Since 1879, the safety of people working with electricity has been a hot topic. It was then that the first case of death of a person from exposure to electric current was registered.
Since then, the number of victims has been increasing all the time. On the basis of sad statistics, safety rules have been created, each item in which is based on someone's tragedy.
Electricians of various professions are trained for several years by schools, technical schools, institutes and specialized courses. After that, graduates of institutions undergo internships at energy enterprises, pass numerous exams and tests. Only after that they are allowed to work independently.
However, even electricians who have worked for many years with higher fifth safety group due to mistakes and inattention, sometimes they get serious electrical injuries.
Unfortunately, an ordinary person does not have such theoretical training and practice of working with electricity. And he does not need to know all the intricacies of our profession. But, to follow the elementary rules, which, by the way, everyone is told from school and kindergarten, is simply necessary.
I would like the readers of the articles of this site to become active preachers of the safe handling of electrical installations, not only in production, but also in everyday life, among their loved ones. The word of a specialist, backed up by life facts, is always well imprinted in the memory and perceived with more confidence than ordinary text. It can never be redundant.
Human psychology quickly adapts to everything familiar: electricity surrounds us everywhere, making life easier, and malfunctions in it rarely occur, and usually cause little harm. But until a certain point...
Therefore, tell your surroundings once again the main causes of electric shock in everyday life. Be sure: your words will save loved ones from an accident.
What is forbidden to do with electrical appliances in the home
Damaged appliances
Any electrical receiver has a layer of insulation. It covers the most critical places of the wire even with several layers in order to exclude contact of human skin with the potential of the mains. But, careless handling of electrical wiring, mechanical impact on it, overheating from improper loads or loose contacts violate its dielectric properties.
Do not touch the bare metal of a wire that is energized or use switches, sockets and plugs with broken cases. This is a direct prerequisite for electrical injury.
To exclude such cases, conduct periodic inspections of the condition of all devices and electrical wiring. Better yet, check the condition of its insulation by measurements. But this is a rather dangerous event and can only be entrusted to specialists.
Repair work
All faulty electrical equipment must be taken out of service to eliminate breakdowns. And only a trained person can do it. Otherwise, the consequences of unskilled repairs can be unpredictable.
Careful handling of equipment
Electrical appliances connected to the network must not be disassembled. Be especially careful with the power cord. It is unacceptable to pull on it in order to move the electric stove, iron or pull the plug out of the socket.
In this way, you can easily arrange a short circuit. Power cords are often subjected to twisting, kinking, and stress. heating. Breaks and breaks can occur inside them. They can break good contact, cause sparks, leading to fire.
You must use your electrical appliances with care.
Replacing light bulbs in fixtures
Every adult, not to mention children, should know that it is forbidden to repair live electrical equipment. Any operation on electrical receivers must be performed with the power off.
Often people get injured when they screw in / turn out ordinary incandescent bulbs. The light switch must always be switched off.
The metal thread of the base can jam in the cartridge, and its fastening with the bulb can loosen. As a result, the glass part will turn, the internal voltage supply threads, made of open metal, will touch each other, creating a short circuit.
Contact with the body of devices connected to voltage
In a two-wire network (phase, zero) operated, when the insulation breaks down on the case, a life-threatening potential appears. If a person touches such a device with one part of the body (the figure shows a dishwasher), and the other part touches the structural elements of the building connected to the ground (in the picture - a pipeline), then a current will flow through his body along this path.
To prevent such injuries, there are protections that respond to the appearance of leakage currents. in such wiring it will reduce the damaging effect of the current, and in a circuit equipped with a protective PE conductor according to the TN-S or TN-C-S systems, it will prevent an accident.
Proper connection to the ground loop of all housings of household appliances, the use of a potential equalization system is the key to preventing electric shock to residents.
Long-term operation of electrical appliances
Modern refrigerators, freezers and some household appliances are designed to perform a continuous technological cycle. They are equipped with automatic control systems for this.
Even such devices can break down and need periodic monitoring by the owner. Burnt out electric motors, floors flooded with water, or cases of flooding of neighbors from below are clear evidence of this.
For working machinery and electrical equipment, inspection by a person is still required.
Homemade
We love to make things with our own hands. Now it is very easy to find a lot of advice on how to make a home-made machine, heating, welding ... But are we qualified to do all this not only working, but also safe for operation? Certainly not always.
