the fact that charred and burnt tissues create, as it were, an obstacle to the penetration of current beyond the burn. Electrical burns of a small area immediately after exposure to the current have clear boundaries; there is a lighter rim around the dead black tissue. Swelling of the surrounding tissues develops very quickly. As a rule, there is no pain in the area of ​​electric burn.

2. First aid for electric shock.

First aid in all cases should begin with the immediate release of the victim from further contact with the electric current circuit. The most in a simple way is the disconnection of the circuit with a switch or breaker, unscrewing the "plug", etc. But if they are far away or for some other reason it is impossible to turn them off, then the current-carrying wire should be cut off or cut, and the wire should be taken away from the victim. Care must be taken so that the rescuer does not become part of the electrical circuit - when cutting the wire, you need to wrap the handle of the tool with a dry woolen, silk or rubberized cloth, if it is not made of dry insulator. Cut the wires separately to avoid short circuits. When de-energizing the victim, the caregiver should stand on any dry rubber, wood, glass or other object made of dielectric (insulator). The rescuer should also be aware that an electric arc may strike him as the high voltage current creates this arc around the victim at a distance of 10 feet (1 foot equals 3.3 meters). It follows that the victim should not be touched until the current source is rendered harmless or removed from the patient with a non-conductive object, for example, a piece of dry wood.

When the victim is released, he must be immediately examined, breathing and cardiac activity checked and vital signs measured, and fresh air must be provided: unbutton the collar and belt of trousers or skirts, other tightening items of clothing, and put on a flat place. If heartbeat and breathing, even weak, persist, inhale ammonia you should spray your face cold water, rub the body with cologne, wrap the victim warmly, call a doctor immediately. While conscious, pain medications, sedatives and heart medications can be given. A bandage is applied to the skin affected by an electric burn, preferably from a sterile bandage moistened with diluted alcohol.

With severe respiratory and cardiac disorders, and even more so when they stop completely, you should immediately, without wasting a minute, start artificial ventilation and chest compressions and continue them until the full recovery of independent heartbeat and breathing. Sometimes it can take 3-4 hours or more. It is impossible to stop these resuscitation measures until the heartbeat and breathing are fully restored, at least until the doctor arrives. If necessary, it is necessary to continue them in the car during the transportation of the victim to the hospital. Only the appearance of signs of true biological death (crimson cadaveric spots on the skin of the underlying parts of the body and rigor mortis, which sharply impedes movement in all joints) can serve as an excuse for stopping attempts to revive the victim. In no case should you bury a person struck by electric shock or lightning in the ground or douse him with water - this causes cooling of the body, makes breathing and heart work, contaminates the burn surfaces with earth, which can lead to the development of tetanus and gas gangrene, and, what is the most most importantly, it excludes the possibility of immediately starting artificial respiration and heart massage, which are the only reliable and effective measures to combat “imaginary death” in severe electric shock.

3. Probable causes of defeat.

Possible causes of electric shock are:

1. Induced voltage:

High voltage transmission lines alternating current can induce high alternating voltage in nearby low-voltage power lines, communication lines, any extended conductors isolated from the ground. It can even occur in a car.

2. Residual voltage:

The power line has a large electrical capacity. Therefore, if the line is disconnected from the voltage, for some time the potential difference will still persist, and the simultaneous touching of different wires will lead to an electric shock. Discharging the line once with a grounded conductor may not be sufficient.

Hazardous residual voltage can be stored in radio equipment, which contains capacitors with a capacity of the order of a millifarad.

3. Static stress:

It occurs as a result of the accumulation of electrical charge on an insulated conductive object.

4. Step voltage:

It occurs between the legs due to the fact that they are at different distances from the wire that has fallen to the ground.

5. Damage to insulation. The reasons may be as follows:

manufacturing defects;

aging;

climatic influences, pollution;

mechanical damage, for example, by a tool;

mechanical wear, such as bending;

deliberate damage.

6. Accidental touch to a live part - due to ignorance, haste, distraction.

7. Lack of grounding:

In grounded equipment, in the event of insulation breakdown on the case, short circuit, and the fuses are blown.

8. Short circuit as a result of an accident:

For example, a strong wind or other cause can damage an overhead power line and drop the wire onto a parallel overhead wire of a radio or telephone, causing the considered low-voltage wire to be energized.

9. Inconsistency:

One individual works in the apparatus, the other applies voltage to it.

4. Dangerous factors at home and outside the home.

Not a single electrical injury is known from the use of electric shavers.

