A mine + 620m level 33# mining surface one agreement team is working on the eye, suddenly there is a stop, the shift squad leader will stop the operation, exit the operation point, and inform the class clerk (part-time electrician) to eliminate equipment failure. Since the working face is about 800m away from the + 620m horizontal distribution point (see Figure 1), the electrician saves the problem. When the + 620m horizontal distribution point feed switch is not powered off, the magnetic starter is turned on and the electrification is removed. Failure, accidentally touched the AC 660V charged body, and died of electric shock. After the scene investigation, it was found that:
(1) The leak detection relay in the substation of the mining area is not put into use;
(2) + 620m The horizontal feed distribution point feed switch is in the closed state, and no warning signs are hanged;
(3) The working face magnetic starter drum-shaped explosion-proof casing is opened, and the inner core body is drawn out;
(4) face the magnetic starter, coal drill integrated protection device housing â‘£ no protective earth is mounted;
(5) The working face coal electric drill comprehensive protection device 4 to coal electric drill about 40m rubber cable is not suspended, there are 3 joints in the middle, multiple broken skins to expose the core wire, and the coal electric drill is not connected with explosion-proof bolts.
From this accident case analysis, the following lessons can be drawn:
(1) The operator does not obey the rules and regulations, and the illegal operation is the main cause of the electric shock accident;
(2) When the leakage protection device is not put into use, when the operator touches the electrified body, the feed switch is not tripped and the power supply is cut off, which increases the risk of electric shock to the operator;
(3) The operator is not trained to be employed or has insufficient training and education, and the safety awareness is weak, resulting in illegal operation;
(4) The hidden dangers of insecurity have not been rectified in time. According to statistics, in the past mechanical and electrical accidents in coal mines, electromechanical electric shock accidents accounted for about 8% of total accidents. Therefore, it is urgent to strengthen the safety management of electromechanical equipment and take further preventive measures.
2 The law of the occurrence of electric shock accidents
In the production process of coal mines, the premise of electric shock accidents is that the human body touches the exposed live conductor or touches the electrical equipment casing that is charged due to insulation damage, causing injury to the human body caused by current. According to the way the human body touches the charged body and the leakage device and the way the current passes through the human body, the electric shock accident can be divided into a single-phase electric shock accident, a two-phase electric shock accident or a two-wire electric shock accident, and a stride electric shock accident.
3 types. However, from the analysis of the situation of electric shock accidents, there are often the following rules:
(1) Low-voltage equipment has a high electric shock accident rate. Safety in coal mines
In the production process, most of the electromechanical equipment and power supply equipment used underground are low-voltage equipment, which has a wide distribution, many opportunities for contact with operators, and long time. Operators often have poor management and are paralyzed, and at the same time lack certain safe electricity. Knowledge, the rate of electric shock accidents is high.
(2) The rate of electric shock accidents between mobile devices and handheld devices is high. In the underground production and operation, these devices are large in quantity, mobile, and not used by people. Therefore, it is inconvenient to manage and has many safety hazards. At the same time, these devices are tightly held in the hands of the operators when used, and it is often difficult to leak electricity. get rid of.
(3) The rate of electric shock accidents due to illegal operation or misoperation is high. Mainly because the workers are not trained or have insufficient training and education, the awareness of safe operation is weak, misuse or illegal operation, or the use of safety precautions, lack of electrical equipment, and the risk of survival, Caused an accident.
(4) The seasonality of electric shock accidents is obvious. In the second and third quarters of each year, there are many electric shock accidents in the coal mines, which are also the most concentrated. The main reason is that there are many rains in this season, the workplace is wet, the insulation performance of electromechanical equipment is reduced, and the human body is sweaty and the skin resistance is reduced.
(5) The non-standard power transmission line and the use of electrical equipment that does not meet the safety requirements have high electric shock rate. Most small coal mines do not use mining cables and use black leather wires, gel lines, sheath wires, etc. for power transmission, or do not use mining explosion-proof switches, explosion-proof lights, etc. Replacement of switches, general lighting heads, etc., cable suspension failure or non-suspension, serious insulation damage, line chaos, random connection and ubiquitous bare joints, plus small coal mines to reduce input, small road section, narrow space, The water in the wells is wet, and these unsafe facilities can easily cause electric shock during production, operation or maintenance.
3. The main cause of electric shock accidents
It is not accidental that there are electrical and mechanical equipment or power supply lines in coal mines. There are many main and objective reasons. However, based on the analysis of some statistical data and the whole process of electric shock accidents, the main causes of electric shock accidents can be summarized as follows:
(1) Lack of safety knowledge in the use of electromechanical equipment. If you touch the charged body or the leakage device directly by hand; operate the high-voltage switch or equipment with live power; pull the line or install the device with electricity; if someone touches the power, the electric shock is not taken first and the electric shock is directly pulled.
