Business game number 8.
Providing first to medical care when damaged by electric shock.
Theoretical knowledge necessary to fulfill the business game number 8.
Electric current action on human body. Types of electric shock.
The widespread use of electricity in all sectors of the national economy increases the number of people who exploit electrical equipment. Therefore, the problem of electrical safety during the operation of electrical equipment becomes of particular importance.
Analysis of industrial accidents indicates that the number of injuries caused by the action of electricity is relatively small and is 0.5-1% of the total accidents. However, it should be noted that from the total amount of fatal accidents at the production of 20-40%, it happens due to the error defeat, which is more than due to the action of other reasons, and about 80% of death lesions electric shock occurs in electrical installation voltage up to 1000 B.. Significantly distributed such electrical installations, and almost all persons who work in the industry are serviced, and electrical installations with tension more than 1000 B. servicing small highly qualified personnel.
Electrotramma - This is an injury caused by an electrical current or electric arc.
Electricians are divided into two types :
Elertowers that occur when current passes through the body of the century,
Electricalravum, the appearance of which is not related to the passage of the current through the human body. The defeat of a person in this case is associated with burns, blinding electric arc, fall, and as a result - significant mechanical damage.
Types of electrotock effects per person:
- Thermal effect of current
Burns of individual parts of the body,
Heating to a high temperature of blood vessels, nerves, hearts, brain and other organs, which are on the path of the current that causes substantial functional disorders into them.
- Electrolytic effect of current It is characterized by the decay of organic fluid, including blood, which is accompanied by significant changes in their physicochemical composition.
- Mechanical (dynamic) action - This is a bundle, gaps and other similar damage to the body tissues, including the muscles, the walls of blood vessels, the vessels of the pulmonary tissue due to the electrodynamic effect, as well as the instantaneous explosive formation of steam from overheating of fluid and blood.
- Biological effects of current it is manifested by irritating and excitement of live tissues of the body, as well as due to the violation of the internal biological processes occurring in the body that are closely related to its life functions.
Types of electrical injuries:
Local electricians that cause local damage to the body;
General electricians (electric shocks) when amazed (or arises the threat of lesion) the entire body due to the violation of the normal activity of vital organs and systems.
Ø Local electrician - A pronounced violation of the integrity of body tissues, including bones caused by the influence of electric current or electric arc. Most often is the surface of damage, that is, skin damage, and sometimes other soft ligaments and bones. Local electricians are cured and the performance of the victim is restored in whole or in part. However, in severe burns, a person dies. In this case, the immediate cause of death is not an electric current, but local damage to the body caused by the current. Characteristic local electricians:
Ø electric burns, It is damage to the body surface with the effect of electric arc or high currents that pass through the human body.
Ø electrical signs, this is a clear label A diameter of 1-5 mm gray or pale yellow, which appears on the surface of the skin of a person at the passage of current. In most cases, electrical signs are painless (the top layer of the skin is coming down, and the affected place acquires the initial color, the plasticity and sensitivity is restored).
Ø Electrometalization - penetration of metal particles due to its spraying and evaporation under the action of current. It can occur with short circuits, disconnects of voltage by disconnectors and switches under load. In this case, small particles of the molten metal under the influence of dynamic forces and heat flux are spilled in all directions at high speed. Each of these particles has a high temperature at a low heat reserve, and therefore it is not capable of burning clothes. Therefore, open parts of the body are affected: hands and face. When eye damage, treatment may be long and difficult, and in some cases the victim can lose sight. Therefore, work in which the occurrence of an electric arc possible should be performed in protective glasses.
Ø Mechanical damage They are in most cases a consequence of sharp convulsive muscle contractions under the influence of the current that passes through the human body. As a result, tendons, skin, blood vessels and nervous tissue can occur, and even bone fractures. Mechanical damage occurs when operating in installations with voltage up to 1000 V with long-term finding of a person under voltage.
Ø Electrophthalmia - This is the inflammation of the outer shells of the eye, which occurs under the influence of a powerful stream of ultraviolet rays. Such irradiation is possible in the formation of an electric arc (with a short circuit).
Electrophthalmia is developing 4-8 hours after ultraviolet irradiation. At the same time, there is a place of redness and inflammation of the skin, the mucous membranes of the eyelids, tears, purulent separation from the eyes, the seizures of the eyelids and partial loss of vision. The victim feels a headache and a sharp pain in the eyes, which is enhanced in the world. The prevention of electrical phthalmia when servicing electrical installations is provided by using protective glasses with conventional glass, which almost do not miss ultraviolet rays, and simultaneously protect the eyes from infrared irradiation and splashes of molten metal.
