1. Fire hazard of electrical lighting
When the lighting or decorative lamps are working, the surface temperature of the glass bulbs, tubes and the like is high. If the lamp is improperly selected, the occurrence of electric spark, arc or local high temperature may cause the combustibles in the vicinity of the lamp to ignite and burn, resulting in a fire.
Since lighting fixtures are generally installed in places where personnel are produced and inhabited, decorative lighting fixtures are generally installed in crowded places. In addition to causing huge property damage, fires can cause heavy casualties.
1.1 incandescent lamp becomes the source of ignition
When an incandescent lamp is working, its surface will be hot, and the greater the power, the longer the continuous use time, the higher the temperature. Where the surface is in contact with or close to the combustible material, the accumulated heat can ignite the combustible material; in addition, the incandescent lamp has poor shock resistance, is easily broken and exposes the high temperature filament, and the high temperature bulb fragments are also prone to fire.
1.2 fluorescent lamps become the source of ignition
The fire hazard of fluorescent lamps is mainly on the ballast. If the quality of the ballast is unqualified, the heat dissipation conditions are not good, or the rated power is not matched with the lamp, the internal temperature will rise sharply. The long-term high temperature will damage the insulation of the coil, and the short-circuit between the turns will generate a huge amount of heat, and the surrounding will be ignited. Combustible.
1.3 high pressure mercury lamp and sodium lamp become the source of ignition
Excessive temperature rise is the main fire hazard of these two types of lamps. High-pressure mercury lamps and sodium lamps have higher power, generally several hundred watts or more. When lighting, the surface temperature of lamps is very high. In addition, the ballast of the high-pressure mercury lamp and the electronic trigger of the high-pressure sodium lamp have fire hazards.
The fire hazard of the ballast is like the ballast of the above fluorescent lamp, and the electronic trigger may cause heat due to internal capacitor leakage and the like to cause combustion.
1.4 tungsten halogen lamp becomes the ignition source
When the tungsten halogen lamp is in normal working condition, the temperature of the quartz glass tube wall is as high as 500 ~ 800 °C, which can not only burn the attached combustible materials in a short time, but also burn the combustible materials within a certain distance, which is more dangerous than fire. Other general lighting appliances are larger.
1.5 special effects ballroom lights become the source of ignition
Special effects dance hall lights mainly include peak nest lights, scanning lights, sun lights, cosmic lights, skeet lights and snowball lights that do not emit light. It is characterized by the fact that the luminaires are decorated and rendered with an electric motor that often drives the rotation of the luminaire. When the rotation resistance increases or the transmission mechanism is stuck, the motor will heat up quickly, and the props scenes of the stage and other places are mostly combustible materials, and it is easy to catch fire under the high temperature of the motor.
1.6 neon lights become the source of ignition
The neon trigger voltage is above 10,000 volts and requires a special transformer boost. If dust is accumulated on the insulated terminals output from the high-voltage output of the transformer, electric leakage may occur in wet weather, causing fire. At the same time, the long-term power-on will also cause an accident due to the temperature rise and the asphalt on the melting transformer.
1.7 Lighting switch and other facilities become the source of ignition
In the electrical lighting and decoration process, in addition to various lighting and decorative lighting, a large number of switches, protectors, wires, hanging boxes, lamp holders, light boxes, brackets and other accessories are required. These facilities may cause fire damage, such as insulation damage, short-circuit fire, etc. due to improper capacity selection and long-term overload operation.
2. Fire prevention measures for electrical lighting
2.1 Reasonable selection of lamp types
In the case of explosive mixtures or where explosive media is produced, integral explosion-proof devices should be used. For corrosive gases and particularly humid places, sealed or moisture-proof luminaires shall be used, and the components shall be treated with anti-corrosion treatment. In hot and dusty places (such as steelmaking, iron making, steel rolling, etc.), floodlights can be used. Outdoor lighting can be enclosed lamps or open lamps with fire lamp holders.
2.2 Correct installation of lighting, decorative lighting
2.2.1 Installation location
The distance between the lamps and the combustibles shall not be less than 50cm (the tungsten halogen lamps shall be greater than 50cm), and the height of the ground shall not be less than 2m. When the height is lower than this, protective equipment shall be installed, and combustible materials shall not be piled under the bulbs.
2.2.2 Protective cover for lamps
The protective cover of the luminaire must be in good condition. It is strictly forbidden to cover the luminaire with paper, cloth or other combustible materials.
2.2.3 Heat dissipation and insulation of lamps
The power of all concealed and surface mounted lamps on the flammable ceiling should not be too large, and should be dominated by incandescent or fluorescent lamps; concealed lamps and their heating accessories should have good heat dissipation conditions around them. The conductors of the stage concealed lanterns, dance floor lamps and flammable ceiling lamps shall be laid with steel pipes or flame-retardant hard plastic casings; the wires near the tungsten halogen lamps shall be made of heat-resistant insulating sheaths; There should be a rubber ring protection through the keel.
2.2.4 Selection of low temperature ballasts
The use of reliable low-temperature ballasts is not allowed to directly fix the ballasts with elevated temperature on objects such as combustible ceilings. The capacitance and capacity must be the same as those of the lamps.
