Dangerous for life is the voltage of over 50 V, and under adverse conditions - 12 V (humidity, etc.). Dangerous current of 0.05a (50 mA). The degree of damage is influenced electrical resistance A person, a contact area, a gene of current, its frequency, the path of leakage, the duration of exposure, as well as the humidity of the air, the condition of the skin and well-being.
Means of electrical protection on rolling stock and requirements for them.
These include: dielectric gloves, pincers with isolated sponges, short. All of them must have a stamp instrumental and stamp indicating the shelf life and allowable voltage.
Big Must have a stamp tool depot and numbering assigned to this composition. A flexible cable, a cross section of at least 16-25 mm 2, should be well irradiated and soldered at the ends. Clamp screws must freely walk on the thread. It is allowed to break no more than 5% of the flexible cable.
Before use dielectric gloves It is necessary to clean them from dirt and dust, check on the absence of punctures by twisting to the side of the fingers, check on the stampe if the periodic test period is not expired. The replacement of gloves should be made a few days before the regular test specified on the dad. This is due to the fact that some compounds remain overnight on the line, while there is no possibility of replacing gloves. It is forbidden to use gloves with external damage, punctures or expired periodic tests.
When using gloves, they must be worn over the sleeves, without leading. Their length should be at least 35 cm. The dielectric gloves are tested 1 time in 6 months with a voltage of 6 kV for 1 minute (produced in the laboratory of electrogenation of the power supply service).
In gloves should be made: replacement of fuses WCVN, lamps of red headlights, installation and rotation of the reversing handle in Crubber and Spin formulation.
Pliers with isolated sponges inspecting visually with the inspection of their performance.
Ticket number 1.
1. The distribution area of \u200b\u200bsafety regulations during the operation of electrical installations
The safety rules for the operation of electrical installations apply to employees of organizations, regardless of the forms of ownership and organizational and legal forms engaged in the maintenance of electrical installations that perform settub, repair work, testing and measurement.
The rules apply only to the current electrical installations.
Parts of electrical installations subject to grounding, grounding
To parts to be grounded or reducing include:
Cases of electrical machines, transformers, devices, lamps, etc.;
Drives electrical apparatuses;
Secondary windings of measuring transformers;
Switchboards, shields and control cabinets;
Metal shells of power cables, steel tubes Wiring and others metal constructionsassociated with the installation of electrical equipment;
Metal housings of mobile and portable electrical receivers.
Setting grounding
1 Set the grounding to the current-host parts is necessary immediately after checking the absence of voltage.
2 Portable grounding You first need to attach to a grounding device, and then, after checking the absence of voltage, set to the current parts.
It is necessary to remove the portable ground in reverse order: first remove it from the current-handing parts, and then disconnect from the grounding device.
3 Installation and removal of portable grounds in electrical installations The voltage above 1000V must be performed in dielectric gloves using an insulating rod. Fasten the clamps of portable grounds follows the same barbell or directly with their hands in dielectric gloves.
4 It is not allowed to use the conductor not intended for this purpose.
Requirements for the table for commissioning
Must be performed from a toxconducting material (wood, plastic, etc.).
There must be shelves for the placement of control and measuring equipment and power sources;
It must be equipped with a separate electrical folder with a common switch, fuses, a signal lamp or a voltmeter, recessed plug sockets and protective grounding;
It is strictly forbidden to make a metal edging of the working surface of the table made of dielectric material, to exclude a touch voltage in the case of a breakdown of isolation or malfunction of grounding conductors (opening more than 5%, poor contact).
What should know and be able to assist the victim.
Must know:
The main signs of violation of the vital functions of the human body;
General principles for first aid and its techniques in relation to the nature of the injured injury obtained;
Basic ways to carry and evacuating victims.
Should be able to:
Evaluate the status of the victim;
Determine the sequence of first aid;
Perform artificial respiration and indirect heart massage;
Stop bleeding by imposing a harness, gulling bandage, pressed blood vessels;
Impose a bandage when injured, burn, injury;
Immobilize (create peace) damaged part of the body;
Provide assistance in thermal, sunlight, etc.
