Electric shock. The main causes of electric shock in everyday life Causes of electric shock
In the late 70s of the century before last, the first human death from electricity was recorded. A lot of time has passed since then, but the number of people affected by the same cause is only increasing. In connection with these events, people were forced to create a list of rules for how to behave with electricity. For many years, future electricians have been trained in specialized educational institutions and immediately after completion of which they undergo an “internship” in production and, of course, pass the final test exam, after which they receive a license and can independently work with electric current. What is most surprising is that no one in this world is immune from mistakes. Even a highly qualified specialist can easily get injured due to carelessness. Can you say with confidence that with any problem related to electricity, you will solve it with ease and accuracy? If not, then this article is just for you! Next, we will talk about what causes of defeat exist. electric shock and basic protective measures at home.
What is electric current?
Concentrated movement of charged particles in space under the influence of an electric field. This is how the term electric current is explained. What about particles? So they can be absolutely anything, for example: electrons, ions, etc. Everything depends only on the object in which this very particle is located (electrodes/cathodes/anodes, etc.). If we explain it according to the theory of electrical circuits, then the reason for the occurrence of electric current is the “purposeful” movement of charge holders in a conducting environment when exposed to an electric field.
How does electricity affect the human body?
A strong electric current that is passed through a living organism (human, animal) may cause a burn, or may cause electric shock through fibrillation (when the ventricles of the heart do not contract synchronously, but each “on its own”) and ultimately this will lead to to death.
But if you look at the other side of the coin, electric current is used in therapy, for resuscitation of patients (during ventricular fibrillation, a defibrillator is used, a device that simultaneously contracts the muscles of the heart through electricity, thereby forcing the heart to beat in its “usual” rhythm), etc. etc., but that’s not all. Every day, starting from our birth, electricity “flows” into us. It is used by our body in nervous system to transmit impulses from one neuron to another.
Rules for handling electrical appliances
In essence, we will offer you a list of rules of what should and should not be done when children interact with electrical devices, BUT this does not mean that as an adult you can neglect these rules! So, let's begin!
When interacting with electrical devices IT IS FORBIDDEN:
- Touch exposed wires.
- Activate broken electrical appliances, because if something happens they can cause a fire or shock you.
- Touch wet hands to the wires (especially if they are bare).
NECESSARY:
- Remember that under no circumstances should you pull the wire in order to pull it out of the outlet.
- When leaving home, check to see if any electrical appliance has been left on.
- If you are a child, be sure to call an adult if, while plugging in an electrical appliance, you see that the wire or the electrical appliance itself begins to smoke.
The main causes of electric shock
An electric shock can occur when a person is near the place where live parts connected to the network are located. It can be described as the irritation or interaction of body tissues with electricity. Ultimately, this will lead to completely involuntary (convulsive) contractions of the human muscles.
There are a number of reasons for human injury from electricity, such as: the possibility of injury when replacing a light bulb in a lamp connected to the network, the interaction of the human body with equipment that is connected to the network, long (continuous) operation of electrical appliances, and of course people who do not fix everything themselves depending on whether it is successful or not (in other words, “Homemade”). Let's start by listing the main causes of electrical damage, and then we will figure out in order what the essence of these problems is.
The main causes of electric shock are:
- Human interaction with faulty household electrical appliances.
- Touching exposed parts of an electrical installation.
- Incorrect voltage supply to the work site. That is why in production you need to hang a special one, as in the picture below:
- The appearance of voltage on the body of equipment, which under normal conditions should not be energized.
- Electric shock due to a faulty power line.
- Replacing a light bulb in a lamp connected to the network. People can be injured due to the fact that during a banal light bulb change they simply forget to turn off the light. You need to remember that before you change a light bulb, you first need to turn off the light.
- Interaction of the human body with equipment that is connected to the network. There have been cases where people were injured from this option. Everything is simple here. When interacting with an electrical appliance (for example, a washing machine), you hold on to a part of the house that is grounded (for example, a pipe) with your other hand. Thus, a current will pass through your body, which will cause damage. To prevent this from happening, it is recommended.