The designs of many homemade heaters are not only fire hazardous, but can create electrical injury.
In any case, before putting home-made electrical appliances into operation, it is important not only to measure the resistance of electrical insulation, but also to test it. This is done by specialized electrical laboratories.
Maintaining electrical wiring protection
In all residential premises, when commissioning the electrical circuit, introductory shields are installed. They, as a rule, have a built-in electric meter and circuit breakers or fuses.
They must be kept in working order. This requirement is especially relevant for old houses in rural areas, where you can still find working, but obsolete electrical panels with an induction meter and two cork fuses. In them, instead of industrial fuse-links, the owners install home-made "bugs" - pieces of randomly selected wires.
Often their denominations are overstated: so as not to change once again in case of burnout. It is for this reason that they do not always quickly turn off the resulting short circuit, and in some cases do not work at all.
The same requirement applies to the settings of circuit breakers. Their selection, configuration and performance testing is an important element of electrical safety.
Children
They are always inquisitive, mobile, actively climb into all accessible and even forbidden places. In this way they learn about the world around them, master it. But is it always possible for an adult to keep track of the behavior of the baby, to protect him from falling under the action of the current? How to avoid accidents?
Parents need to take into account the age of the child and his development. Children under three years old should be excluded from access to electrical appliances by furniture elements, partitions, fences. Be sure to indicate the restricted areas and suggest that they should not be included there.
All contacts of electrical outlets must be closed with dielectric plugs. After all, kids can stick a nail, pin or other piece of metal there.
Children of all ages need to be persistently explained the rules for the safe handling of electricity in everyday life and on the street. To this end, a lot of books have been written for them and many educational cartoons have been shot. For example, "Advice from Aunt Owl."
Such video tutorials are created by specialists taking into account the specifics of child psychology. They are informative and memorable. Especially when parents give incidental explanations, and after watching it together, they share comments and ask leading questions.
In conclusion of the article, I would like to once again turn to electricians: for sure, based on your own experience, you also know the causes of electric shock in everyday life. Share them with your loved ones! Your advice will always be taken. They will help protect a person from getting electrical injuries.
An electric shock occurs when an electrical circuit is closed through the human body. The most common cases of electric shock in cases where a person touches two or one wire, while having contact with the ground. In the first case, the touch is called two-phase, in the second - single-phase.
With a two-phase touch (Fig. 10-1), a person is exposed to line voltage, so a large current flows through him
where is the line voltage and the average (with good contacts) resistance of the human body. The current in this case is deadly, although a person can be well isolated from the ground.
In the case of a single-phase contact in a network with a grounded neutral wire (Fig. 10-2), a series circuit is formed from the resistances of the human body, shoes, floor and grounding of the neutral (neutral wire) of the current source. A phase (and not linear, as in the previous case) voltage is applied to this circuit. However, if a person in wet or nailed shoes stands on damp ground or on a conductive floor, then these resistances, like the resistance (10 ohms), are negligible compared to the resistance of the human body. Current will flow in this circuit:
This current is deadly.
However, if a person is wearing special rubber shoes and is on a dry wooden floor, then, assuming the resistance of the shoes is 45,000 ohms and the floor is 100,000 ohms, in the circuit under consideration we get the current value:
i.e. harmless to humans. The last case shows how important it is for safety reasons to use non-conductive shoes and especially an insulating floor.
In the case of a single-phase contact with a network with an isolated neutral, the circuit closes through the human body and through the imperfect insulation of the network wires (Fig. 10-3). In good condition, the insulation has a very high resistance, so such a touch should not be dangerous. This is true only for normal (fail-safe) networks. In networks with a voltage of 1000 V or more, the capacitance between phases and ground can create a large capacitive current that is dangerous to humans.
The voltage between two points in the current circuit, which are simultaneously touched by a person, is called the touch voltage. The danger of such a touch, assessed by the value of the current passing through the human body, or by the voltage of the touch, depends on a number of factors: the circuit for closing the current circuit through the human body, the voltage of the network, the circuit of the network itself, the mode of its neutral (i.e. grounded or isolated neutral ), the degree of isolation of current-carrying parts from the ground, as well as the value of the capacitance of current-carrying parts relative to the ground, etc.
The most typical are two cases of closing the current circuit through the human body: when a person touches two wires at the same time and when he touches only one wire. With regard to AC networks, the first circuit is usually called two-phase touch, and the second - single-phase.
