【 Weak current College 】 electrical lines of fire and prevention---Power By 【 China power house network 】

Line due to the erection of an incorrect or installation and use is in violation of safety rules, at any time are likely to form a short circuit, overload or wire local contact resistance is too large, so as to produce a spark or high temperature, resulting in the line of fire. The first section of the electrical circuit of the fire cause and prevention measures
Electric circuit in case of fire, mainly due to the line of a short circuit, overload or contact resistance is too large, producing an electric spark, electric arc or cause overheating for wire and cables, resulting in a fire.
A, short-circuit
(A) definition: electrical wiring in the conductor due to various causes, the line and the line, the line with the zero line (ground) connection, in the loop current moment caused by the sudden increase in the phenomenon known as short-circuiting.
According to Ohm's law, short-circuit resistance suddenly decrease the current will suddenly increased. Hence, circuit, in a very short period of time will issue a lot of heat, the heat not only enables the insulating layer burning, and enables the metal melting, the neighbouring flammable, combustible combustion, resulting in a fire.
(Ii) in the form of a short circuit
The line touches the short circuit between the call; the line between phases and neutral wire (ground) touch call direct grounding; the line touches with the grounding conductor is called indirect grounding.
(3) electrical circuits short circuit of the main reasons are:
1. the use of insulated wire and cable, not according to the specific environment of choice, so that insulation from heat, corrosion, moisture or, loss of insulation capacity.
2. line a lamentable, insulating layer obsolescence or damaged, make a bare wire core.
3. the power supply voltage, the electric wire insulation breakdown.
4. the officers of the installation, repair, or wrong line for live working-time caused a short circuit for touch line.
5. bare wires install is too low, metal accidentally touch the wire; line with metallic objects or small animals fall, crossover between the wires.
6. overhead line wire spacing is too small, span, wire and relaxation, there is a possibility that a two-wire brushing; overhead wire and buildings, trees, too close to the wires and buildings or trees.
7. wire mechanical strength is not enough, lead wire break off contact with the Earth, or broken down in a separate wire.
8. not complying with the provisions to require private la confusion, mismanagement, short circuit caused by improper maintenance.
9. high-voltage overhead lines insulators voltage level is too low, causing the line to short-circuit.
(Iv) measures to prevent short circuits
1. in accordance with the environmental characteristics of the installation wires, consideration should be given to the damp, chemical corrosion, high-temperature locations and rated voltage requirements.
2. wire and wire, wall, roof, metal structures, as well as fixed wire of insulators, vases, there should be a certain distance.
3. from the ground and across the floor and 2m walls of conductors, should have protection insulation of measures to prevent injury.
4. the insulated conductors do not use wire strapping and nails by hanging.
5. insulation resistance on a regular basis.
6. install the line should be the holder of the electrical installation.
7. install the appropriate insurance, or automatically switch.
Second, overload (overload)
(A) definition: electrical lines allow continuous pass without making wire overheated electrical discharge, known as the safe carrying capacity or safety of current. As the current flows through the wire over security current values, called wire overload. Wire overload, generally do not consider the voltage drop in temperature as the standard.
General line, the maximum allowable working temperature of 65 degrees. When the overload, the conductor temperature exceeds this value, the temperature will make insulated accelerated aging and even damage caused by fire, short-circuit.
(Ii) overload of the key reasons:
1. conductor cross-sectional area select improperly, the actual load exceeds the current carrying capacity of the safety wire.
2. in the line access too much or the power of the electrical equipment, exceeding the capacity of load distribution line.
(C) measures to prevent overload
1. the reasonable choice of wire section.
2. avoid chaos pull the wire and excessive access load.
3. regularly check the line and decrease the load and equipment.
4. install the appropriate insurance or auto switch.
Third, the contact resistance is too large
(A) definition: conductor connection is formed on the surface resistance is called the contact resistance. Joint processing of good, the contact resistance; the connection is not strong or other reasons, the connection is bad, it can cause excessive local contact resistance, high temperature, the melting metal discoloration even caused insulating material fuel combustion.
(Ii) contact resistance of the main reasons are:
1. installation of poor quality, resulting in wire and cable, wire and electrical equipment connection point connection is not strong.
2. wire connections stained with impurities, such as oxidation layer, dirt, oil, etc.