2.2.5 Installation of explosion hazardous locations
Class 0, Class 10 explosion hazardous areas (0-level area refers to explosive gas, and level 10 area refers to explosive dust area). When an open type lamp is used to make an in-wall type alcove, the access door should be opened to the outside of the wall. And ensure good ventilation. The side to the indoor lighting should be double-glazed tightly sealed, the horizontal distance from the door and window frame is not less than 3m, and the horizontal distance from the exhaust vent is not less than 5m.
2.3 All kinds of lighting power supply accessories must meet current and voltage level requirements
2.3.1 Requirements for lamps and parts in explosive hazardous locations
Lamps and parts used in explosive hazardous areas shall comply with the requirements stipulated in the "Electrical Safety Regulations for Explosive Hazardous Locations of the People's Republic of China".
2.3.2 Installation and fixing of switches and ceilings
The switch should be installed on the phase line. The screw socket must be well grounded. The metal casing of the facility should be grounded. There should be no joints in the lamp line. The fuse box should be used in the ceiling box. Hanging luminaires weighing more than 1kg shall be fixed by metal slings, etc. When the weight exceeds 3kg, they shall be fixed on the embedded hooks, bolts or main keels.
2.3.3 Installation of concealed lamps
When laying the wire in the place where the combustible material is decorated, it should be worn with metal casing, flame-retardant hard plastic casing, and the junction box should be installed at the transition. When the casing is over 30m long, the cable box should be connected in the middle to protect it. When installing concealed luminaires and installing special large hoisting luminaires in important places, the same type of “testing samples†should be made before the full installation. After the verification is correct, the professionals should be fully installed.
2.3.4 Reasonable control of electrical lighting
The lighting currents have their own branch circuits, and should not be connected to dust explosion-proof and fireproofing standards. They must not violate or contradict GB. There are two sets of current engineering design standards. One set is directly translated and converted by IEC standards (standard number GB10000). Above), in terms of low-voltage power distribution, the standard text system is large, the number is large, the search is not easy, and the English original revision and maintenance period is short, and it is difficult for Chinese to follow up synchronously. The country responsible for this editing work is “National Building Electrical Installationâ€. The Standardization Technical Committee (namely SAC/TC205, commonly known as China TC64), because its content directly relates to personal safety, was directly managed by the National Standardization Administration Committee last year (originally managed by the Standards Department of China Electrical Equipment Industry Association); China has self-edited on the basis of IEC standards (standard number GB50000 or above), the main content is concentrated on "GB50054-95 low-voltage power distribution design specification", and some contents are scattered in other design specifications, its strength is content comparison Concentration, easy to find, has played a big role in China, and will have a great effect in the future, but the age is too long. It has been more than 10 years, and some of the content is outdated. Although the revision work has been started, the progress is very slow. Even if a new edition is published that year, it is still impossible to synchronize with the new IEC standard or follow up in time. Another disadvantage is that the technical content is not comprehensive, not specific, far less than the IEC standard. Therefore, the self-made GB is the main one, and the GB converted from the IEC standard is still a difficult situation that everyone faces in a long period of time.
References 1. Jiang Maizhan combined with the safety performance of outdoor lighting devices, in-depth study of IEC standard electric shock protection and questioned some of the important building electrical installations Section 4-41: Safety protection electric shock protection 3. IEC60364-7 building electrical installations Part 7: Requirements for special installations or locations
5. Jiang Maizhan technical obstacles in the application of circuit breakers with residual current protection and countermeasures
New Progress on RCD Applications Electrical Engineering Application Editorial
RCD--On the influence of DC component on RCD and its countermeasures
9. Electrical Equipment Application (Design) Guide Schneider Electric Co., Ltd. China Power Press In 2006, after the power main switch, each branch circuit was equipped with a short circuit protection facility. In order to avoid accidents caused by overload and heat, some important places and inflammable and explosive materials must also be equipped with overload protection devices.
Non-explosion-proof lighting distribution boxes and control switches are strictly prohibited in Class 0 and Class 10 explosion hazardous locations. The connector should be minimized after the switchboard, and the disk surface should be well grounded.
2.3.5 Strict lighting voltage level and load
The lighting voltage is generally 220V, the supply voltage of the portable lighting fixture should not exceed 36V, and the operation should not exceed 12V in wet areas, and the use of autotransformers is prohibited.
Power outlets below 36V and above 220V should have significant differences and markings. In a branch circuit, the number of lamps should not exceed 20, the civil lighting current should be less than 15A, and the industrial use should be less than 20A. The wire size is determined by the load (each socket is calculated with a load of 2 ~ 3A), and the three-phase four-wire lighting circuit should also be balanced with the three-phase load.
2.3.6 Emergency lighting
In shopping malls, terminals, stations, airports, hospitals, theaters, control rooms, and various large buildings and important workplaces, emergency lighting fixtures should generally be installed in case of accidents. When the power system is not available, it can be processed in time. Carry out an ambulance. Accident lighting fixtures should be located in places prone to accidents, main entrances and exits of buildings, important workplaces, etc., and marked with obvious color markings, so that they can be activated in time for accidents. Accident lighting fixtures cannot be of a slow start type (such as ballast starters, etc.). Accident lighting fixtures should be powered by an independent emergency battery to ensure that the normal power system is properly opened when unaffected.
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