A two-phase touch is more dangerous, since the highest voltage in this network is applied to the human body - linear, and therefore more current will flow through the person.
A single-phase contact occurs many times more often than a two-phase one, but it is less dangerous, since the voltage under which a person finds himself does not exceed the phase voltage, i.e. less than linear by 1.73 times.
The main causes of electric shock:
1) Accidental contact with live parts under voltage as a result of: erroneous actions during work; malfunctions of protective equipment with which the victim touched current-carrying parts, etc.
2) The appearance of voltage on the metal structural parts of electrical equipment as a result of: damage to the insulation of current-carrying parts; network phase closure to ground; falling wire (under voltage) on the structural parts of electrical equipment, etc.
3) The appearance of voltage on disconnected current-carrying parts as a result of: erroneous switching on of a disconnected installation; short circuits between disconnected and energized live parts; lightning discharge into an electrical installation, etc.
4) Occurrence of step voltage on the plot of land where the person is, as a result of: phase short circuit to the ground; removal of the potential by an extended conductive object (pipeline, railway rails); malfunctions in the protective earthing device, etc.
The step voltage is the voltage between the points of the earth, due to the spreading of the fault current to the ground while touching them with the feet of a person.
If a person is in a current spreading zone, for example, if an overhead power line is damaged, or if the insulation of a power cable laid in the ground is broken, or if current drains through the ground electrode and stands on the surface of the earth, which has different potentials in places where the feet are located legs, then voltage arises at the step length U w \u003d φ x ─ φ x + 8, where φ x and φ x + 8, are the potentials of the location of the points of the legs; S = 0.8 m - step length.
The electric current flowing through the human body in this case depends on the value of the earth fault current, the resistance of the base of the floor and shoes, and also on the location of the feet.
The step voltage can be zero if both legs of a person are on an equipotential line, i.e. electric field lines with the same potential. Stress in the step can be reduced to a minimum by bringing the soles of the feet together. The greatest electrical potential will be at the point of contact of the conductor with the ground. As you move away from this place, the potential of the ground surface decreases, and at a distance of approximately 20 m, it can be taken equal to zero.
The step voltage is always less than the touch voltage. In addition, current flow through the lower leg-leg loop is less dangerous than through the arm-leg path. However, in practice, there are many cases of people being injured when exposed to step voltage. The defeat during step voltage is aggravated by the fact that due to convulsive contractions of the muscles of the legs, a person can fall, after which the current circuit closes on the body through the vital organs. In addition, the growth of a person causes a large difference in potentials applied to his body.
The main causes of electric shock to a person are:
Electric shock when using faulty household electrical appliances;
Connection to non-insulated parts of the electrical installation (contacts, wires, clamps, etc.);
Mistakenly applied voltage to the workplace;
The appearance of voltage on the body of the equipment, which under normal conditions is not energized;
Electric shock of a faulty power line (approaching a faulty power line at an unacceptable distance);
Classification of electric shocks. Consequences of electric shock.
Electric shocks according to the severity can be conditionally divided into several groups:
Electric shock without loss of consciousness, without violation of breathing and cardiac activity;
Electric shock, characterized by loss of consciousness, while breathing and heart activity are not disturbed;
An electric shock, in which a person loses consciousness, in addition, breathing and heart activity are disturbed;
Electric shock;
State of clinical death.
If a person has impaired cardiac activity and breathing, then it is necessary to immediately carry out resuscitation measures: artificial respiration (one of the methods: mouth to nose or mouth to mouth) and direct heart massage.
Electrical shock may result from electric shock. Electric shock is a severe, reflex reaction of the human body to electric shock. In this case, the person affected by the electric shock must be immediately taken to the nearest medical facility. The victim must be under the constant supervision of medical personnel, since the state of shock can last from one hour to a day. After this time, recovery of the victim or biological death may occur.
Methods and means of protection against electric shock
To protect against electric shock when touching parts of electrical equipment that are not normally energized, but which may become energized if the insulation is damaged or for other reasons, apply:
Insulating materials (rubber gloves, galoshes, rugs...),
grounding,
zeroing,
Safety shutdown...
Insulating agents are commonly used during the repair and maintenance of electrical installations and are not covered in this manual.
grounding
Grounding any part of an electrical installation or other installation is the intentional electrical connection of this part with a grounding device (ground electrode).