Ticket number 2.
What electrical installations are called applicable.
The current electrical installations are considered to be such installations that contain electricity sources (chemical, electroplating and semiconductor elements), which are in a voltage completely or partially, or to which at any time can be supplied with the inclusion of switching equipment.
Current and voltage values, life-threatening. Step tension.
The magnitude of the current dangerous for a person is 50 mA and more.
The value of the current, deadly for humans - 0.1 A.
The value of alternating voltage is 50 V and more.
The value of constant voltage is 120V and more.
Stepleg It is called the voltage between the two points on the surface of the earth, at a distance of 1 meter one from another, which is taken equal to the length of the person's step. It is determined by spreading the electric current over the surface of the Earth or a conductive floor in the case of a single-phase closure on the Earth of the wire. The magnitude of this voltage depends on the width of the step, the resistivity of the soil and the location of the person (the closer the person stands to the location of the closure, the greater the magnitude of the voltage). The wider step, the greater the current proceeds along the path of the foot.
When hitting under step voltage, convulsive involuntary muscle contractions arise and, as a result, a drop in man to the ground. The current begins to pass along a new way, more dangerous (for example, a leg), which is fraught with fatal outcome.
For protection against step stress, additional protection means are the dielectric bots, rugs. In the case when the use of these funds is not possible, you should leave the danger zone by the "goose step" - the heel of the walking legs, without breaking away from the Earth, is attached to the sock of another leg.
It is also safe to move on a dry chalkboard and other not conductive subjects, subjects.
If the victim himself can not leave the danger zone, it follows him
remove, isolating the foot of the legs, the boot using rubber boots, woolen dry tissue, etc.
ELECTRICAL SAFETY
Danger of current for man.
The effects of electric current on the human body can cause lesions, the outcome of which depends on current values \u200b\u200band duration of its actionas well as from frequency and path passing through the human body and the individual properties of the body.
The danger of exposure to the electric current on a person is also more because it is not noticeable for an eye, not hearing, not felt at a distance, there is no smell, but perceived only at the time of contact with unprotected campsive wires or parts of electrical installations and their buildings that for what - Loil caused the reasons for tension.
The human body, which turned out to be under the action of an electric current cannot only be considered as a physical body. Electrotok, enrolling through the place of "entrance" to the human body, has an irritant effect throughout the passage of current, and not only in the fields of its "login" or "exit". This is the feature of the current action compared with other stimuli (mechanical, thermal, etc.), which causes only local irritation (at the entrance).
The effect of electrotock on the human body can be thermal (burn), mechanical (tissue rupture) or chemical (electrolysis). Current can also have a biological impact, causing contraction of muscles, palsy of breathing, paralysis of the heart.
Permissible current and voltage
Main factorsaffecting the outcome of man damage electric shock - this is the magnitude of the currentpassing through man and the duration of its impact.
The alternating current of the industrial frequency of 50-60 Hz is stronger than the person than the constant current of the same value.
Value alternating currentat which a person is difficult to tear away from the electrodes 12-15 Ma - It is considered dangerous to human life.
For a safe amount for AC purity 50-60 Hz accepted 10 mA.For direct current – 50 Ma.
The person begins to feel the impact passing through the current of the short value:
0
Threshold tangible current
, 6-1.5 mA - with alternating current
5 - 7 mA - with constant current.
Large currents cause muscle convulsions and unpleasant painful sensations, which increase with increasing current and apply to all major parts of the body.
Thresholding unrequisite Toki.
With toke 3-5 Ma and frequency of 50 Hz irritant effect of the current is felt by the entire brush hand. For 8-10 Ma The pain is sharply enhanced and covers the entire hand, accompanying involuntary convulsive cuts of the muscles of the hand and forearm. For 10-15 Ma The pain becomes unbearable, and the cramps of the muscles of the hands as significant that a person is unable to overcome them. At the same time, it cannot break the hand in which the current-carrying part is held.
