Electric shock presentation. First aid in case of electric shock. Types of electric shock.

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 electric shock is 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 a field, a taller tree in a forest, or 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, high voltage currents have 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 more extensive because the current must be expelled from the body, leaving a large opening. 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 an arc is formed, there is a 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 tissue effect 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 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 quickened 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, damage to 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. Pain in the area of electric burn is usually absent.

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 simplest way is to turn off the circuit with a switch or circuit breaker, unscrew 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 using 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 the heartbeat and breathing, even weak, persist, you can breathe in ammonia, spray your face with 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.

In case of severe respiratory and cardiac disorders, and even more so when they stop completely, one 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 arrival of the doctor. 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 (purple 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 to stop trying to revive the victim. In no case should you bury a person struck by an 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 AC transmission lines can induce high AC voltages in nearby low voltage transmission lines, communication lines, or any extended conductors that are isolated from earth. 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, a potential difference will still persist for some time, 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 the 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, distractions.

7. Lack of grounding:

In grounded equipment, in the event of insulation breakdown to the case, a short circuit occurs and the fuses burn out.

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.

Among household appliances, washing machines are the most dangerous: they are installed in a damp room, near a water supply, and the electric cable is thrown, as a rule, 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: cover all pipes 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 be 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 body of the trolleybus can be energized due to insulation breakdown. Better to jump into a trolley bus rather than enter; jump out, not get 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.

S. Jellinek writes: “The main feature of electrical trauma is that the tension of our attention, our strong will is able not only to weaken the effect of the 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 can 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 terms of electrical injuries) sectors of the economy are agriculture and construction. The reasons are the widespread use of temporary electrical wiring (thrown on the ground or somehow suspended wires falling into puddles, damaged by 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 electrical shock occur in industrial installations that use chemically active substances that destroy insulation, as well as in dusty industrial premises (dust reduces the insulating properties of structures; an insulator covered with damp dirt becomes a conductor).

Wet rooms are dangerous. Insulation breakdown can occur in hidden wiring - at 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 hot water heating.

More than half of the injuries in electric lighting installations happen when replacing lamps.

Work defeats 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 medical knowledge of students", 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. Polyakov, ed. "Medicine", Moscow, 1990.

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

4. "Civil defense", study guide, edited by A.T. Altunina, "Voenizdat", Moscow, 1984.

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The presentation on "Electrical Hazard Analysis" can be downloaded absolutely free of charge on our website. Project subject: Physics. Colorful slides and illustrations will help you engage your classmates or audience. To view the content, use the player, or if you want to download the report, click on the corresponding text under the player. The presentation contains 7 slide (s).

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Slide 1

Electrical Hazard Analysis

Electrical network diagrams

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).

Slide 2

Dangerous situations of electric shock

1. Accidental two-phase or single-phase contact with live parts.

2. Approaching a person at a dangerous distance to high voltage buses (according to the standards, the minimum distance is 0.7 m.)

3. Touching non-conductive metal 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 short-circuiting of current-carrying parts to the ground.

Slide 3

Two-phase contact with live parts

The most dangerous case is touching the two phase wires (a) and the phase and neutral wires (b).

The current Ich passing through a person and the contact voltage Upr (V) with a person's resistance Rh (Ohm):

Touch voltage is the potential difference between two points in the circuit that a person touches with the surface of the skin.

Current path - hand-hand

Slide 4

Single-phase contact to the network with ZNT

This case is less dangerous than a two-phase touch, since the resistance of the shoes Rb and the 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"

Slide 5

Single-phase contact to the 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.

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"Electric current" - Electrophthalmia. General electrical injuries. Electrical burn. Mechanical action of the current. Electric shock. Electric shock. Factors affecting the outcome of electric shock. The rules of movement in the "step voltage" zone. Electrometallization of the skin. Types of electric shock.

"On the pond" - To swim or not to swim? It is not only useless for everyone to accumulate on the edge of the ice hole, but also dangerous. The main hazards in water bodies. Ice condition monitoring. Salvation - whose handiwork? Learning to identify hazards in water bodies at different times of the year. Precautions when driving on ice. Bathing rules in equipped and unequipped places.

"Crossing the road" - Cross the street at a calm pace only along the pedestrian crossing. Green. Traffic light signal allowing for crossing is green. Never cross the road in front of a nearby vehicle. How do you live? Is it easy to be a pedestrian? School. Are there rules for pedestrians? How do you walk on a zebra? Are you running into the yellow light again?

"Traffic on the roads" - Take your time on the road And forget your skateboards. The road was covered with gravel. There is a carriageway here! There used to be no sidewalks on the streets. The carriages were pushing and crushing people. Take a closer look: Once to the left, once to the right. The pavement rages in motion: Cars are running, trams are hurrying. Green light opened the way: Guys can cross!

"Earthquakes and volcanoes" - It is necessary to beware of balls of hot dust and gases (bombs). Magma poured out to the surface. Safe conduct during an earthquake. Tremors and vibrations of the earth's surface. Ejection of steam, gases, magma, rocks from the volcano. Gases and ash escaping from the crater from time to time.

"Study of traffic rules" - Record keeping. Folder number 2. Media newspapers. Regulations on the school round of the competition "Safe wheel". Methodical recommendations for conducting classes "Safety Minutes". Folder number 8. Development of extracurricular activities. From the experience of GOU SOSH No. 948 of the Southern Administrative District of the city of Moscow. Competition protocol. Folder number 3.

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