Ø Electric Strike - this is the excitation of alive tissues of the body by electric current, which is accompanied by a convulsive muscle contraction. Such a blow can lead to a violation and even the complete cessation of the work of the lungs and the heart. At the same time external local damage, that is, electrical injuries, a person may not have.
Depending on the severity of the lesion electric blows can be conditional divided by 5 degrees:
I - convulsive barely tangible muscle contractions;
II - convulsive cuts of muscles that accompany the strong barely tolerable pain without losing consciousness;
III - convulsive muscle contraction with loss of consciousness, while maintaining breathing and heart work;
IV - loss of consciousness and violation of cardiac activity or breath
V is clinical death, that is, the stop of the heart and lungs.
Approximately 75% of cases of lesion of people current is accompanied by the emergence of local electric products.
2. Causes of dead out of electric current .
The causes of death from electric current can be :
Stopped the work of the heart,
Stop breathing
Electric shock.
The simultaneous action of two or even three of these reasons.
The cessation of cardiac activity from electric current is most dangerous, since to return the victim to life in this case is, as a rule, a more complex task than when stopping the breath or with a shock.
The effect of current on the heart muscle can be:
Direct when the current passes directly in the region of the heart,
Reflex, that is, through the central nervous system when the current path is outside this area. In both cases, a heart stop or its fibrillation can occur. Under the defeat of the current, the fibrillation of the heart occurs significantly more often than its complete stop.
Fibrillation of the heart - Chaotic high-grade cuts of the heart muscle (fibrils), in which the heart is not able to drive blood along the vessels. My heart fibrillation to step up due to passing through the human body along the path hand-hand, or the hand-legs of alternating current by force of more than 50 mA frequency of 50 Hz for a few seconds.
With heart fibrillation which arises due to short-term current, breathing may still continue 2-3 minutes. Since, together with blood circulation, the body's supply of oxygen ceases, and the person comes a rapid sharp deterioration in general condition and breathing ceases. Fibrigration continues for some time and ends with a complete stop of the heart. Clinical death comes.
Starting breathing This occurs due to the immediate effect of the current on the muscles of the chest, which is involved in the respiratory process. A person begins to feel difficulty breathing due to a convulse reduction of muscles already at a current of 20-25 mA 50 Hz frequency. With a greater value of the current strength, this action is enhanced. In the case of a long passage of current, the person comes asphication - a painful state due to lack of oxygen and excess carbon dioxide in the body. With asphytes, consciousness, sensitivity, reflexes are gradually lost, then breathing ceases, and after some time the heart stops or its fibrillation occurs, that is, clinical death comes.
The cessation of cardiac activity in this case is due not only to the relative influence of the current on the heart, but also the cessation of the body's supply of oxygen, including cells of the heart muscle due to the stop of the respiratory.
Electric shock - a peculiar severe nervous reaction of the body due to electric current irritation, which is accompanied by deep circulation disorders, respiration, metabolism. Shock state continues from several tens of minutes before a day. After that, the death of a person may occur due to the complete fading of vital functions, or recovering - due to timely active medical intervention.
Causes of electricians can be grouped by the following factors. :
1. Touching the current-carrying parts under voltage due to non-compliance with the rules of security, structural defects and installation of electrical equipment;
2. Touching the inadequate parts, which caused themselves under voltage (insulation damage, wire closure);
3. erroneous voltage supply to the installation where people work;
4. Lack of reliable protective agents.
3. First medical care when defeating the human current.
First aid - This is a set of events, aimed at restoring or preserving the health of the victims carried out non-medical workers (mutual assistance) or the victims themselves (self-help).
The most important condition for first aid - its speed . The faster it is rendered, the more hope for a favorable outcome. Deletion and long-term preparation may entail the death of the victim.
Introduction ..................................................................................................
1. The effect of electric current on the human body ................................. ..
2. Factors that determine the outcome of the electric shock ...................
3. Maximum permissible values \u200b\u200bof stresses and currents .............................. ..
4. Scheme, purpose, principle of operation and the scope of the application.
Need to re-ground zero wire ...........................
Conclusion ........................................................................................................
Literature………………………………………………………………………………..