Current variables 10-15 mA at \u003d 50 Hz
Permanent currents 50-80 mA
A variable current of 25-50 mA - affects the muscles of the arms and the body, on the muscles of the chest, breathing is greatly hampered. The prolonged impact of this current can cause a breath termination, after which, after some time, death comes from choking. The same impact on the lungs, but more quickly has an alternating current of 50-100 mA. At the same time, the work of the heart is disturbed. However, the first time stops the work of the lungs, and then the heart.
P
Threshold fibrillation Toki.
Eramed currents 100 mA - 5 A
Permanent currents of 300 mA - 5 a
These currents distribute their irritating effect on the heart muscle. This circumstance is very dangerous to human life, how many 1-2 seconds after the circuit of the circuit of this current through a person can adopt the heart fibrillation. As a result, blood circulation is stopped and a lack of oxygen arises in the body, which leads to a respiratory stop, i.e. death.
The current is greater than 5 and the fibrillation of the heart does not cause, an immediate stopping of the heart occurs (bypassing the state of fibrillation), as well as palsy of breathing. If the current is short-term (up to 1-2 second) and does not cause damage to the heart (as a result of heating, burn, etc.), then after turning off the current, the heart resumes normal operation independently, and the breathing is not restored, immediately needed Help the victim in the form of artificial respiration.
Duration of passage The current through the body significantly affects the outcome of the lesion: the longer the current effect, the greater the likelihood of severe or deadly outcome. This is due to the fact that with an increase in the time of exposure to the current tissue, the value of this current increases (by reducing the resistance of the body) and grow (accumulated) the consequences of the current effect on the body and increases the probability of coincidence of the moment of passage through the heart with a vulnerable phase for current T - 0.2 sec. Cardiac cycle (cardiocycle). What time of current flow can be considered safe for the human body?
Can be taken to calculate and evaluate protective measures that permissible interval of the existence electrical chain Through the body of man ranges from 0.01 to 2 seconds.
Evaluity is important for the outcome of the defeat. Current through the human body. It has been established that the tissues of different parts of the human body have different specific resistances. When current passes through the human body, the largest part of the current passes along the path of the smallest resistance, mainly along the blood and lymphatic vessels. The most dangerous is top Path Along the body, for example: Hand - legs or through the heart, head, spinal cord. However, deadly lesions are known when the current passed along the path of the harbor or hand - hand.
Analysis of electrical exchanging shows that the total current passes along the way hand hand Through the heart - 3.3%, left hand - legs through the heart - 3.7%, head - hands - 7%, head - legs - 6.8%, legs through the heart - 0.4%, right hand - Legs through the heart - 6.7%.
Contrary to the established opinion the greatest value of the current through the heart is not on the way left hand - legs, and along the way right hand - legs. This is explained by the fact that most of the current enters the heart along the longitudinal axis lying along the way the right hand - legs.
As a result of analyzes of electrotramatism cases, it was established that one of the most important biological factors that determine the outcome of the electric shock is a factor attention.
If the electrical installation under voltage is carefully referred to the operations performed and constantly remembers the possible consequences of its negligence, then its concentration and intense attention is in a state not only to weaken the effect of electrotock, but sometimes even destroy. If an electric blow - during the period of intense attention of the working, then its action will be much weaker than at the time of an unexpected strike.
Human body resistance
The upper horny layer of human skin with a thickness of 0.05 - 0.2 mm, not having blood vessels and nerves, is called epidermum. Epiderma can be considered as a dielectric.
The overall electrical resistance of the human body depends on the size of the resistance of the top layer of the skin and its status. Human skin resistance depends on the following main factors:
Skin condition (clean, dirty, wet, dry, whole, damaged);
The magnitudes of the surface of the touch of electrodes and the density of the contact;
Values \u200b\u200band kind of electrotock and applied voltage;
Frequency current;
Duration of passage;
The overall state of the nervous system.
The skin resistance is the less, the greater the surface of contact with the electrodes. If the surface of the touch is more than 150 cm2, then RR drops to 600 ohms. The human body resistance drops with increasing current, as it increases the heating of the top layer of the skin and sweating in the field of skin contact with the electrodes. In calculations on TB RR is taken equal to 1000 ohms. With an increase in current Full resistance RR decreases. A significant reduction in resistance is observed only at low voltages of 20-40 V, which do not cause a breakdown of the skin.