(2) Violation of the safe operation procedures and illegal operation of electromechanical equipment. If the equipment casing is not grounded; electrify to repair or relocate electrical equipment; do not use insulation (use) or use uninsulated or insufficiently insulated work (use); when the line or equipment is overhauled, the personnel are not evacuated from the site. There is no warning or un-hanging signboard in the place where the power is charged, so that the personnel may mistakenly enter the live place, accidentally touch the live line or equipment, and send power by mistake.
(3) Improper installation and maintenance of electrical equipment or power supply lines. If the cable is messy, messed up or the wiring is not standardized, the distance or height of the suspension or suspension is not enough, or even placed on the ground; the equipment has no support, and the water is damp; the missing or damaged parts of the equipment are not replenished or replaced in time, and the matter is perfunctory. Make the device sick and run.
(4) The equipment quality is poor and the safety protection performance is unqualified. If the insulation performance of the equipment is poor or unqualified; the cable insulation is seriously damaged; the equipment lacks sufficient safety protection devices; the safety spacing, safety passages and inspection intervals of the equipment are insufficient.
(5) Accidental factors. It is mainly caused by electric shock accidents that occur under unexpected circumstances.
From the above various reasons, we can draw the conclusion that:
In coal mine safety production, most of the electric shock accidents are not composed of a single factor, often caused by two or more factors. The law of electric shock accidents is not static, and often due to various factors and the promotion of new technologies. A change has occurred. Therefore, in the coal mine production process, the occurrence law of coal mine electric shock accidents should be continuously analyzed and summarized, and preventive and safety protection measures should be found to reduce the incidence of mechanical and electrical accidents, and provide a reliable scientific basis for coal mine safety production and reduction of electric shock accidents.
4. Measures to prevent electric shock accidents
In order to prevent electric shock accidents in coal mine production and reduce accident rate, on the one hand, we must strengthen the technical management of equipment and the organization and management of operators. On the other hand, we must do a good job in the implementation of preventive measures, preventive measures, and effectively prevent the occurrence of electric shock accidents. The main measures are as follows:
(1) Strengthen the training of the professional and knowledge of the supply and use of electrical and mechanical and electrical equipment, safe use of electricity, and independent security. Training work can not be in the form, we must pay attention to actual results, and combine theory with practice to effectively improve the overall operation level of operators. It fundamentally reduces or eliminates electric shock accidents caused by the lack of necessary electrical safety use and operational knowledge of operators.
(2) Prevent personal contact or proximity to live conductors, strengthen isolation and screen protection of live equipment, and hang signboards to warn workers to maintain a certain safe distance from live parts and control unsafe factors.
(3) The neutral point of the transformer underground and the power supply to the underground shall not be directly grounded. Its main purpose is to prevent electric shock accidents and reduce the risk of electric shock. The transformers that most small coal mines supply to the underground are still connected by neutral grounding. According to calculations, in the power supply system where the neutral point of the transformer is directly grounded, when the person stands on the ground and touches one phase of the live conductor, the electric shock current through the human body is 2.47 times that of the power supply system whose transformer neutral point is not grounded, which is invisible. The danger of an electric shock accident.
(4) Underground Network must be installed to run reliable leakage protection device and effectively put into use, the metal casing of electrical equipment must meet the requirements of the protective earth. These two protections are effective measures to fundamentally reduce the risk of human electric shock in the event of an electric shock accident. They cannot reduce their integrity requirements, and they cannot be ineffective.
(5) Improve the insulation performance of electromechanical equipment. It is strictly forbidden to use non-coal-specific, poorly insulated agricultural machinery or electromechanical equipment in coal mines. Good insulation is an important measure to ensure the normal and safe operation of equipment and power supply lines and to effectively prevent electric shock accidents.
(6) Electrical equipment that is frequently in contact with people should be powered by low voltage of 127V and below as required to reduce the risk of electric shock. Such as handheld electric drills, lighting equipment, lifting signal devices and control circuits, buttons and so on.
(7) Strictly implement the power supply and consumption approval system, and at the same time strengthen the inspection and supervision of electrical equipment, find problems and stop maintenance in time, ensure that the equipment is running without disease, eliminate the accident in the bud, and control the accident to prevent it from happening.
5 Conclusion
The electric shock accident occurred in the coal mine production process, although there are objective reasons (unpredictable natural disasters) and subjective reasons (operators do not obey the rules and regulations, illegal operation or improper installation, maintenance, etc.), but if the equipment The operation law is analyzed in detail, and the unsafe hidden dangers are seriously and timely rectified, and preventive measures are taken in a targeted manner to prevent the occurrence of coal mine electromechanical electric shock accidents.
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