This connection is made with a conductor, which is called grounding.
The illustration below shows grounding: the computer case is connected to a grounding conductor (rail):
The grounding conductor is connected to a grounding conductor having a direct connection to the ground. If a phase is accidentally connected to an electrical equipment case, a short circuit will occur and the fuses will trip. Consequently, the electrical circuit will be de-energized and the danger of electric shock will disappear.
The illustration below shows what can happen when a phase is shorted to the case if there is neither grounding nor zeroing.
Zeroing
Protective zeroing of any part of an electrical installation or other installation is an intentional electrical connection of this part with a conductor, which is called a neutral, or zero protective conductor.
If a phase is accidentally connected to an electrical equipment case, a short circuit will occur and the fuses will trip. Therefore, in this case, the electrical circuit will be de-energized and the danger of electric shock will disappear.
Single-phase networks, made according to modern standards, are equipped with three-pin sockets, to which three conductors are connected:
Null,
Zeroing.
This neutral conductor is connected to the solidly grounded zero point (neutral) of the transformer in AC networks and to the solidly grounded midpoint of the power supply source in three-wire DC networks.
In the above illustration, the computer case is connected to the grounding contact of the socket:
Safety shutdown
A protective shutdown is a protection system that provides automatic shutdown by a high-speed device of all phases of the emergency section with a total shutdown time from the moment a single-phase short circuit occurs, no more than 0.2 s.
In other words, a safety shutdown is like a fast-acting fuse that blows when there is a danger of electric shock.
58) Classification of premises for electrical safety
The current rules for the installation of electrical installations (PUE) all premises are divided into the following three classes:
I. Premises without increased danger: dry, with normal air temperature, with non-conductive floors.
II. Premises with increased danger: damp with relative air humidity (long-term) more than 75%; hot with air temperature exceeding +30°C for a long time; with floors made of conductive materials; with a large amount of emitted conductive technological dust deposited on the wires and penetrating inside electrical installations; with the placement of electrical installations with metal cases connected to the ground, metal structures of buildings and technological equipment, allowing simultaneous contact with them.
III. Particularly dangerous premises: especially damp with relative air humidity close to 100%, chemically active environment, simultaneous presence of two or more conditions characteristic of premises with increased danger.
One of the measures to ensure electrical safety in rooms of II and III classes is the use of low voltage current.
As examples of the division of premises according to the degree of danger, the following can be cited: class I includes office premises and laboratories with precision instruments, assembly shops of instrument factories, watch factories, etc.; to class II - storage unheated premises, stairwells with conductive floors, etc.; to class III - all workshops of machine-building plants: galvanic, storage batteries, etc. They also include areas of work on the ground in the open and under a canopy.
59) Providing first aid to the victim from the action of electric current
If you have witnessed that a person has become energized, first of all, you need to free the victim from the action of electric current as soon as possible, especially if the person is holding a bare wire with his hand and is not able to independently break contact with the electrical installation.
The severity of electric shock directly depends on the duration of the current on the body. To do this, it is necessary to turn off the electrical installation with devices specially designed for this (switches, knife switches, removing fuses).
If there is no possibility of a quick shutdown, it is necessary, using improvised means, to create conditions for a quick shutdown of the electrical installation section with the victim. These can be attacks on overhead lines, interrupting a cable or electrical wiring with an ax, removing fuses with a dry rag, etc.
1. When providing first aid in electrical installations up to 1000V, it is allowed to use improvised means that do not conduct electricity (dry board, stick, rope) to separate the victim from live parts. It is possible to pull the victim by the clothes.
2. In electrical installations above 1000V to provide first aid to the victim, it is necessary to use protective equipment, use dielectric gloves and boots, using insulating rods.
In this case, you must follow the rules of your own safety, the person who provides assistance must ensure that he himself does not come into contact with live parts.
2) assessment of the victim's condition.
After the victim is released from the impact of the traumatic factor, it is necessary to assess his physical condition. When assessing the condition, it is necessary to pay attention to the following main signs:
Consciousness: normal, impaired (inhibited or excited), absent;
Respiration: normal, disturbed (wheezing), absent;
Pulse (determined on the carotid arteries): normal (determined well), disturbed, absent.
3) determination of the nature of the injury that poses the greatest threat to the life of the victim.