- Long (continuous) operation of electrical appliances. In fact, cases of damage in this way are minimal. The problem is this: appliances such as a washing machine from long work may break if washing machine at least leak. To avoid such incidents, simply check that the devices are working properly more often. We talked about this in the corresponding article.
- People who fix everything themselves. This is considered the most common problem of all, because today, using the Internet, you can find a lot of instructions like “How to do...”, even on our website in the section. However, the majority of people who start constructing something do not have the proper knowledge and, due to ordinary carelessness, are injured or even maimed.
- can be very dangerous for you or your equipment; in the end, voltage surges can cause a fire or worse - an electrical shock. So how to deal with this? Today, there are three main ways to reduce the consequences of power surges, namely: , and . These three things in everyday life will serve you and your equipment as protection from power surges.
Characteristics of human electric shock injuries. Electrical resistance of the human body. 2
Main causes of electric shock. 3
Methods and means used. 4
for protection against electric shock. 4
when touching metal non-current-carrying parts, 4
under tension. 4
Organizational measures to ensure the safety of work in electrical installations. 4
Technical measures to ensure safe performance of work in existing electrical installations. 4
Characteristics of human electric shock injuries. Electrical resistance of the human body
Electric current, passing through the human body, has biological, electrochemical, thermal and mechanical effects.
The biological effect of current is manifested in irritation and excitation of tissues and organs. As a result, skeletal muscle spasms are observed, which can lead to respiratory arrest, avulsion fractures and dislocations of the limbs, and spasm of the vocal cords.
The electrolytic effect of current manifests itself in the electrolysis (decomposition) of liquids, including blood, and also significantly changes the functional state of cells.
The thermal effect of electric current leads to burns of the skin, as well as death of the underlying tissues, including charring.
The mechanical effect of the current manifests itself in tissue separation and even separation of body parts.
Electrical injuries can be divided into local, general (electrical shocks) and mixed (local electrical injuries and electrical shocks simultaneously). Local electrical injuries account for 20% of the accounted electrical injuries, electrical shocks - 25% and mixed - 55%.
Local electrical injuries- clearly defined local damage to body tissues, most often these are superficial injuries, i.e. damage to the skin, sometimes soft tissues, as well as joint capsules and bones. Local electrical injuries are cured, and the person’s performance is restored fully or partially.
Typical types of local electrical injuries- electrical burns, electrical marks, skin metallization, electroophthalmia and mechanical damage.
The most common electrical injuries are electrical burns. They account for 60 - 65%, and about 1/3 of them are accompanied by other electrical injuries.
There are burns: current (contact) and arc.
Contact electrical burns, i.e., tissue damage at the entry, exit and along the path of electric current occurs as a result of human contact with a live part. These burns occur when operating electrical installations of relatively low voltage (no higher than 1-2 kV), and they are relatively mild.
Arc burn caused by the influence of an electric arc, creating high temperature Arc burns occur when working in electrical installations of various voltages and are often the result of accidental short circuits in installations above 1000 V and up to 10 kV or erroneous personnel operations. Damage occurs from the flame of an electric arc or clothing that catches fire from it.
There may also be combined injuries (contact electrical burn and thermal burn from an electric arc flame or flaming clothing, electrical burn in combination with various mechanical injuries, electrical burn simultaneously with thermal burn and mechanical injury).
According to the depth of damage, all burns are divided into four degrees: first - redness and swelling of the skin; the second - water bubbles; third - necrosis of the superficial and deep layers of the skin; fourth - charring of the skin, damage to muscles, tendons and bones.
Electrical signs are clearly defined spots of gray or pale yellow color on the surface of the skin of a person exposed to current. The signs have a round or oval shape with a recess in the center. They come in the form of scratches, small wounds or bruises, warts, hemorrhages in the skin and calluses. Sometimes their shape matches the shape of the live part that the victim touched, and also resembles the shape of lightning. In most cases, electrical signs are painless and their treatment ends well. Signs occur in approximately 20% of electric shock victims.
