Safety measures for fire resistant cable wiring
【1】 Fire prevention measures for indoor and outdoor wiring
1. Reasonable design
When wiring indoors and outdoors, it is necessary to choose the correct route, try to take shortcuts and straight paths, avoid twists and turns, and reduce cross overs. At the same time, when selecting line conductors, the correct type of conductor should be selected based on the specific environmental characteristics, usually taking into account factors such as moisture resistance, moisture resistance, heat resistance, and corrosion prevention to prevent fire accidents.
2. Strict construction
When installing indoor and outdoor circuits, the burial of fixed components, the connection and laying of wires must be strictly carried out according to regulations to ensure quality and prevent accidents. Especially when wires pass through walls, they must pass through wall sleeves, otherwise they are prone to wear and tear, leading to leakage, short circuit, and fire.
3. The wiring should meet the requirements
In actual production; In daily life, electrical equipment is located in different environments and requires different types of wires and cables to be used. The installation and laying methods should also be suitable to ensure the safe operation of wires in various environments and prevent the occurrence of fires. In order to ensure the safe operation of indoor and outdoor lines, attention should be paid to maintaining a certain distance between lines, between wire fixing points, and between lines, pipelines, and ground during wiring to prevent short circuits from causing fires.
4. The wire connection should be firm
The connection between wires or the connection between wires and electrical equipment is the main area that causes excessive contact resistance and local overheating and fire. Therefore, the wire connection should be firm to prevent loosening, oxidation, etc. of the contact surface. The insulation strength of the insulation material wrapped around the joint should be the same as the original wire.
5. Regular inspection
In order to ensure the normal operation of indoor and outdoor circuits, regular inspections should be carried out. In the inspection of the circuit, it is necessary to correctly and reasonably arrange the usage time of electrical equipment based on whether the circuit can withstand the existing total electricity consumption. Check the connectors of the circuit for looseness and sparking, and reinforce or replace the old and aged wires. At the same time, temporary connected lines should be dismantled in a timely manner to avoid fire accidents.
【2】 Fire prevention measures for cable wiring
1. Standardized construction
When laying cables, construction personnel must ensure construction quality and standardize construction. During construction, it is necessary to prevent mechanical damage caused by excessive traction, excessive bending, incomplete filling, and insufficient burial depth. The intermediate joint and terminal head of a cable are collectively referred to as the cable head. The cable head is a key part that affects the insulation performance of the cable and is most likely to become a source of ignition. Therefore, before putting the cable head into operation, it is necessary to measure its voltage resistance and insulation resistance to ensure construction quality and good connection of the joint.
2. Sealing cable holes
The holes where cables pass through floors, walls, cable trenches, channels, and cable shafts must be tightly sealed with non combustible materials for isolation to prevent the spread and expansion of cable fires; Fire barriers or doors should be installed at the forks of cable trenches and channels, as well as at the entrances of cables to buildings. The pores through which cables pass through the fireproof partition wall should also be sealed with non combustible materials; When cables pass through floors, walls, and other places, if metal pipes are used, the gaps between the metal pipe openings should be tightly filled with asbestos or asbestos mud.
3. Using cable fireproof materials
Common cable fireproof materials include fireproof coatings. Refractory trough box, fire-resistant partition board, fire-resistant blocking material, fire-resistant mesh, etc. The use of fireproof materials can prevent heat transfer, prevent direct damage to flames, narrow the fire range, and prevent the spread of fires, which has a good effect.
4. Strengthen testing and maintenance
It is necessary to regularly inspect and maintain cables, strengthen line inspection, withstand voltage and load measurement, and promptly eliminate faults and temperature rise to ensure the safe operation of cables and prevent accidents during operation.
【3】 Fire protection requirements for temporary power lines
Temporary power lines are mainly used for surprise projects and short-term electricity usage. Due to rough wiring, improper installation, loose pipelines, and excessively small wire sections, temporary electricity can cause overheating or disorderly pulling and connection of wires, resulting in wire collisions or poor contact and causing fires.