That is, if a person is unconscious and other characteristic injuries are also visually visible (a broken arm, bleeding, etc.), then first of all it is necessary to proceed with measures that allow the victim to return to consciousness.
4) carrying out the necessary measures to save the victim.
The absence or presence of consciousness is determined visually.
If the victim is unconscious, it is necessary to control his breathing, if breathing is disturbed due to the retraction of the tongue, it is necessary to push the lower jaw forward. Bring the victim back to consciousness by giving him a sniff of ammonia or splashing his face with cold water.
If the victim is in an unconscious state, his pulse is not determined and there is no breathing, you need to start restoring the vital functions of the body by performing artificial respiration and external heart massage.
Artificial respiration is performed if the victim is not breathing on his own, or when breathing is infrequent and convulsive.
5) maintaining the vital functions of the victim until the arrival of the medical staff.
Even if the victim does not show any signs of life (breathing, pulse), he cannot be considered dead, but it is necessary to continue to provide resuscitation until the arrival of qualified medical personnel.
6) call the medical staff or independently organize the transportation of the victim to a medical institution.
The causes of electrical accidents are many and varied. The main ones are:
1) accidental contact with open live parts under voltage. This can occur, for example, during the production of 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 the shoulder, which can accidentally touch uninsulated electrical wires located at an accessible height in this case;
2) the appearance of voltage on the metal parts of electrical equipment (housings, casings, fences, etc.), which are not energized under normal conditions. Most often, this can occur due to damage to the insulation of cables, wires or windings of electrical machines and apparatus, which, as a rule, leads to a short circuit to the case;
3) an electric arc that can form in electrical installations with a voltage of more than 1000 V between a live part and a person, provided that the person is in close proximity to the live parts;
4) the occurrence of a step voltage on the earth's surface when the wire is shorted to the ground or when current drains from the ground electrode into the ground (in the event of a breakdown to 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 for a lack of voltage and a malfunction of the grounding device, etc.
The main measures to eliminate the causes of electric shock discussed above and ensure the protection of operating personnel are:
* Ensuring the inadmissibility of current-carrying parts under voltage for accidental contact. For this purpose, current-carrying 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, application of undervoltage, double isolation, etc.;
* the use of special protective equipment - portable devices and devices, personal protective equipment;
* clear organization of safe operation of electrical installations.
End of work -
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Life safety
Ministry of Education and Science of the Russian Federation. Federal State Budgetary Educational Institution of Higher Professional Education Samara State Aerospace..
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Sprinkler and deluge installations are used to automatically extinguish fires with water. The sprinkler installation consists of devices that supply water, main and
Foam extinguishing
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, hand-held chemical foam fire extinguishers of the OHP-10 type are widely used (Figure 2). In the body of the fire extinguisher there is an 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 a fire with carbon dioxide
Carbon dioxide is used to extinguish flammable and combustible liquids, solids, electrical installations under voltage. Carbon dioxide does not spoil the substances in contact with it,
Fire extinguishing with halogenated hydrocarbons
Currently, highly effective compounds based on halogenated hydrocarbons, such as tetrafluorodibromomethane (freon 13B and 114B2), these bromide
Extinguishing fire with powder compounds
Powder formulations are designed to extinguish fires of flammable liquids and combustible liquids, alkali and alkaline earth metals and their carbides, electrical installations under voltage, and valuable items (archives, museums
Fire communication and alarm
The fastest and most reliable way to notify a fire is an electrical fire alarm (EPS). EPS consists of the following main parts: detectors installed
Labor protection legislation
The main legislative documents in this industry to date are the "Basic legislation on labor protection" and the Labor Code of the Russian Federation. For this industry
Principles, methods and means of ensuring security
In the structure of the general theory of security, a certain hierarchy of principles, methods and means of ensuring security has developed. A principle is an idea, a thought, a fundamental position.
Analysis of occupational injuries
When analyzing the causes that led to the accident, the following methods are used Statistical method, in which statistical data are processed for
Standardization in the field of BD
A special place among the normative documents in the field of labor safety is occupied by the system of labor safety standards - SSBT, the structure of which is shown in Fig. 2. A special role belongs
Building codes and regulations (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 employees with instructions on labor protection. This work should be carried out
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 the funds for the payment of assistance for temporary disability. · Annual savings from reduced injury rates · Payroll savings in