From household appliances most dangerous washing machines: they are installed in a damp room, near a water supply, and the electric cable is thrown, as a rule, just on the floor.

Electric heaters are dangerous. Electrical devices with a metal case are more dangerous than devices with a plastic case.

At home, deaths occur due to the simultaneous touch of a damaged electrical appliance and a hot water radiator or water pipe... (Conclusion: all pipes should be covered with a thick layer of paint.)

5. Security measures at home and outside the home.

Before connecting the electrical plug to the outlet, make sure that it is from the device that you are going to turn on. Also, after unplugging the plug, check that you are not mistaken. If the wires and cords from neighboring devices are similar, make them different: wrap with insulating tape or paint. Do not handle the power plug with a wet hand. Don't drive a nail into the wall unless you know where the hidden electrical wiring goes.

Make sure that sockets and other connectors do not spark, heat, or crackle. If the contacts are dark, clean them and correct the cause of the loose connection.

Avoid getting close to broken wire: step voltage may hit. If, nevertheless, you have to cross a dangerous zone near a wire lying on the ground, you need to do it by running: so that at the same time only one foot touches the ground.

When entering a trolleybus, do not touch its side with your hand. The trolleybus body can be energized due to insulation breakdown. It is better to jump into the trolleybus rather than enter; jump out, not go out: so that there is no situation when one foot is on the ground and the other is on the trolleybus step. Electric trains and trams are not dangerous in this respect, because they are always grounded.

From Jellinek writes: “ main feature electric trauma is that the tension of our attention, our strong will is able not only to weaken the effect of an electric current, but sometimes to completely destroy it. The crushing force of a falling beam or explosion cannot be weakened by courage and heroic endurance, but this is quite possible in relation to the action of an electric shock, if it occurs during a period of intense attention. Indeed, whoever hears a shot without seeing the shooter may die from a sudden shock, the one who looks at the shooter or shoots himself is not subject to shock. " (quoted by V.E. Manoilov)

6. Hazardous factors at work.

The most dangerous (in relation to electrical injuries) sectors of the economy - Agriculture and construction. The reasons are the widespread use of temporary electrical wiring (thrown to the ground or somehow suspended wires falling into puddles, damaged vehicles).

Approximately 30% of electrical injuries on installations with a voltage of 65 volts and below occur from the fact that, as a result of an error or breakdown, they turn out to be under a voltage of 220 or 380 volts. The surface of the insulating material can become electrically conductive through contamination and / or wetting.

The most common victims are electricians, radio operators, electric welders, construction workers. Many cases of electric shock occur in production facilities, in which chemically active substances that destroy insulation are used, as well as in dusty industrial premises (dust reduces the insulating properties of structures; an insulator covered with wet dirt becomes a conductor).

Wet rooms are dangerous. Insulation breakdown can occur in hidden wiring - in the place where the wire passes through a hole in the wall. Damage can occur from simultaneous contact with a damp surface (wall, floor) and a part of a plumbing or water heating.

More than half of the lesions in electric lighting installations occur when lamps are replaced.

Work injuries are more likely to occur at the beginning of the shift, before lunchtime, and towards the end of the shift. This can be explained by fatigue - a weakening of attention, a decrease in the body's resistance. Temporary laying of a cable on the floor, on the ground is dangerous. Fatalities have been reported due to live wires touching terminal box covers.

Due to the lack of uniformity in the designs of current-carrying devices, defeats occur when the usual actions are taken carelessly.

Bibliography

1. "Fundamentals of Student Medical Knowledge", a trial textbook for secondary educational institutions, edited by M.I. Gogolev ”, ed. "Education", Moscow, 1991.

2. "First aid for injuries and accidents", edited by V.А. Polyakova, ed. "Medicine", Moscow, 1990.

3. "First aid to the builder", edited by N.L. Khafizulina, ed. "Stroyizdat", Moscow, 1991.

4. "Civil Defense", a textbook, edited by A.T. Altunina, "Voenizdat", Moscow, 1984.

Completed by: student group No. 411 Serikova V.A.

Checked by: Krutova N.M.

• The effect of electric current on the human body
• Types of electric shock
• First aid for electric shock

The result of exposure to electric current on the human body depends on a number of factors:

• The electrical resistance of the human body The magnitude and duration of the course of the Genus and the frequency of the current Paths of current in the body Individual properties of a person and environmental conditions of industrial hangings
• Electrical resistance of the human body
• The magnitude and duration of the flow
• Kind and frequency of current
• Current paths in the body
• Individual properties of a person and environmental conditions of industrial hangings

The nature of the impact on humans can be seen in the table.