Temporary power lines should strengthen fire prevention measures:
Temporary power lines should be approved by relevant departments before installation and laying. And designate specialized personnel to be responsible for safety precautions, and promptly remove them after use. According to the specific environmental characteristics, correctly select the type and cross-section of the wire, and arrange the wiring reasonably. Temporary overhead power lines shall not obstruct personnel passage or threaten personal safety, and wires shall not be hung on trees to prevent wire wear and leakage, which may endanger personal safety. The power supply of temporary power lines should have good safety protection devices. When power is stopped, the power supply to the temporary line should be cut off. When the outdoor temporary line encounters heavy storm, the power supply shall be cut off temporarily and the work shall be stopped.
【4】 Grounding and zero connection
Grounding and neutral connection are important safety measures to prevent electrical circuits from being subjected to lightning overvoltage or accidental electrification of electrical equipment casings, resulting in electric shock hazards.
Grounding refers to making a good electrical connection between a certain part of electrical equipment and the ground through a grounding device. When a certain electrical equipment collides with the casing or insulation breakdown causes the equipment casing to be electrified, the grounding current will simultaneously form a circuit along the protective grounding device.
Because the human body resistance is large, while the grounding resistance of the protective Earthing system is small, the larger fault current flows to the earth through the grounding, and only a small amount of current flows through the human body, thus ensuring personal safety. If there is no grounding device, all fault currents will flow from the human body to the ground, resulting in a personal electric shock accident. Zero connection is the connection between the metal parts of electrical equipment that are not charged during normal operation and the zero line of the power grid. When the insulation of a certain phase of the equipment is damaged to the ground or collides with the shell, that is, it forms a phase zero closed circuit with the zero line. At this time, the short-circuit current is high, which immediately causes the protective device to act, causing the faulty equipment to disconnect from the power supply. To adopt protective grounding, in addition to working grounding, the zero line must also be grounded again at regular intervals. Grounding again is an indispensable safety measure in the protective grounding system. Its function is to reduce the zero line to ground voltage when there is a grounding short circuit or equipment collision in the power system. When the zero line breaks, the degree of fault can be reduced.
【5】 Short circuit protection
When a short circuit occurs in an electrical circuit, the thermal effect, magnetic effect, force effect, and voltage drop of the short-circuit current will have serious consequences for conductors, electrical equipment, energy users, and the entire power system. Therefore, short circuit protection should be provided for electrical circuits to prevent accidents from occurring. In short-circuit protection measures, fuse protection and automatic air switch protection are mainly used.
A fuse is a protective device for short circuits or overloads in power systems and electrical equipment. Generally installed at the power supply end of the protected network or equipment, when an overcurrent fault occurs, the melt melts, isolating the network from the equipment. To cut off the power supply line according to the expected current and predetermined time, it is necessary to choose a melt with appropriate rated current, and it is strictly prohibited to replace it with steel wire. Only in this way can we effectively protect electrical circuits or equipment from short circuits and overloads.
The automatic air switch is used for making and breaking circuits under normal conditions and reconnecting circuits after faults, and has functions of overcurrent protection, overload protection, and undervoltage protection. In order to ensure that the automatic air switch can operate reliably in the event of overload or short circuit in the distribution line and electrical equipment, protecting the wires, cables, and equipment from being burnt out or causing a fire due to overheating. Therefore, it is necessary to choose the appropriate switch type correctly to truly play a protective role.
【6】 Causes of Transformer Fire and Fire Prevention Measures
The main causes of transformer fires are: overload operation of transformers, causing temperature rise, resulting in poor insulation, poor stacking of transformer cores or aging of insulation between chips, resulting in increased iron loss and overheating of transformers; Transformer coils are mechanically damaged or damp, causing interlayer or interturn short circuits and generating high heat; Oil seepage and leakage from transformer oil tanks, bushings, etc., resulting in surface dirt and burning when exposed to open flames; Poor contact at transformer wiring, tap changer, etc., causing local overheating, etc.