Skin metallization- penetration into its upper layers of metal particles melted under the action of an electric arc. This is possible in case of short circuits, disconnectors and circuit breakers tripping under load, etc.
The affected area of the skin has a rough surface, color
which is determined by the color of metal compounds that come into contact with the skin:
green - in contact with copper, gray - with aluminum, blue -
green - with brass, yellow-gray - with lead.
Metallization of the skin is observed in approximately 10% of victims.
Etectroophthalmia- inflammation of the outer membranes of the eyes as a result of exposure to a powerful stream ultraviolet rays. Such irradiation is possible in the presence of an electric arc (for example, during a short circuit), which is a source of intense radiation not only of visible light, but also of ultraviolet and infrared rays. Electroophthalmia occurs relatively rarely (in 1-2% of victims), most often during electric welding work.
Mechanical damage occurs as a result of sharp, involuntary, convulsive muscle contractions under the influence of current passing through the human body. This may result in skin ruptures, blood vessels and nervous tissue, as well as joint dislocations and bone fractures. Mechanical damage - serious injury; their treatment is long-term. They occur relatively rarely.
Electric shock- this is the stimulation of body tissues by an electric current passing through it, accompanied by muscle contraction.
Distinguish four degrees of electric shock:
I - convulsive muscle contraction without loss of consciousness;
II - convulsive muscle contraction with loss of consciousness, but with preserved breathing and heart function;
III - loss of consciousness and impaired cardiac activity or breathing
nia (or both)
IV - clinical death, i.e. lack of breathing and blood circulation,
The danger of exposure to electric current to a person depends on
the resistance of the human body and the voltage applied to it, the strength of the current, the duration of its influence, the path of passage, the type and frequency of the current, the individual properties of the victim and other factors.
The electrical conductivity of different tissues of the body is not the same. Cerebrospinal fluid, blood serum and lymph have the highest electrical conductivity, followed by whole blood and muscle tissue. Poor conduction of electric current internal organs having a dense protein base, brain matter and adipose tissue. The skin has the greatest resistance and, mainly, its upper layer(epidermis).
The electrical resistance of the human body with dry, clean and intact skin at a voltage of 15 - 20 V ranges from 3000 to 100,000 Ohms, and sometimes more. When the top layer of skin is removed, the resistance decreases to 500 - 700 Ohms. At complete removal skin resistance of internal body tissues is only 300 - 500 Ohms. For calculations, the resistance of the human body is assumed to be 1000 Ohms.
The resistance of the human body depends on the gender and age of people: in women this resistance is less than in men, in children - less than in adults, in young people - less, HIGH IN THE ELDERLY: THIS is explained by the thickness and degree of coarsening of the upper layer of skin.
On electrical resistance The type of current and its frequency also influence. At frequencies of 10 - 20 kHz, the upper layer of skin practically loses its resistance to electric current.
Main causes of electric shock
1. Accidental contact with live parts that are energized as a result of: erroneous actions during work;
malfunction of protective equipment with which the victim touched live parts, etc.
2. Appearance of stress on metal structural parts
electrical equipment as a result of:
damage to the insulation of live parts; network phase short circuit to ground;
falling of a live wire onto structural parts of electrical equipment, etc.
3. Appearance of voltage on disconnected live parts in the
result:
erroneous activation of a disabled installation;
short circuits between disconnected and energized live parts;
lightning discharge into an electrical installation, etc.
4. Appearance step voltage on the plot of land where it is located
person, as a result:
phase-to-ground fault;
removal of potential by an extended conductive object (pipeline, railway rails);
malfunctions in the device protective grounding and etc.
Step voltage - the voltage between two points of a current circuit, located one step apart from each other, on which a person is simultaneously standing.
The highest value of the step voltage is near the fault point, and the lowest is at a distance of more than 20 m.