Current, mA

AC response

Onset of sensation: slight itching, tingling of the skin under the electrodes

DC response

The sensation extends to the wrist, slightly pulls the arm

Not felt

Painful sensations spread throughout the hand; slight cramps and mild pain in the arm

Not felt

The beginning of the sensation, the impression of a slight heating under the electrodes

Severe pain and cramps all over the arm, the arms are difficult, but can still be torn off the conductor

Barely tolerable pain, non-letting effect, pain increases with time

Increased heating sensation

Hands are paralyzed instantly. Very severe pain, difficulty breathing

Increase in heating

Very severe pain in arms and chest, extremely difficult breathing. With an increase in time, cessation of breathing and weakening of cardiac activity are possible. Sometimes loss of consciousness.

Increased heat and minor cramps

Breathing is paralyzed after a few seconds, the work of the heart is disrupted; fibrillation may occur

(with light weight - 50 kg or less)

Feeling of intense heat, pain and cramps in the hands. Barely tolerable pain when released from the guide.

Very strong heat, severe pain in the arms, chest, difficulty breathing. Hands cannot be taken off the guide due to severe pain

Cardiac fibrillation after 2-3 s, after a few seconds, respiratory paralysis

Same action but faster

Over 500

Respiratory paralysis

Breathing is paralyzed instantly, possible cardiac arrest, severe burns

Fibrillation after 2 - 3 s, respiratory paralysis

Electric current passing through the human body has:

• thermal
• electric
• biological
• mechanical
• information impact

In turn, each of them has a special description.

Thermal exposure leads to burns, heating and damage to blood vessels, brain, nerve tissues and other organs, which causes their functional disorder.

The electrolytic effect is manifested in the electrolysis of organic body fluids, including blood and plasma, accompanied by the formation of ions in the form of complex radicals, the destruction of red blood cells, which leads to hypoxia and disruption of the body as a whole.

The biological effect is expressed mainly in the violation of the internal bioelectrical processes of the body, causing irritation and excitement of living tissues, which is accompanied by involuntary convulsive contraction of the muscles of the heart, lungs and other human organs.

Mechanical impact, as a result of sharp convulsive movements, can occur: ruptures of the skin, blood vessels, dislocations, bruises and fractures.

Informational influence is a change in the functions of cells, which leads to the formation of tumors, a change in heredity.

Electrical injury is a painful condition of the body caused by exposure to electric current, the severity of electrical injury depends on the parameters of the current and the duration of its exposure.

Ultimately, all this leads to disruption and even complete cessation of the activity of the respiratory and circulatory organs.

Dangerous and harmful effects on people of electric current, electric arcs and electromagnetic fields are manifested in the form of electrical injuries and occupational diseases.

• Electric burns can be caused by the flow of current directly through the human body and the impact on it of an electric arc. In the first case, burns can be light in nature - reddening of the skin, blistering, etc. in the second case, it is severe, leading to necrosis of the affected area of ​​the skin and carbonization of the tissues.

• Electrical signs are puncture trauma with a well-defined gray or pale yellow color on the surface of human skin. Electro signs are painless and their treatment ends, as a rule, safely.
• Metallization of the skin is the penetration of the smallest particles of metal into the upper layers of the skin, melted under the action of an electric arc and electrochemical action. The affected area of ​​the skin, as a rule, comes off, and at the same time the painful sensations disappear.

• Mechanical damage is the result of sharp involuntary convulsive muscle contractions under the action of a current passing through the human body. As a result of this exposure, ruptures of the skin, blood vessels and nerve tissue can occur, as well as joint dislocations and bone fractures.
• Electric shock is the excitement of living tissues of the body, accompanied by an involuntary convulsive muscle contraction.

If electrical injuries are more in the nature of external damage to the body, then the electric shock causes internal damage to the entire human body.

There are four degrees of impact:

• Convulsive muscle contraction without loss of consciousness.
• convulsive muscle contraction with loss of consciousness.
• loss of consciousness and impaired heart or breathing, or both.
• clinical death. Lack of breathing and circulation.

• First aid.