3. connection points as the long-term vibration or heat change, so that the connector is loose.
4. copper aluminum mixed received due to improper handling of joints in electric corrosion of contact resistance will increase quickly.
We all know that line powered, electric current through a wire, connectors and equipment would generate heat, this is normal. Connector does well, the contact resistance is small, the connection point of the calorific value is small, you can maintain a normal temperature. If the header isn't good, contact resistance will increase, while the amount of heat generated. Some current, resistance, the larger the calorific value. Therefore, there is a larger contact resistance line segments will strongly fever, a rapid rise in the temperature of the conductor insulating layer of fire caused by, resulting in the vicinity of dust on the wire, fiber, and other substances like, if not handled properly it will cause a fire. Such as cotton mill of motor vibration, it is possible to make joints loose, contact resistance is too large, because local temperature ignition cotton dust or I fire.
(Iii) prevent the contact resistance of measures:
1. should minimize unnecessary connector, the connector for the essential and must be closely integrated with the solid and reliable.
2. copper wire used when splicing, should, as far as possible, then solder processing, should generally be used welding and crimping.
3. copper aluminum should touch the heating system is copper and aluminum connectors and crimp connection method.
4. always check testFound problems in a timely manner.
In order to prevent or reduce the distribution line accident, must be in accordance with the electrical safety code for design, installation, use, strictly in accordance with the positions of responsibility and safety practices, strengthen maintenance management, timely elimination of vulnerabilities, security electrical safety.
The second section of the special places of fire safety requirements for electrical circuits
I. Special damp housing
Special damp housing refers to the bathroom, kitchen, laundry room, and gives off steam.
Insulated conductors moisture causes the insulation performance, or even damage, short circuit. The main reason for this is: (1) wire specifications, model selection misconduct; (2) wire laying unreasonable.
The laying of electrical line should meet the following requirements:
(A) line laying should try to use insulated conductors wearing PVC hard plastic or steel pipes for fire for laying. Steel pipe must be anti-rust treatment, the spout shall take the appropriate waterproofing treatment. You can also open wire with vases. You can also use a protective layer of insulated wires, such as lead leather cord, plastic-sheathed cord out.
(2) considerations for conductors compressive strength, must conform to the line voltage requirements, while wearing pipe should not be lower than 500 volts.
(3) check maintenance electrical circuit must generally take a power check, testing insulation resistance, clear wire surface dust accumulation. Particularly bad previous rainy season, the work must be clean.
2. high-temperature housing
High-temperature heat treatment workshop housing refers, Chamber, burn-in room etc. Due to the surrounding environment temperature is high, so that the wire's secure current dramatically lower, easy lead wire overload. At the same time, the heat is distributed wire, insulated easily burn damage. Therefore, in high-temperature housing wiring, you should also consider the temperature of the surrounding environment, meet the following requirements:
(A) line laying in accordance with security current conductor cross section later determined to be under the actual annual maximum ambient temperature for correction. As far as possible from the heater installation and oven. Connection heater wire, the use of copper conductor glass braided rubber cable and wire for asbestos or hard plastic pipe PVC fire protection.
(2) considerations for laying in the high temperature housing wire easy to aging, it must periodically check test conductor insulation strength.
Third, more dust housing
More dust housing generally refers to the textile mills, cement factories, flour mills and pencil factory, and so have a lot of dust in the workshop. A conductive powders, the greater the risk. Metal powder suspended in space, easy to accumulate on the surface of the wire, wire insulation damage, the live wire core exposed, current will pass these powder leak, causing a short circuit to ground or short circuit, causing combustion phases.
(A) line laying should use wires wear hose downlead or concealed. Wire and tube port, irrigation, asphalt closed electrical equipment should take dust control measures, the lamp cartridge, hanging box, lamp CAP and the motor terminal box should be sealed and often clear the dust of the House.
(2) considerations of fire and explosion hazardous dust environment electrical explosion-proof electrical equipment should be installed.
4. corrosive gas.
Corrosive gas, is the acidic, alkaline, corrosive gases, such as electrolysis Studios, electroplating, etc. Acid-base classes are good, conductive media conductors to corrosion, causing accidents.
(A) line laying application hard plastic pipe PVC fire wear insulated wires laying out, dark, mixed with pipeline attachment shall be for the plastic material. Using pipe laying, should be treated with preservatives. If the current is large, the use of copper, aluminum wire downlead, vases, and coated anti-corrosion paint protection.
