Causes and preventive measures for underground electrical accidents
Due to the harsh natural environment and geological conditions, the underground electrical equipment is frequently started, the load changes greatly, the voltage fluctuation is large, the equipment is burnt due to overload, short circuit, electric leakage, electric arc, electric spark failure, mine fire, gas coal dust explosion, electric shock casualties may occur at any time. In addition, distribution lines, switches, fuses, latch holders, electric heating equipment, lighting fixtures, motors, etc. may cause electrical damage, become a source of ignition, or cause electric shock.
Second, the harm of electric shock and prevention measures
1. Harm of electric shock
The human body touches the live conductor or the equipment casing or cable or wire that is charged due to insulation damage. Due to the special working environment conditions in the underground, the possibility of electric shock is greater. The destructive effect of electric shock on human tissue is very complicated. Generally, the damage to the human body can be roughly divided into two cases: electric shock and electric shock. Electric shock refers to the current passing through the human body during an electric shock, which damages and destroys the respiratory organs, heart and nervous system under thermochemical and electrolysis. In most cases, electric shock can kill people, so it is the most dangerous. Electrical injury refers to the destruction of external organs, such as burns, due to current passing through a part of the human body or arcing the human body. When the burn area is not large, there is no danger to life. Usually, the human body is exposed to electric shock and electric shock at the same time.
The danger of electric shock to the human body is determined by many factors, but the amount of current flowing through the human body is the main factor determining the role. The maximum current that the human body can get rid of is 16 mA (called the current). Usually, the human body's electric shock current is below 15 to 20 mA, and when the DC is below 50 mA, there is no danger to life. But when the human body's electric current is longer than the current, and there is no rescue, life is dangerous. When the human body's electric shock current reaches 100 mA (approximately equivalent to the current flowing when the 25W bulb is connected to 220 volts), life is absolutely dangerous.
The amount of current flowing through the body is related to the body's resistance. The greater the body resistance, the smaller the current through the body, and vice versa. The human body resistance is a large variation. When the human body has a wound and sweats, its value is greatly reduced compared with normal, and it decreases with the lengthening of the electric shock. Therefore, the electric shock in this case is more dangerous. .
The electric shock current flowing through the human body is related to the voltage applied to the human body. The larger the electric shock voltage, the larger the electric shock current and the more dangerous it is.
The longer the electric shock current flows through the human body, the greater the degree of damage to the human being caused by electric shock. Therefore, even if it is a safe current, if it flows through the human body for a long time, it will cause casualties. China's regulation of 30 mA current, flowing through the human body for 1 second is safe. Therefore, when the human body is in shock, how to get the electric shock off the power in the shortest time is very important for the rescue of the life of the electric shock.
2. Prevention measures for electric shock
(1) Electrical equipment (including cables and wires) shall not be repaired or removed under power. Before the maintenance or relocation, the power supply must be cut off and tested with an electroscope that is compatible with the power supply voltage. All switch handles should be locked when the power is turned off, and the warning sign "Nobody is working, no power is allowed" is hoisted. Only the person performing this work has the right to remove the card. Strictly enforce "who has a power outage and who sends power." The system is strictly forbidden.
(2) To operate underground electrical equipment, the following provisions must be observed:
1 Non-professional or on-duty electrical personnel shall not operate electrical equipment without authorization.
2 When operating the main circuit of high-voltage electrical equipment, the operator must wear insulated gloves and electrical insulation boots or stand on the insulation platform.
The operating handle of the 3127 volt handheld electrical equipment and the parts that must be in contact during operation should have good insulation.
4 Ordinary portable electrical measuring instruments are only allowed to be used at locations below 1% of gas concentration. Underground explosion-proof electrical equipment must be inspected and qualified before entering the well.
5 It is strictly forbidden to “privately connect†the power supply line.
6 underground power supply insists on the use of leak detection protection device and electric coal drill comprehensive protection device.
(3) Prevent personal electric shock or proximity to live conductors.