Release of the victim from the effects of electric current

If a person touches the conductive part of the electrical installation and cannot independently free himself from the influence of the current, then those present need to help him, for which you should quickly disconnect the electrical wiring using a switch, a knife switch. If it is impossible to quickly disconnect the electrical installation from the network, the person providing assistance -

must separate the victim from the conductive part. In this case, it should be borne in mind that without applying the necessary precautions, you cannot touch a person who is in the current circuit, since you yourself can get under voltage.

First aid.

Proceed as follows: If the victim is exposed to a voltage of up to 1000V, the conductive

First aid in case of electric shock PRESENTATION MODEL A., CHAGLEY A.
TEACHER - V. N. KARTMAZOV
FIRST AID
ON ELECTRIC SHOCK

ELECTRICITY IS A PART OF OUR
EVERYDAY
LIFE.

The first step is to release the victim

THE FIRST STEP - RELEASING THE VICTIM
The first thing to do is
eliminate the current source, when
thus ensuring its own
safety. As it was already
said, often with electric shock
man can't let go
wire or object
energized.
The electricity needs to be turned off.
Or with a non-metallic stick
move the wire away from
the victim, or cut
wire ax with wood
with a pen, or wrap your hand dry
cloth and pull
the victim's clothes.

DIFFERENT VOLTAGES - DIFFERENT
DEGREES OF RISK
If the voltage level is up to 1000V, then by
opportunities should be quickly de-energized
source. If this cannot be done, then
cut the cable with an ax, or
another sharp object with an isolated
(wooden, plastic) handle.
It is allowed to use dry wooden
items (e.g. branches), pulling
with protected hands for dry
clothes. In the presence of electrical
items - dielectric gloves, galoshes and
etc. - use them.
At voltage levels above 1000V
it is necessary to use protective equipment,
use dielectric gloves and
bots. Also be sure to use
insulating bar or insulating
ticks, observing all the rules of use
these protective equipment.

The second step is to call an ambulance and first aid to the victim

THE SECOND STEP - CALLING A FAST AND
FIRST AID TO VICTIM

IF A PERSON IS IN CONSCIOUSNESS -
WHAT TO DO BEFORE ARRIVING
Soon
After liberation
the victim of the current must
establish the degree of damage and
according to the state
the victim to give him
medical assistance. If
the victim has not lost consciousness,
need to provide him with rest, and
in the presence of injury or damage
(bruises, fractures, dislocations, burns and
etc.) it is necessary to give him the first
assistance until a doctor arrives, or
deliver to the nearest medical
institution.

If a person is unconscious

IF A MAN WITHOUT CONSCIOUSNESS
If a person has lost consciousness, but
pulse and breathing are present, you should lay him on his side to
preventing tongue sinking,
unbutton tight clothes,
try to revive
cold water or ammonia
alcohol and watch it
condition.
* Artificial respiration is carried out,
if the victim is not breathing
alone, or when breathing
is infrequent and convulsive. *

IF THERE ARE NO SIGNS OF LIFE REANIMATION
If a person is missing
signs of life - the pupils are not
react to light, no breath
and pulse - to carry out cardiopulmonary resuscitation.
Carry out activities for
revitalization before recovery
status / arrival
medical staff or before
obvious sign of death, a decrease in body temperature to
ambient temperature
space, rigor mortis.

SIDE MEASURES - TREATMENT
BURNS, ETC.
All these activities are
paramount in importance,
helping a person with side
injuries (e.g. burns or
fractures) is made only
after normalizing it
states.
Two burns to be sought - place
input and output of current from the body.
Chill the burnt
body parts with running water and
wrap them in a clean cloth.
Treatment of electric shock burns
is carried out in the same way as for
thermal burns.

Slide 1

Slide 2

How an electric current acts on a person The fact that an electric current acts on a person was established in the last quarter of the 18th century. The danger of this action was first established by the inventor of the electrochemical high-voltage voltage source V.V. Petrov.

Slide 3

Electric current, electrical injury and electrical injury Electric shock is understood as an injury caused by the action of an electric current or an electric arc.

Slide 4

Electrical traumatism is characterized by the following features: a protective reaction of the body appears only after a person gets under voltage, that is, when an electric current is already flowing through his body; electric current acts not only in the places of contact with the human body and on the path of passage through the body, but also causes a reflex action, manifested in the disruption of the normal activity of the cardiovascular and nervous system, breathing, etc.

Slide 5

A person can get an electrical injury both by direct contact with live parts, and by being hit by a touch or step voltage, through an electric arc.

