【 Weak current College 】 large and medium-sized supermarket fire safety management measures

1. electrical line should meet the electrical safety and long-term load development requirements

1.1 calculation and select wire cross-section

The electrical design specifications are required in the choose when the conductor wires containing flow must be greater than the load current, but some factors often inadvertently leave a fire hazard.

(1) wire different laying (such as the downlead and concealed; wear noncombustible protection and wear galvanized pipe protection, etc.), its thermal conditions are different, depending on the circumstances of the current fixed wire;

(2) conductors of ambient temperature correction: wire to the ground, underground or laying in the air will be subject to the annual average temperature of warmest month increased by 5 ° c to correct its allowed current-ratings of the parallel laying; allows current should be calibrated by tie; on the ceiling (close top) temperature correction should give special attention, in wire and cable section select the configuration you can increase the level and, at the made other design jobs, ensure good ventilation within the ceiling;

(3) should consider the possibility of increasing power consumption.

In electrical design depending on the circumstances, the conductor cross-sectional area of the appropriate zoom level 1-2, which increases the investment, but in the long run, but it is.

1.2 line laying

Power cable and signal wire should be laid, when the power cord must be parallel to wear metal pipe or armoured cable; line laying to make full use of concealed, need downlead should pay special attention to the choice of the electric wire electric cable and the laying of the way in ensuring fire safety partitions not thereby compromised; line should maintain a certain level the heat source and vertical distance.

Wire, cable's selection:

(1) selection of copper-core cables as possible, avoid using aluminum conductor lines;

(2) must be in accordance with the requirements of electrical circuit fire retardant, choose to use fire or fire-wire, cable. This not only from the electrical lines, better prevention of fire, and be better able to ensure that fire is fire power of electricity reliability and security.

2, the perfect room for internal and external lightning intrusion system

Room lighting focuses on preventing the invasion of lightning. Lightning by Lei lightning currents generated strong electromagnetic fields and the conductor induction over voltage, over current formation of lightning. Based on national standards for the building mine design code GB50057-94 (2000 version), for lightning protection design, in order to prevent lightning waves from signal cable or communications line, you must access the device signal cable and communication line interface, power lines, and other ports with the corresponding surge arrester, to limit the lightning produces high voltage, thereby protecting the safety of the device. Computer room cabling cannot be laid along the wall to prevent lightning walls reinforced strong instantaneous transmission of lightning current, magnetic induction in the engine room the line and the device is striking.

In addition, attention should be paid to the choice of reliable quality, good performance, energy match proper surge arrester and professionally installed.

3, power supply unit earthing design

According to the power unit of the technical requirements and the region's geography, geology, take different measures to the most high performance price ratio, as far as possible the introduction of new technologies and new materials to the design resistance of the Constitution: the grounding resistance is determined by the grounding wire resistors, grounding, grounding surface and the soil of contact resistance, beginning from the grounding to the distant (20m) diffusion current the path soil resistance, i.e., bulk flow resistance.

Reduce the resistance of the main measures: grounding resistance in the first two parts of the grounding resistance ratio smaller, decisive is the contact resistance and bulk flow resistance. They reduce the grounding resistance from both parts of the work, may be the best grounding planted depth, length grounding technology and chemical resistance-reducing agent, and other technologies to reduce contact resistance and bulk flow resistance.

3.1 vertical grounding of best burying depth

According to the formula: R = p/2 p r = π-π/2 L (p is the soil resistivity, L for vertical grounding of burying depth) is visible, R and L inversely, to reduce the R, L, the larger the better. But the type partial differential: aR/aL = π-p/2 L 2 available: when increasing L to a certain extent, reducing resistance rates aR/aL approach zero. Therefore, the design should press ground grid equivalent RADIUS,

Geological situation in the region to determine the General take 1.5-3.5m suitable.

3.2 long grounding techniques

Usually in the grounding network, each single grounding laid spacing, equal to the length of a single grounding for two times, when the current flows when the single grounding by restraint and prevent current circulation that is equal to the increase of the single grounding bulk flow resistance, this impact current drift phenomenon, known as the masking effect. Can not wait long grounding techniques, that is, the length of the vertical grounding are equal. In the grounding of the layout, arrangement taken as vertical grounding for two long short or a long two short so that grounding group of shielding effect reduced to a minimum.

3.3 use chemical resistance reducing agent

Resistance-reducing agent itself is a good conductor, will it be used in grounding and soil between, on the one hand, and the metallic grounding in close contact, reduce the grounding and soil formation of contact resistance, sufficiently large current flow cross section; on the other hand, it can be to the surrounding soil permeability and reduce soil resistivity around in grounding a variation of low resistance area, lower contact resistance and bulk flow resistance has a significant effect.

4. appropriate use of temperature sensor cable type temperature measurement system

Because the engine room the cloth has plenty of power and signal line, monitoring to track the temperature to prevent abnormal fire is important. A temperature sensor cable type temperature measurement system for cable temperature online measuringTo keep informed of cable temperature variations, the timely detection of cable faults and alarm. The system has good computer interface, you can display cable channel modeling diagram, display the actual sensor to monitor the location and all the cable type, length, cross section, intermediate connector location parameter, when you run when an exception occurs in the cable, the display and audio, are available through computer cable channel simulation map view directly, and can quickly and accurately determine the actual location of the failure, and improves the reliability of the cable operation and technical management.

5. other considerations

Battery compartment (VRLA batteries excluded) should be used in explosion-proof lamps, installing exhaust equipment, the power switch located in the outdoor power transformer; electromechanical equipment, conveyor belts used motor should be installed in non-burning material, and setting the protection bar; the long-term use of UPS uninterruptible power supply, should inspect their fever, avoid fire and fire prevention measures.

Electric lines, electrical equipment should be installed in accordance with the norms of professional electrician. Lighting lines across the ceiling or other shelter to wear metal pipe laying, connectors, junction boxes to install; the engine room the prohibition of private add confusion, power cord, you need to use a temporary power cables, to double sheath cable. Electrical line shall be crossed or wear one air conditioning ventilation pipe; room is strictly forbidden to

Use-tungsten lights, heat lamps, lighting and fuel distance should be greater than 0.5m. Lamps and ballasts will not install on combustible, flammable materials; the engine shall not use electric furnace, heat appliances. Power transformer should be installed in non-combustible material base, and set protection bar.

6, telecom room should be set up automatic alarm and automatic fire extinguishing device in inert gases

Automatic alarm for use with the smoke or heat probe two functions, can be located in the ceiling, activities under the floor, ventilation pipes, inside of the machine, the power room, tape and disk protection establishments keep spare parts, appliances and communication equipment, etc. At the same time, in the appropriate parts but also additional manual alarm device in order to achieve early detection of fire; automatic fire extinguishing appliances to choose carbon dioxide fire extinguishing system or smoke burnt into the acquisition fire extinguishing system. Equipped with automatic fire alarm and automatic fire extinguishing equipment for computer room, set fire control rooms; there should be no question of private fire power supplies and DC standby power supply, with both automatic and manual trigger. Set the automatic fire fighting facilities of the region, its wall and fire resistance of the door should not be less than 1 hour fire resistance of the ceiling may not be lower than 0.25 hours; air conditioning system with alarm control system with control switch, electric heater and fan with switch to chain control. Pipe through the room wall and floor Office should be located fire dampers, working temperature up to 25 degrees centigrade.