(2) considerations for corrosive gases can use electrical equipment contact surface oxidation, contact resistance, contacts overheat, serious, can ignite nearby flammable material. Therefore, you must often eliminate contact surface oxides, bath on the electrode contacts should always deal with clean, ensure a good contact.
5. meeting place
Meeting place is the cinema, theater, Stadium, cultural Palace, clubs, etc., these places are equipped with a stage, stage fuel many, such as scenery, props, curtains, electric lines short circuit, overload can ignite the fuel. In the event of fire, the personnel number, order, evacuation difficult, often result in serious accidents.
(A) cinema
1. line laying should adopt PVC fire hard plastic or steel wear insulated wires laying out, dark.
Arena generally must use copper conductor insulated wire, used for sky-lights, effects, such as moving lights the lamp of the leader should adopt tough rubber sheathed cable (wire) or plastic-sheathed cable.
2. wiring methods should be under load conditions, branch circuit wiring, prevent the same slip road access too much load.
3. considerations
(1) the stage all electrical equipment should be controlled in the background, its total capacity should be line safety matches the current carrying capacity, and set the fuse protection. All exposed live parts must have protective equipment, the socket should also have appropriate cover and cover
(2) sky lights and curtains, not less than the distance between the front surface of 50cm light should also be unprotected network.
(3), forbidden without authorization to increase the capacity, chaos, confusion.
(Ii) open-air Stadium
1. line laying should adopt rubber or plastic insulated copper wires laying, the section should not be less than the requirements of laying 4mm2, and overhead lines are the same.
2. considerations
(1) hanging lamps of the rope should have adequate institutional strength, intermediate wire rope shall be properly equipped with retaining line vases.
(2) the clearance lamps should not be lower than 6m and install shield.
6. flammable building
Inflammable building refers to the Reed, linoleum, bamboo, wood, and other combustible materials of construction of buildings, these buildings apt, damp, causing damage to the insulation of electric circuit, short circuit, or even produce a spark, and cause a fire. Therefore, not appropriate for flammable building in General, such as installing electrical circuit must be installed because of a need, you should take the following fire safety measures:
(A) line laying in inflammable building should not take plastic or rubberCable directly downlead, should not close to the ceiling. Instead, you must use bottles open wire laying and roof truss of the bottom chord cabling, line spacing should not be less than 60mm. Wire cross section should be strictly according to actual load calculation, lighting, switch, electrical installation should comply with the relevant requirements of the installation procedure.
(2) considerations for the conductors through the flammable materials, must wear a protective steel or ceramic pipe, and a line per tube. Control switches, fuse, etc should be installed on a dedicated distribution box.
7. temporary electricity line
Temporary electricity lines, because of the time, people are often not enough to pay attention to, the laying of the humble, components, materials selection is not conditional, making the possibility of a fire.
Temporary power supply line shall be approved by the relevant authorities before installation. Installation should be qualified equipment. Specifies the specialist is responsible for management, in use should periodically check the scheduled removal.
(A) temporary line laying low voltage overhead lines can use bare wires and insulated conductors, but cable shall be not less than the distance between 300mm, span 30m, lines should not be more than the total length should not exceed 500m. Conductor vases, should not be wire hanging on trees, avoid mixing line, such as break. To the electrical equipment of branch lines, must be insulated conductors shall not have the connector in the middle; in branch lines should be installed on the end of the rod crossarm, vases, should not be confused with fixed wire pull out bound.
Temporary power line power supply and operation of local switches and socket should be installed and applied waterproof box protection.
Building of a temporary electricity lines should not be erected along the fuel. Capacity is low, you can use rubber sheath cable or plastic-sheathed soft cable, length must not exceed 100m, plugs and Sockets.
Maintenance equipment, electrical machinery equipment of the shell should have good protective earthing device.
Temporary power supply line, strictly prohibits the use of the "one line" system installation electrical lighting and other electrical devices.
(2) considerations
Jump to a power outage. During the night or work do not need electricity, the power should be cut off temporary line. Outdoor temporary electricity is in use in the event of strong winds, heavy rain, etc., as appropriate electricians should temporarily cut off the power. After the rain, you should also check the lines repeat again to confirm that everything is correct before you power on.