The main measures to prevent transformer fires are: before installation, pay attention to checking the insulation of the transformer to ensure good insulation of all parts, and ensure that the rated voltage of the transformer is consistent with the power supply voltage; When installing, pay attention to firm wiring and reliable grounding; Pay attention to the measurement of transformer current and voltage during operation to prevent overload operation; Strengthen the inspection of various components of the transformer in daily life, and promptly handle any abnormal phenomena such as damage or oil leakage; Control the oil temperature below 85 ℃, conduct regular sampling and testing of the oil, and promptly replace and handle any deterioration or acidity exceeding the specified value. While taking fire prevention measures for transformers, corresponding fire prevention measures should also be taken for transformer rooms,
1. The oil immersed power transformer room should adopt a building with a first level fire resistance rating, and the door should be non combustible or difficult to burn.
2. Oil immersed transformers should generally be installed in the transformer room and should have oil storage facilities.
3. The transformer room should have good natural ventilation, and the indoor temperature should not exceed 45 ℃. If the room temperature is too high, mechanical ventilation can be used.
4. A certain distance should be left between the transformer shell and the wall, and it should comply with relevant requirements.
5. The transformer room should not be filled with other items and should be kept clean, with no oil or water on the ground.
【7】 Fire causes and fire prevention measures for distribution boards
The distribution board is the intermediate link between the power supply and distribution of electrical equipment, which can be divided into lighting distribution boards and power distribution boards according to the different devices it controls. The main reasons for a fire in a distribution board are: the wiring of the distribution board is not firmly connected to electrical appliances, instruments, etc., resulting in excessive contact resistance; The selection of switches, fuses, and instruments does not match the actual capacity of the distribution board; Long term overload operation; The fuse selection of the fuse does not comply with regulations; Sparks and arcs are generated when the switch of the distribution board is pulled or fused.
The main measures to prevent fire in distribution boards include: the metal frame of the distribution board, the iron panel surface, and the metal chip shell of the panel equipment should be well grounded, and the grounding resistance should not exceed 4 ohms; The wiring of the distribution board should use insulated wires and prevent misconnection, leakage, and poor contact; When various knife switches and circuit breakers installed on the distribution board are in a power off state, the blades and movable parts should not be electrified; When installing distribution boards in places with combustible dust and fibers, iron sheet sealed distribution boxes should be used; Explosion proof distribution boards should be used in places with explosion hazards; The distribution board should be kept clean, and combustible materials such as clothes, gloves, and wires should not be stacked nearby. While strengthening fire prevention in distribution boards, strict fire prevention measures should be taken for high and low voltage distribution rooms.
1. The high-voltage distribution room should be a building with a first and second level fire resistance rating. The fire resistance rating of the low-voltage distribution room should not be lower than level three. The windows of the distribution room should have measures to prevent rain, snow, water, and small animals from entering. When high and low power distribution devices are in the same room, the distance between them should not be less than 1m.
2. Each oil filled electrical equipment, such as circuit breaker, Voltage transformer, etc., shall be installed in the compartment with partitions on both sides, or in the explosion-proof compartment. When the total oil volume exceeds kilowatt, it shall be installed in a separate explosion-proof compartment. Alternatively, complete sets of high and low voltage distribution devices can be used. If the total oil volume is more than 60 kg, such as oil immersed Voltage transformer, there should be oil storage facilities or oil retaining facilities.
3. The holes left by connecting busbars, cables, ventilation ducts, etc. that pass through walls, floors, and floors should be blocked with refractory materials to prevent the expansion of the fire after the oil filled equipment catches fire.
4. A certain number of fire extinguishing equipment should be equipped in the distribution room.
【8】 Fire Causes and Fire Prevention Measures of Electric Motors
The main reasons for motor fires include improper use or insufficient maintenance, resulting in short circuits or grounding between phases and turns of the motor, as well as phase failure and overload operation; Poor contact at the contact point of the connecting coil and excessive iron loss; The power supply voltage is too high or too low, and the wiring method is incorrect; The power frequency is too low; Bearing wear, rotor scanning and boring, coil turn to turn open welding, short circuit open loop, open circuit operation, etc.