At voltages 100B and above, the increasing frequency does not cause a noticeable decrease in RR (which in these conditions is approaching 600 ohms). Currents with a frequency of 200 and 500 Hz are no less dangerous than currents with a frequency of 50 Hz. The danger of the current action on the living organism is noticeably reduced at a frequency of 1000 Hz and above. The currents of the high frequency, ranging from the hundredth kHz, cause only burns, not affecting the internal organs of a person. It is explained by the fact that such currents are not able to cause the excitation of nerve and muscle tissues. When exposed to DC, RR is always higher than when alternating current. It is proved that the danger of the value of the current is determined depending on the voltage value. So at a voltage of up to 450V, an alternating current is a greater danger, and at a voltage of 450-500V, alternating and constant currents are equally dangerous; At voltage above 500V, constant current is most dangerous. In the frequency range of 50-500 Hz, the danger of exposure to direct and alternating current is approximately the same.
Permissible safe voltages.
Analysis of accidents shows that the greatest number of electricians occurs as a result of a random touch to naked, unprotected parts of EU under voltage.
Depending on the operation of the EU and the surrounding production medium, three safe voltages of an alternating current of industrial frequency (50-60 Hz) are installed.
Indoors without increased danger - 65V.
Indoors with increased danger - 36V..
Indoors of particularly dangerous - 12V.
The most commonly defeated by electric workers, who, by nature, they deal with EU voltage up to 1000V, because They unreasonably neglect protective means, considering this stress non-dangerous. Relatively safe voltage is considered U.up to 36V.. U \u003d 36 to 60V causes burns and painful skin irritation.
U \u003d 60V to 100V is the boundary of serious danger and causes significant burns and palsy of breathing and heart. Electrotok voltage above 100V is considered dangerous to human life.
When designing equipment, devices and EUs, special protection measures are provided to randomly touch service personnel to current, unprotected wires or to the body of the device that has occurred under voltage short closure or other fault.
Classification of industrial premises
By the degree of danger of defeating employees with electricity, industrial premises are divided into three categories.
but) conductive floors (reinforced concrete, brick, earthy, etc.);
b) conductive dust or damp (with relative humidity, longer than 75%;
c) Temperature for a long time exceeding 30 0 C.
d) the possibilities of simultaneously touching a person to grounded metal structures (buildings, technological apparatus, mechanisms) on the one hand and to metal electrical equipment housings on the other.
a) special damp (with relative humidity close to 100%);
b) a chemically active medium (vapor acting destroyably on the insulation of current-carrying parts of the equipment);
c) at least two conditions for premises with increased danger.
Chief Engineers (Technical Officers) are required to determine the degree of danger of all industrial premises and attribute them to the specified categories with the registration of the order of the enterprise.
The danger of injuries for a person from electric shock, both in production and in everyday life. It is a direct consequence of non-compliance with security measures, as well as refusal or malfunctions of electrical equipment and household appliances. Therefore, the use for our household needs to overestimately overestimate. In today's article, we will consider the practice and the main possibilities of using a secure voltage for a person in our house, dacha or apartment.
What is electric, securely voltage?
Now the voltage of the 42 volt electric network is considered safe for a person (until recently - it was 36 V), used for portable lighting and household appliances in air and in the house and 12 volts, provided that portable lamps and appliances inside boilers, metal tanks, etc. .
The permissible current for a person is considered to be the current strength at which it can independently free from its impact. The maximum permissible value of the current passing through the human body depends on its exposure time. For the variable current, with its frequency of 50 Hz, permissible according to GOST1.1.038-82 is only 2 V, and the current is only 0.3 mA. For direct current - the permissible tension voltage of only 8B, with a current of 1.0 mA (data is given for exposure time less than 10 minutes per day).
Safety levels of voltage voltage in the house are obtained from ours using ours, while using lowering transformers, or directly - using the rechargeable battery with a rated voltage of 12 and 24 volts.