Introduction
In this course work, principles and funds were considered. electrical protection. In particular, the rank. Such questions were also included in the work as:
Electrical current actions on the human body;
Factors determining the outcome of elimination of EL. current;
Permissible levels of tensions and currents;
Scheme, appointment, principle of operation and scope of application;
Solving the problem on the topic "Rangery".
1. Action El. Current on the human body
When operating and repairing electrical equipment and networks, a person may be in the field of action electric field or direct contact with electrical current wiring. As a result of the passage of current through a person, a violation of its livelihoods can occur.
The danger of electric shock is aggravated by the fact that, first of all, the current does not have external signs and as a rule, a person without special devices cannot detect the danger threatening in advance; Secondly, the effects of current per person in most cases leads to serious violations of the most important vital systems, such as central nervous, cardiovascular and respiratory, which increases the severity of the defeat; third, alternating current Created to cause intensive muscle cramps, leading to a non-releasing effect, in which a person cannot be free from the effects of current; In the fourth, the effects of current causes a sharp reaction to the sharpness, and in some cases the loss of consciousness that when working at height can lead to injury as a result of the fall.
Electric current passing through the human body can have biological, thermal, mechanical and chemical actions. The biological effect consists in the ability of the electric current to irritate and excite live tissues of the body, thermal - in the ability to cause body burns, mechanical - lead to tissue rupture, and chemical - to blood electrolysis.
The effect of electric current on the human body may cause an electrician. Electricalrama is an injury caused by the exposure to electric current or electric arc. Conditionally electricians are divided into local and common. With local electricians, local damage to the body arises, expressed in the appearance of electrical burns, electrical signs, in the metallization of the skin, mechanical damage and electrophthalmia (inflammation of the outer shells of the eyes). General electricians, or electric shocks, lead to the defeat of the entire body expressing in violation or complete termination of the activities of the most vital organs and systems - light (breathing), heart (blood circulation).
The nature of the effect of electric current per person and the severity of the damage to the victim depends on many factors.
Evaluate the danger of exposure to electric current per person in responses of the body. With increasing current, three qualitatively excellent responses are clearly manifested. This is primarily a feeling, more convulsive muscle contraction (irritable for alternating current and pain constant) and, finally, physyrillation of the heart. Electrical currents causing the appropriate response are divided into tangible, uncomfortable and fibrillation.
2. Factors determining the outcome of electric shock
The factors affecting the outcome of electric shock are:
1. Current value.
2. Voltage value.
3. Time actions.
4. Rod and current frequency.
5. Crane path.
6. Resistance to man.
7. Environment.
8. Focusing.
2.1. The magnitude of the current
By the magnitude of the current, currents are divided into:
Imperceptible (0.6 - 1.6 m);
Felt (3ma);
Leaving (6mA);
Irremissive (10-15th);
Suffocating (25-50mA);
Fibrillation (100-200mA);
Thermal effects (5a and above).
2.2. Voltage value and 2.3. Time of action
According to GOST 12.1.038-82, the SSBT "Maximum permissible values \u200b\u200bof stresses and currents. Electrical safety". The factors of the voltage and the exposure time of the electric current are shown in Table. one.
Table 1
With short-term exposure (0.1-0.5C), the current of the order of 100 mows does not cause heart fibrillation. If you increase the duration of exposure to 1C, the same current may result in death. With a decrease in the duration of exposure, the value of current values \u200b\u200bis significantly increased. When changing the exposure time from 1 to 0.1C, the allowable current increases 16 times.
In addition, the reduction in the duration of exposure of the electric current reduces the risk of human damage based on some features of the heart. The duration of one period of the cardiocycle (Fig. 2.1.) Is 0075-0.85c.
In each cardiocycle, there is a systole period when the heart ventricles are reduced (QRS peak) and pushed blood into arterial vessels.Phase T corresponds to the end of the reduction of ventricles and they go to a relaxed state. During the diostole, the ventricles are filled with blood. Phase P corresponds to the reduction of atrium. It has been established that the heart is most sensitive to the effects of electric current during the phase T cardiocycle. In order to arise the heart fibrillation, it is necessary for the time of exposure time with the phase T, the duration of which is 0.15-0.2C. With a reduction in the length of exposure to electric current, the likelihood of such coincidence becomes less, and therefore, the risk of heart fibrillation decreases. In case of incomprehension of current time through a person with a phase, Toki, significantly exceeding threshold values, will not cause heart fibrillations.