At a distance of 1 m from the ground electrode, the step voltage drop is 68% of the total voltage, at a distance of 10 m - 92%, at a distance of 20 m - practically equal to zero.
The danger of step voltage increases if the person exposed to it falls: step voltage increases, since the current no longer passes through the legs, but through the entire human body.
Methods and means used
for protection against electric shock
when touching metal non-current-carrying parts,
under tension
To protect against electric shock when touching metal non-current-carrying parts that are energized, use following methods and means:
protective grounding, grounding, potential equalization, system of protective conductors, protective shutdown, insulation of non-current-carrying parts, electrical separation of the network, low voltage, insulation monitoring, compensation of ground fault currents, personal protective equipment.
Technical methods and means are used separately or in combination to provide optimal protection.
Organizational measures to ensure the safety of work in electrical installations
Organizational measures to ensure safe work in electrical installations are:
registration of work with a work permit, order or list of work performed in the order of current operation;
permission to work;
supervision during work;
registration of breaks in work, transfers to another workplace, finishing work.
Technical measures to ensure safe performance of work in existing electrical installations
In accordance with the requirements of the Safety Rules for the operation of consumer electrical installations, to prepare the workplace when working with voltage relief, the following technical measures must be carried out in the specified order;
the necessary shutdowns have been made and measures have been taken to prevent the supply of voltage to the work site due to erroneous or spontaneous switching on of the switching equipment;
prohibiting posters are posted on manual drives and on remote control keys of switching equipment;
checked that there is no voltage on live parts that must be grounded to protect people from electric shock;
grounding is applied (grounding blades are included, and where they are absent, portable grounding connections are installed);
Electric shock occurs when an electrical circuit is completed through the human body. A two-phase touch is the case when a person touches two wires, and a single-phase touch is when a person touches one wire while having contact with the ground. With a two-phase touch, a linear voltage UЛ is applied to the human body and a large current flows through it. If we assume that the average resistance of the human body is R = 3000 Ohm, then the current passing through it is equal to:
electricity injury arc current
This current is deadly. With a single-phase touch in a network with a grounded neutral wire, a series circuit is formed from the resistances of the human body, shoes, floor and grounding of the neutral wire of the current source. Not linear, but phase voltage is applied to this circuit. In this case, everything depends on the resistance of the shoes and the floor, since the grounding resistance of the neutral wire is usually very small. If a person in damp or nailed shoes stands on damp ground or on a conductive floor, then the resistance of the shoes and the floor is negligible compared to the resistance of the person and the current flowing through the body will be equal to:
This current is also deadly.
Factors and causes of electric shock
Electric shock can be caused by touching something bad insulated wires lighting electrical network or to contacts electrical appliances. Touching the bare wires with a damp hand enhances the effect.
In most cases, a person who touches exposed wires cannot tear himself away from them, as his hand clenches convulsively. The rescuers' task is first of all to immediately turn off the current or pull the victim away from the wires. The current can be turned off by unscrewing the plug, and if it is not there, you need to cut the current-carrying wire with an ax wooden handle. If the victim is not standing on the floor, but on a stool, chair or stepladder, then it is necessary to take measures to ensure that he does not fall, and also to provide some personal safety rules. You only need to grab the victim’s dry clothes, placing a dry board or other poorly conductive object under your feet. It is advisable to put rubber gloves on your hands, and if you don’t have them, then wrap your hands in a rubberized raincoat or, in extreme cases, a thick, dry rag.
Having isolated the victim from the action of the current, they act according to his condition: if he is unconscious and not breathing, it is necessary to perform artificial respiration until the doctor arrives. The absence of breathing and pulse does not indicate the death of the victim. There have been cases of people returning to life after several hours of a seemingly hopeless state. As soon as the victim begins to breathe on his own, he must be put to bed and covered warmly.