The main measures to prevent motor fires include selecting the correct motor model and capacity according to the usage requirements of the motor. Generally, the motor capacity should be about 10% greater than the power of the machinery carried; Install the motor correctly according to its model and purpose, keeping the motor and starting device at a distance of more than 1m from combustible materials, and installing it on a non combustible base; The power cord used for the motor must be protected by a metal hose or plastic sleeve near the section of the motor. The connection between the other end and the motor inlet box should be well fixed. The motor and power cord should be grounded, and the grounding wire should be firmly fixed on the motor bolt.
Select appropriate protective devices based on the model and capacity of the motor. Strengthen the inspection and maintenance of electric motors, timely clean and maintain cleanliness, and add lubricating oil in a timely manner; Combustible or flammable materials are not allowed to be stacked around the motor, and no items are allowed to be stacked near the starting part to avoid affecting operation. The passage from the motor and connected machinery to the switch should be kept unobstructed. Strictly control the operating temperature of the motor, and the temperature rise during operation should generally not exceed 55 "E. Strictly follow the operating procedures and eliminate any unsafe factors in a timely manner. After the motor is used, the power supply should be cut off in a timely manner.
【9】 Fire hazard and fire prevention measures of lighting equipment
1. Fire hazard of lighting equipment
Lighting equipment is an electrical device that converts electrical energy into light energy. Commonly used include incandescent lamps, fluorescent lamps, halogen tungsten lamps, high-pressure mercury lamps, stage spotlights, etc. Its fire hazard is:
The high temperature and high temperature radiation on the surface of the lamp can easily scorch nearby combustible materials; The bulb is broken, and the hot filament can ignite combustible materials. The power supply voltage exceeds the voltage marked on the bulb, the glass shell of high-power bulbs is unevenly heated, and water droplets splash on the bulb, all of which can cause the bulb to burst. The temperature of the filament is relatively high, and after a certain distance of air cooling, there is still a high temperature and a certain amount of energy, which can cause the combustion of combustible substances; The contact part of the lamp head may generate heat or sparks due to poor contact, as well as short circuits caused by twisting the lamp head when it is loose from the glass shell, which may also cause fire accidents; Ballast overheating can cause combustible materials to catch fire. When the ballast operates normally, it also consumes electricity and has a certain temperature. If the heat dissipation conditions are not good or the matching with the lamp tube is not reasonable, or other accessories fail, the internal temperature will increase and damage the insulation strength of the coil, forming a turn to turn short circuit. This will generate high temperature, which will cause the surrounding combustible materials to be baked and ignited. Combustible dust and fibers can accumulate on the light bulb and ignite.
2. Fire prevention measures for lighting equipment
Different types of lighting fixtures shall be selected according to the fire hazard of the place where the lamps are used and the environment. For example, waterproof lamps shall be selected outdoors, and explosion-proof lamps must be selected in places with explosion hazard, which shall meet the explosion-proof requirements on site. Between incandescent lamps, high-pressure mercury lamps, and combustible materials; The distance between halogen tungsten lamps and combustible materials should not be less than 50cm. The wires used near halogen tungsten lamp tubes should use heat-resistant wires insulated with glass fibers, asbestos, porcelain tubes, etc., instead of directly using insulated wires with flame retardancy to prevent the high temperature of the lamp tube from damaging the insulation layer and causing short circuits. It is strictly prohibited to use paper, cloth, or other combustible materials to cover the lighting fixtures. Combustible materials are not allowed to be stacked directly below the light bulb. The light bulb in the warehouse should be installed above the aisle, and natural lighting should generally be used in the combustible material warehouse. If lighting is necessary, bulbs below 60W can be used, preferably with glass covered lamps. However, halogen tungsten lamps, fluorescent lamps, and lamps above 60W are not allowed. When installing incandescent lamp ballasts, attention should be paid to ventilation and heat dissipation, and ballasts should not be directly fixed in combustible ceilings, counters, or exhibition kitchen windows; The voltage and capacity of the ballast and the lamp must be the same and matched.
【10】 Fire hazards of electric heating equipment