2.4. Rod and current frequency
Permanent and variable currents various influences On the body mainly at stresses up to 500 V. With such stresses, the degree of damage to the constant current is less than the variable of the same value. Believe that voltage is 120 V direct current Under the same conditions, equivalent to the risk of voltage 40 in the AC industrial frequency. At voltage of 500V and above, differences in the effects of direct and alternating currents are practically not observed.
Studies have shown that industrial frequency currents (50Hz) are the most unfavorable. With increasing frequency (more than 50 Hz), the incommary current increases. With a decrease in frequency (from 50Hz to 0), the inclusive current values \u200b\u200balso increases at a frequency equal to zero (permanent current - pain effect), they become more about three times.
The values \u200b\u200bof the fibrillation current at frequencies of 50-100Hz are equal, with an increase in frequency to 200Hz, this current increases by about 2 times, and at a frequency of 400 Hz - almost 3.5 times.
2.5. Toking pathway
When touched a person to current parts, the current path may be different. In total, there are 18 options for closing the current through a person. The main ones are:
Head - legs;
Hand - hand;
Right hand - legs;
Left hand - legs;
Leg - leg.
The degree of lesion in these cases depends on which human bodies are exposed to current, and on the value of the current passing directly through the heart. So when current flows along the way "Hand - Hand" through the heart passes 3.3% of the total current, along the way "Left Hand - Legs" 3.7%, "Right Hand - Legs" 6.7%, "Leg - Leg" - 0.4%. The magnitude of the incommive current on the path "hand - hand" is about two times less than along the path "Hand - Legs".
2.6. Resistance to man
The magnitude of the current of the human body through any section of the human body depends on the applied voltage (toupe voltage) and the electrical resistance of the current body of the body.
There is a non-linear dependence between the affect and voltage: with increasing voltage, the current is growing faster. This is due mainly by the nonlinearity of the electrical resistance of the human body. On the plot between two electrodes electrical resistance The human bodies mainly consists of the resistance of two thin outer layers of skin relating to the electrodes, and the internal resistance of the rest of the body. A poorly conductive outdoor skin layer adjacent to the electrode, and the inner tissue under the poorly conductive layer, as if form a capacitor, with a capacitance with and resistance to its insulation V H (Fig.2.2.). With increasing current frequency, the human body resistance decreases and at high frequencies almost becomes equal to internal resistance. At voltage on the electrodes 40-45V, there are significant field strengths in the outer layer of the skin, which completely or partially violate the semiconducting properties of this layer. With increasing voltage, the resistance of the body decreases and at a voltage of 100-200V drops to the value of the internal resistance of the body. This resistance for practical calculations can be taken equal to 1000 ohms.
2.7. Environment
humidity and air temperature, landfilled metal structures and floors, conductive dust and other factors ambient An additional effect on the condition of electrical safety is rendered. In wet rooms with high temperatures or external electrical installations, adverse conditions are folded under which the best contact with current-time parts is ensured. The presence of grounded metal structures and floors creates increased danger of lesion as a result of the fact that a person is almost constantly connected with one pole (land) of electrical installation. Conductive dust also improves the conditions for the electrical contact of the person with both the current-friendly parts and the ground.
2.8. Factor influence
The influence factor plays an important role in lesion by electric shock. Figure 2.3. A graph of the dependence of the liberation of students with electric shock is presented if they know that the installation is under voltage.
4. Scheme, purpose, principle of operation and the scope of the application. The need to re-ground zero wire
Release - metal connection of the electrical installation housing with zero wire, allowing to reduce emergency mode to one-phase short closure With the subsequent disconnection of the damaged contour in the minimum short time (0.2С).
The reinforcement is used in four wired networks with a deaf-grounded neutral voltage up to 1000V. The protective effect of the zero is to reduce the duration of the closure on the body and, therefore, in reducing the exposure time of the electric current per person.
The re-ground of the zero wire does not fully protect against damage to the current, but only softens the emergency mode, reduces the voltage on the case 2-3 times. The danger of lesion is preserved, therefore, individual protective equipment (rugs, mittens, etc.) are applied.
Conclusion
In conclusion, it should be noted that the questions set in the task are solved. The work describes the effect of electric current per person, the scheme, purpose, the principle of the reassessment is shown. Nominal currents of fuse inserts were also selected, the maximum permissible resistance of the loop "Phase-zero" loop. Permissible levels of tensions and currents according to GOST 12.1.038-82 are given.