1 Install the exposed live parts of electrical equipment at a certain height, or fence.
2 The conductive parts and cable joints of various electrical equipment in the underground must be enclosed in a sturdy outer casing, and a mechanical locking device is arranged between the operating handle and the cover.
3 The entrance or door of each transformer (with) is hoisted with the "non-worker, no entry" warning sign; the unattended change (match) electric station must be closed and locked; when there is high-voltage electrical equipment in the underground squat room, A “high-pressure danger†warning sign should be placed at the entrance and inside the room.
(4) For electrical equipment that people often come into contact with, voltages with low voltage levels are used. The rated voltage of devices such as downhole lighting, handheld electrical equipment, telephones, and signals should not exceed 127 volts.
(5) Precautions for preventing electric shock in underground coal mines
Non-professional electrical personnel shall not arbitrarily manipulate, overhaul or operate electrical equipment.
2 Do not stop and send electricity by yourself.
3 Beware of injury to the overhead line. Longer tool carrying metallic utensils, metal pipe running under the overhead wire, which is forbidden on his shoulders.
4 walking down the mountain, it is strictly forbidden to hold the cable. Otherwise, once the cable is leaked, the consequences are serious.
5 It is strictly forbidden to sit on electrical equipment and cables, and do not touch electrical equipment and cables at will.
Third, the harm and prevention of leakage
Leakage will pose a great threat to the human body, equipment and even mines: when the human body touches the leakage equipment or cable, it will cause electric shock and casualties; the electric detonator can be detonated in advance; if the electrical equipment leaks, the power supply will be expanded into a short-circuit fault and burn the equipment. Fire.
Precautions:
1. Avoid immersing cables and electrical equipment in water to prevent mechanical damage such as crushing, collision, excessive bending, scratching, and stab wound.
2, the wire connection should be firm, no burrs, anti-loose.
3. When repairing electrical equipment, it is necessary to operate according to the regulations. It is strictly forbidden to leave conductors such as tools and materials in electrical equipment.
4. Do not add extra parts to the electrical equipment at will. If it is necessary to set up, it must comply with the relevant regulations.
5. Set the protective grounding device.
6. Compensate for the capacitor's capacitance to ground.
7. Set the leakage protection device.
8. Avoid long-term overload or over-running of electrical equipment and cables, causing leakage due to insulation aging.
9. Conduct electrical performance measurement of electrical equipment and cables on a regular basis.
10, equipment maintenance, should avoid stop, power transmission operation errors, live work or work accidents caused by personal contact and leakage.
Fourth, basic knowledge of electric shock first aid
In the event of an electric shock accident, rescue should be carried out in accordance with the principle of “two fast, one persistence, one cautionâ€.
1, "two fast" refers to: quickly cut off the power supply, and quickly rescue.
1 Quickly cut off the power supply, so that the electric shocker can quickly get out of the power supply. When there is a power switch or plug near the accident location, immediately turn off the switch or unplug the power supply and cut off the power. When the power switch or plug is too far away from the accident location, if the power supply voltage is lower than 380 volts, the charged body such as the cable can be removed by using dry wooden sticks, bamboo poles, etc., or insulated wire cutters or dry wooden handles can be used. The axe cuts off the power, but you must pay attention to the power supply direction and cut off the power where there is a support. Do not directly pull the electric shocker without the insulation measures to avoid expanding the accident. When the power supply voltage is higher than 380 volts, the protective equipment of the corresponding insulation grade should be worn to cut off the power supply with the corresponding level of insulation equipment. If there is no insulation appliance application communication tool at the accident site, the relevant power supply department should be cut off the accident line.
When cutting off the power or disconnecting the electric shock from the power supply, be careful not to accidentally injure others. In particular, after the electric shock is disconnected from the power supply, the muscles are no longer stimulated by the current, and will immediately relax and fall, causing trauma, which is more dangerous at high altitude, so it should be taken. Corresponding security measures.