Slide 6

Electrical injury in comparison with other types of industrial injuries is a small percentage, but in terms of the number of injuries with severe, and especially fatal, it takes one of the first places. Leather metallization

Slide 7

The largest number of electrical injuries (60-70%) occurs when working on electrical installations with voltages up to 1000 V.

Slide 8

Causes of electric shock to a person The reasons for electric shock to a person are as follows: touching non-insulated live parts; to metal parts of the equipment that are energized due to damage to the insulation; to non-metallic objects that are energized; shock voltage step and through the arc.

Slide 9

Types of electric shock to a person Electric current flowing through the human body affects it thermally, electrolytically and biologically.

Slide 10

The thermal effect is characterized by tissue heating, up to burns; electrolytic - by the decomposition of organic fluids, including blood; the biological effect of electric current is manifested in the violation of bioelectric processes and is accompanied by irritation and excitation of living tissues and muscle contraction.

Slide 11

Electrical injuries are local injuries to tissues and organs: electrical burns, electrical signs and electrometallization of the skin.

Slide 12

Electrical burns occur as a result of heating human tissues by an electric current flowing through it with a force of more than 1 A. Burns can be superficial when affected skin, and internal - with the defeat of deep-lying tissues of the body. According to the conditions of occurrence, contact, arc and mixed burns are distinguished.

Slide 13

Electrical signs are spots of gray or pale yellow color in the form of calluses on the surface of the skin at the point of contact with live parts. Electrical signs are usually painless and subside over time.

Slide 14

Electrometallization of the skin is the impregnation of the surface of the skin with metal particles when it is sprayed or evaporated under the influence of an electric current.

Slide 15

Electric shock is the excitation of living tissues with an electric current, accompanied by an involuntary convulsive muscle contraction.

Slide 16

Clinical or "imaginary" death is a transitional state from life to death. In a state of clinical death, cardiac activity stops and breathing stops. The duration of clinical death is 6 ... 8 minutes. After this time, death of cells of the cerebral cortex occurs, life fades away and irreversible biological death occurs.

Slide 17

Electric shock is a severe neuroreflex reaction of the body to irritation with an electric current. With shock, deep disorders of breathing, blood circulation, nervous system and other body systems occur.

Slide 18

What determines the degree of action of electric current on the human body The outcome of the defeat also depends on the duration of the current flow through the person. With an increase in the duration of a person's stay under stress, this danger increases.

Slide 19

The individual characteristics of the human body significantly affect the outcome of an electrical injury. For example, a non-releasing current for some people may be a threshold perceptible for others. The nature of the action of the current of the same strength depends on the mass of a person and his physical development. It was found that for women the threshold current values ​​are approximately 1.5 times lower than for men.

1 slide

Analysis of the risk of electric shock Electrical network diagrams ZNT INT ZNT - a network with a grounded neutral point of the transformer; INT - network with an isolated neutral point (NT); (0 - 0) - zero protective conductor; R0 - working grounding of NT; Ri is the insulation resistance of the phase relative to earth; С - capacity; Ul - line voltage (380V); Uph-phase voltage (220V).

2 slide

Hazardous situations of electric shock 1. Accidental two-phase or single-phase contact with live parts. 2. Approach of a person at a dangerous distance to high voltage buses (according to the standards, the minimum distance is 0.7 m.) 3. Touching metal non-current-carrying parts of the equipment that may be energized due to damage to the insulation or erroneous actions of personnel. 4. Hit under the step voltage when a person moves along the area of ​​current spreading from a wire falling to the ground or shorting live parts to the ground.

3 slide

Two-phase touching live parts The most dangerous case is touching two phase conductors (a) and phase and neutral conductors (b). The current Ich passing through a person and the contact voltage Upr (V) at the human resistance Rh (Ohm): The contact voltage is the potential difference between two points of the circuit, which the person touches the surface of the skin. The path of the current is "hand-hand"

4 slide

Single-phase touching the network with ZNT This case is less dangerous than two-phase touching, since the resistance of shoes Rb and floor Rp is included in the defeat circuit. R = Rh + Rb + Rp Chain of defeat: Networks with ZNT are used at enterprises, in cities, in the countryside. Current path - "hand-foot"

5 slide

Single-phase touching a network with INT This case is less dangerous than for a network with ZNT with normal insulation resistance Ri (Ohm), but the danger for a long-distance network may increase due to the presence of a capacitive current. With the same R and each phase, the total insulation resistance is: Networks with INT are used with a small length of lines. They require constant monitoring of Ri. Current path - "hand-foot"