LITERATURE
1. Labor protection at ZH.D. transport. Ed. SOUTH. Sibarova. -M: Transport, 1981.
2. Zimin E.N. Protection asynchronous engines up to 500V. -M. _L.: Energy, 1967.
3. Belyaev A.V. The choice of apparatura, protection and cables in the networks of 0.4 kV l.: Energoatomizdat, 1988.
Chapter 8.
Electrical safety in productionWelding work
8.1. Electric current action on human body
Electric current that has a negative impact on a person belongs to hazardous production factors.
The following types of electric workers are possible:
. Electric burn;
. Electrical signs arising in places of human contact with current-host electrical installations;
. Metalization of the skin is the penetration of the smallest metal particles;
. Electrophthalmia - inflammation of the outer shell;
. Electrical shock - electrician caused by the reaction of the nervous system to irritation by electric shock.
The main causes of electric shock are:
. violation of the rules for the technical operation of electrical installations;
. Touching their current parts;
. Touching metal inactive parts, which caused by voltage due to the malfunction of isolation or grounding devices.
In dry rooms for the human life, the voltage is more than 42V, in raw and especially wet rooms, boilers, steel and reinforced concrete tanks, wells and on Earth - over 12V.
Esdi fears under tension, the electric current flows through his body.
The current effect depends on many factors: its kind (variable or permanent); with alternating current - from its frequency; Forces (or stresses), current flow duration, the path of passage through the body, physical and mental state of the person.
The most dangerous for a person is an alternating current with a frequency of 50 ... 500Hz. In this case, the ability to independently exempted from contact with parts of the installation that are under voltage, in most people is preserved only with a very weak current (up to 10m).
The strength of the current passing through the human body depends on the voltage of the installation and the resistance of all elements of the electrical circuit.
Leather resistance and internal organs have a flow in the human body. Dry human skin has a resistance about 100kom, wet - about 1kom, and internal organs - 0.5 ... 1kom. However, when calculating the overall body resistance is made to 1k.
It is known that when the current flows, the skin resistance drops, and the cells of the internal organs are reborn, therefore the longer a person is under the influence of the current, the stronger and more seriously the consequences of the defeat.
The deadly electric shock may occur as a result of a heart or breathing stop. With long-term current action (from a few seconds to several minutes), it is possible to simultaneously terminate their operation.
As a result of the impact on the heart of an electric current with a frequency of 50 Hz, a chaotic reduction of the individual fibers of the heart muscle occurs - the so-called fibrillation, in which the heart of the heart is terminated, which leads to a stop of blood flow and the rapid onset of death.
Currently, the amount of current leading to death is taken 100mA with the duration of its flow in the human body more than 2C. On the phenomena of the effects of AC and DC, per person can be judged according to the data given in Table. 8.1.
The most danger of a person is being subjected when the current passes through vital organs (heart, light) or cells of the central nervous system.
When the electric current is turned off exceeding 50mA, the normal operation of the heart itself is not restored. However, the lack of visible signs of life - respiratory movement and heartbeat - does not mean the actual onset of death. First, such phenomena are accompanied by a severe shape of shock, secondly, even with the cessation of breathing and heartbeat, i.e. Upon the occurrence of clinical death, a person can still be saved with artificial respiration and indirect heart massage, if you start spending them immediately.
A healthy person has a period of clinical death up to 7 ... 8min.
It has been established that at the time of electric shock, the physical and mental state of a person is of great importance: if a person is hungry, tired, inxicane or unhealthy, then the electrical resistance of its body decreases and the probability of severe lesion increases. Under the observance of the safety rules, the likelihood of electric shock is small.
Table 8.1.
Manifestations of electric current on the human body
| Current, Ma. | Alternating current | D.C |
| Less than 1. | Not felt | Not felt |
| 1...8 | Feelings are painless. Muscle management is not lost. Perhaps independent exemption from contact with parts under voltage | Easy itch |
| 8...15 | Feelings are painful. Muscle management is not yet lost. Perhaps independent exemption from contact with parts of the installation that are under voltage | Feeling warmth |
| 20...50 | Feelings are very painful. Strong muscle contractions. Breathing is difficult. It is impossible to free yourself from contact with parts of the installation that are under voltage. | Reduced muscles |
| 50...100 | It is possible to fibrillation of the heart, immediately leading to death | Palsy of breathing |
| 100...200 | The occurrence of heart fibrillation, immediately leading to death | - |