When the electric shock is electric shock for the stride voltage ("floor charging" such as a phase fire line is placed on the ground, causing the fire line to be charged within 20 meters, and the closer to the fire line, the higher the potential, but generally the voltage 8 meters away from the fire line The difference will not cause casualties. The rescuer should take care to prevent the electric shock from hitting the voltage. When the electric shocker can leave the power supply by himself, he should jump out of the accident site with one foot or both feet, and must not step out of the accident.
2 Quickly rescue. According to statistics, about 95% of the people who were rescued in the event of electric shock were rescued quickly within 3 minutes after the power was turned off. Therefore, it is also a key link to immediately rescue the power after the power is turned off. First of all, quickly remove the contactor from the power supply to a ventilated and dry place, make it supine, untie its clothes and buckles, and keep warm when the temperature is low. Secondly, according to different diagnostic results, take corresponding emergency measures: for those who are “consciousâ€, they should pay attention to rest observation. If it is considered that the time of electric shock is longer, it is necessary to send it to the hospital for examination, and clearly inform the doctor that the patient is electrocuted; Persons with electric shock who stop breathing should use the "mouth-to-mouth artificial respiration method" for rescue; those who have "breathing and heartbeat stop" should be rescued by "thoracic external cardiotomy"; for "breathing and heartbeat" Those who stop the electric shock should be rescued by the "mouth-to-mouth artificial respiration method" and the "thoracic external heart compression method". The electric shock to the latter three cases should be actively rescued on the one hand, and on the other hand, the hospital should be called for help.
2, "one insistence": that is, insist on artificial respiration. Rescuers must have patience in the artificial respiratory rescue of electric shockers, even if there is a glimmer of hope, and can not stop on the way to the hospital. For electric shock absorbers, artificial respiration is the most effective rescue method. Some electric shockers need to be rescued for hours or even tens of hours before they can wake up. The record of the rescue recorded in our country is three and a half hours after artificial respiration. The electric shocker saved.
3, "a prudent": that is, the use of excitatory drugs. If you use adrenaline carefully, if you use it at will, you may accelerate the death of the electric shock. Only after the hospital has been diagnosed by the instrument can you decide whether to use it. In addition, you must not pour water on electric shockers or use other incorrect methods such as "buried with sand, pressure" and other "hearsays" to rescue.
V. Accident case
1. The "6•24" electric shock accident occurred in Liancheng County XX mine, causing Li Xlan and Li Xfei to die in the coal mining operation. The direct cause of the accident was that the electrician was repairing and installing the electric coal drill integrated protector. At this time, this is easy to save, reduce the amount of maintenance work, opportunistically serious violation of the "coal safety regulations" does not ground the electric drill shell, artificially the electric leakage protection action mechanism of the electric coal drill integrated protector with the wooden pin wedge, resulting in The earth leakage protection device does not work. Since the electric coal drill was charged due to insulation damage during use, the integrated protector could not cut off the power supply, causing Li Xlan and Li Xfei to die of electric shock during the eye-catching operation.
2. An electric shock accident occurred in the 416 inclined shaft of XXXX Coal Mine in Hucun Town, Ninghua County, and one person died. On October 10, 1996, the miners Zhang × × (undocumented electrician), Fu × ×, Huang × × and other three people, because the pump does not go up the water, go down the well to see the water pump, Zhang × × in the inclined well pump control switch, Pay ××ã€é»„×× to raise the water pump at the bottom of the well to clean up the debris, and lift the pump to a place where the water is slightly shallow. Then the two return to the flat of the bottom of the well, and then pay XX to go. On the slope of the water, Huang×× is still standing in the bottom of the well. Paying ×× called Huang×× left the lane and went to the slope. Huang×× said: “Not afraid, nothing.†Then, Huang×× called the power pump at the upper pump control switch. Zhang Yihe switch, yellow is called "have electricity, electricity", and even fell to the place where the XX station was paid. Zhang × × heard the sound immediately cut off the power. It takes about 30 seconds from power transmission to power off. Huang × × died of electric shock.
The cause of the accident was that the submersible pump was not in good condition and the electric leakage occurred. The mine used neutral grounding voltage transformation and directly supplied power to the underground, without leakage and grounding protection devices.
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