Lightning damage is a special case of electric shock. high voltage. Usually these cases are fatal, but nevertheless it is necessary to urgently call a doctor, and until he arrives, perform artificial respiration, as in the case of electric shock. If the victim has burns, they should be lightly bandaged. Burying someone struck by lightning into the ground is not only useless, but also harmful, since the mass of earth piled on the injured person will worsen his condition, and such a technique can completely deprive someone seriously injured of the possibility of returning to life.
A person who has absolutely no understanding of the principles of how electricity works runs the risk of getting an electric shock when performing some installation. Typically, accidents are caused not only by the inexperience of the installer, but also by the malfunction of some communications, including the installed grounding or lack thereof.
Often, the resulting injury is characterized by death, the percentage of which varies from 5 to 15%. Therefore, we must conclude that it is better to trust the work of repairing electrical networks to qualified specialists.
Important! A person working with electrical network, you should completely protect yourself from possible troubles.
Electric current can be very dangerous for a person’s life and health. In order to assess the situation as a result of an electrical injury, we suggest studying what an electrical injury is like:
What current is unsafe?
The consequences of an electric shock can be the most unexpected, but they depend on the nature of the current and its work force. Considered the most dangerous alternating current as opposed to constant, although they have the same power. The voltage that leads to death has a force above 250 Volts with a simultaneous frequency of 5 Hz. The risk of electric shock may be reduced during certain periods.
Until today, experts have not been able to establish exact value voltage indicator that can cause harm to a person in the form of electrical injury. By the way, there are several recorded cases where an electric shock with a voltage of 47 volts resulted in a fatal outcome.
Factors influencing the outcome of electric shock
There are several factors that significantly influence the consequences that can happen to a person after an electric shock.
Such very deplorable factors influencing the degree of electric shock cause a lot of problems, and possibly inevitable tragedies.
Hidden consequences that appear after an electric shock
In some cases, the features of electric shock are extensive and secretive. Despite the fact that this situation occurs in 1 in 100 cases, it is better to play it safe and determine what these consequences threaten.
Important! Some features that appear covertly after an electric shock cannot be diagnosed.
None of us is able to predict which organs will be affected by electric current. Even if you do not feel pain in a certain area, it is far from a fact that the electric current did not go there.
A person exposed to high current power feels strong convulsive muscle contractions throughout the body. Due to this, cardiac fibrillation often occurs and the functioning of nerve impulses is disrupted. Very often the resulting electrical injuries are aggravated, as a result of which they can reach the highest levels. The skin is destroyed, muscle tears appear due to strong convulsive reactions.
Danger and types of electrical injuries
Electrical injuries resulting from electric shock are conventionally divided into general and local.
General electrical injury is a characteristic electric shock due to exposure to high voltage, which can spread both to the entire body and to its individual parts. Often these situations require hospitalization of the patient and constant medical supervision, and death is not uncommon.
Local electrical trauma is a type of electric shock that results in burns, metallization of the skin, and tissue ruptures during convulsive contractions. This group includes deep electrical burns that penetrate deep into the muscle tissue.
First aid for electrical injury or how to save the life of a victim
Of course, helping a person who has been electrocuted must be done immediately. Let's consider what should be done in such cases:
Preventive measures and how to avoid electrical shock
First of all, preventive measures should include studying safety precautions when working with electrical installations and wiring. Even if a person is not a professional installer, he must be instructed in all cases, and also provided with special clothing. When you do work with electricity at home, you should purchase rubber gloves and, if possible, a non-conductive suit; this will definitely come in handy around the house.
The causes of electrical accidents are many and varied. The main ones are:
1) accidental contact with exposed live parts. This can happen, for example, when performing any work near or directly on live parts: in the event of a malfunction of protective equipment through which the victim touched live parts; when carrying long metal objects on your shoulder, which can accidentally touch uninsulated electrical wires located at a height accessible in this case;
2) the appearance of voltage on metal parts electrical equipment (housings, casings, fences, etc.), which in normal conditions are not under voltage. Most often, this can occur due to damage to the insulation of cables, wires or windings of electrical machines and devices, leading, as a rule, to a short circuit to the housing;
3) an electric arc that can form in electrical installations with a voltage of over 1000 V between a live part and a person, provided that the person is in close proximity to live parts;
4) the occurrence of a step voltage on the surface of the earth when a wire is shorted to the ground or when current flows from the ground electrode into the ground (in the event of a breakdown on the body of grounded electrical equipment);
5) other reasons, which include such as: uncoordinated and erroneous actions of personnel, leaving electrical installations energized without supervision, admission to repair work on disconnected equipment without first checking the absence of voltage and faulty grounding device, etc.