Small voltages and nuances of their use in everyday life.
Power sources of low-voltage electrical networks are reduced transformers operating from conventional household electrical networks with a voltage of 220 V, as well as 12 or 24 volt batteries. Secondary windings of lowering transformers must necessarily be based on, and connect to the grounding indoor circuit, installation or electrical equipment.
Low-voltage electricity of the net Voltage up to 42 to advisable, and sometimes it is necessary to use in the following cases:
When suspension of lighting devices with incandescent lamps at an altitude of less than 2.5 m, which are in rooms with increased danger or especially dangerous rooms.
In electrical installations, in order to reduce the risk of human damage to electric shock.
To power the power tools used to work in rooms with increased hazard.
For powering power tools used to work in particularly dangerous rooms with mandatory use of dielectric mats, galoshes and gloves.
As a power supply of landscape lighting country house Or cottages, with low-voltage, since this system is now the most fully meets all the current requirements of external lighting.
To power the ultra-low secure voltage system in the bathroom by installing a lower separation transformer with its grounding on the low-voltage side.
Checking the knowledge of the rules. Types of checks. The frequency of inspections
Checking knowledge of workers is divided into primary and periodic (regular and extraordinary). Primary knowledge check is carried out by workers who first enrolled in the service associated with the maintenance of electrical installations, or during the interruption in the test of knowledge for more than 3 years; the next one - in the manner prescribed in paragraph 1.4.20; And extraordinary - in the manner pressed in paragraph 1.4.23.
Another check should be made on the following dates:
- for electrical personnel, directly organizing and conducting operational maintenance of existing electrical installations or commissioning, electrical installation, repair work or preventive tests, as well as for personnel with the right to issue outfits, orders, operational negotiations - 1 time per year;
- For administrative and technical personnel, not related to the previous group, as well as for labor protection specialists, admitted to inspection of electrical installations - 1 time in 3 years.
The next check time is set in accordance with the date of the last test of knowledge.
Employees who received in the next test of knowledge unsatisfactory assessment, the Commission appoints a re-verification no later than 1 month from the date of the last check. The certificate validity period for the employee who received an unsatisfactory assessment is automatically extended to the period appointed by the Commission for the second inspection, if there is no knowledge verification of the Special Decision of the Commission on the temporary removal of the employee from work in electrical installations.
An extraordinary knowledge check is carried out regardless of the period of the previous check:
- when entering the consumer with new or recycled rules and rules;
- when installing new equipment, reconstruction or changing the main electrical and technological schemes;
- when appointing or translating to another job, if new duties require additional knowledge of the norms and rules;
- in violation by employees, the requirements of regulatory acts on labor protection;
- at the request of state supervision;
- on the conclusion of commissions investigating accidents with people or violations in the energy facility;
- when improving knowledge to a higher group;
- when checking knowledge after receiving unsatisfactory evaluation;
- When breaking in this position for more than 6 months.
Question 2. When you need to turn off the electric motor immediately
The electric motor must be immediately (emergency) disconnected from the network in the following cases:
1) in cases of accidents with people;
2) when smoke and fire appears from the electric motor, as well as from its streaming hardware and excitation devices;
3) breakage of the drive mechanism, the appearance of an abnormal knock;
4) a sharp increase in the vibration of the bearings of the unit;
5) Heating bearing over the permissible temperature set in the manufacturer's factory instructions.
Question 3. What voltage is considered dangerous for a person
With respect to the magnitude of the "permissible" or "safe" voltage, there is still no steady point of view, since the electrical resistance of a person varies widely depending on the specific conditions. Therefore, various countries regulate their norms. For example, in France, 24V is received for AC and 50B for DC. Our practice, depending on the surrounding conditions, takes over a permissible voltage to 50V AC. However, these voltages cannot be considered as ensuring complete safety. For example, in the literature, cases of deadly damage to a person with a voltage of 12V and below are described.
An dangerous amount of current flowing through the human body should be considered 10 mA, deadly - 100 mA.