The main measures to eliminate the causes of electric shock discussed above and ensure the protection of operating personnel are:
* ensuring that live parts under voltage are inadmissible for accidental contact. For this purpose, live parts must be located at an inaccessible height; fencing and insulation of live parts are widely used;
* application of protective grounding and grounding of electrical installations;
* automatic shutdown, the use of reduced voltage, double insulation, etc.;
* use of special protective equipment - portable devices and devices, means personal protection;
* clear organization safe operation electrical installations.
End of work -
This topic belongs to the section:
Life safety
Ministry of Education and Science of the Russian Federation.. Federal State Budgetary educational institution higher vocational education Samara State Aerospace..
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Sprinkler and deluge systems are used to automatically extinguish fires with water. The sprinkler installation consists of devices supplying water, main and
Extinguishing with foam
Currently, chemical and air-mechanical foam are widely used to extinguish flammable and combustible liquids. Chemical foam is formed as a result of a chemical reaction
Extinguishing fires with chemical foam
To extinguish small fires, manual chemical foam fire extinguishers of the OKP-10 type are widely used (Figure 2). The fire extinguisher body contains the alkaline part of the charge - an aqueous solution
Extinguishing fires with air-mechanical foam
Air-mechanical foam, unlike chemical foam, is formed as a result of intensive mixing of air with an aqueous solution of a foaming agent in special devices - foam mixers in air
Extinguishing fire with carbon dioxide
Carbon dioxide is used to extinguish flammable and combustible liquids, solids, and electrical installations under voltage. Carbon dioxide does not spoil substances in contact with it,
Extinguishing fires with halogenated hydrocarbons
Currently, highly effective compounds based on halogenated hydrocarbons, such as tetrafluorodibromomethane (freon 13B and 114B2), these bromide, are increasingly being used to extinguish fires.
Extinguishing fires with powder compounds
Powder compositions are intended for extinguishing fires of flammable liquids and gases, alkali and alkaline earth metals and their carbides, live electrical installations, and valuable items (archives, museums).
Fire communications and alarm
The fastest and most reliable way to notify about a fire is electrical fire alarm(EPS). EPS consists of the following main parts: detectors installed
Labor protection legislation
Main legislative documents in this industry to date are the “Basic legislation on labor protection” and the Labor Code of the Russian Federation. Laws for this industry
Principles, methods and means of ensuring safety
In structure general theory security, a certain hierarchy of principles, methods and means of ensuring security has developed. A principle is an idea, a thought, a basic position.
Analysis of industrial injuries
When analyzing the causes that led to an accident, the following methods are used: Statistical method, which processes statistical data on
Standardization in the field of safety
A special place among regulatory documents In the field of occupational safety, the system of occupational safety standards - SSBT, the structure of which is presented in Fig. 2, occupies a position. A special role belongs
Construction norms and rules (SNiPs)
For example: - SNiP 11-4-79 (part 2. Design standards. Chapter 4. Natural and artificial lighting); - SNiP 2.09.02-85 - Industrial buildings; - SNiP 2.01.02-85 - Against
Safety briefing
Instructions and standards of the enterprise on labor protection The employer is obliged to provide workers with instructions on labor protection. this work must implement
The effectiveness of measures to ensure safety at work
Measures to improve working conditions include all types of activities aimed at preventing, eliminating or reducing the negative impact of harmful and dangerous production facts
Economic results
· Savings by reducing funds for temporary disability benefits. · Annual savings due to reduced injury rates · Fund savings wages V