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Matters need attention as distribution main cable

Information Source:Henan Huadong Cable Co., Ltd Release date:2014-02-26

1 the laying of cables to keep distance

Electrician in a chemical factory inspection duty and low voltage power distribution room, found a flashing light in cable trench, near to check and found no abnormal phenomenon, but when leaving the scene after the explosion and fire, cable trench, ditch hundred cable burned,The cause of the accident cardiac cable trench lye infiltration, but did not pay attention to, although the XLPE cable corrosion  but this cable and corrosive liquids contact, causing the outer insulation breakdown, when the sewage pump motor operation was burnt while protecting device fails to cut off power source, due to short circuit current cable heating sewage pump motor insulation breakdown, explosion, the cable in cable trench destroyed the same event to occur in the Shanghai Univer. The students three buried cable  dormitory because one insulation damage caused by short circuit explosion, the explosion caused by heat from the other two underground cable insulation is damaged and explosive cable, the construction specification minimum net distance is 0.1M (GB50168 92), but is often limited by the environment, can not reach, but must have at least 1D (D for the cable outer diameter) spacing, the aim is to ensure the cable of a cable fault occurs is not affected adjacent. But this stipulation is neglected in the cable trench or bridge in the laying of cables, cable not only close together laying  and overlapping 2 ~ 3 layer  in this case, if any one cable short-circuit explosion, will make the next to the other cable together was the same results in Moscow Ostankino TV Tower and the Eiffel Tower into the fire, is a cable to cable caused by short circuit around. In addition, China's Baosteel three converters and production, but also laid in cable short circuit caused by.
According to the survey, the current project, almost all cables in cable trench and tray are close together laying, each cable short circuit accident guarantee in this case  anyone not; once one cable short-circuit accident occurs, the consequence will be inconceivable for such a grim situation, some designers take negative method: reduce cable current carrying capacity (with a maximum of 70%), but did not prevent the user from electrical equipment increases the current carrying capacity of cables, and even the use of full load. Even if the electrical equipment users according to the design requirements, the cable works in light load condition, but as long as the electrical equipment fault, the cable is still possible work overload situation. Another method is the use of reliable protection device manufacturers, once the cable overload or short circuit occurs automatically cut off the power supply, which is set up in theory, but can not guarantee protection device is reliable, any electrical device has the possibility of damage, fires often occurs in electrical apparatus function failure case

2 cable fire prevention measures can only control the fire did not expand to another area

A fire retardant coating and fire blocking material two kinds of cable fire prevention measures. When the cable is fire, fire retardant coating on the surface of cable fire baking and expansion, reduce the flame on the cable invasion; fire blocking material for blocking holes between floors, when the cable through the floor, the residual pore with a fire blocking material blockage, can prevent the flame from a floor hole down to another floor.

A fire retardant coating and fire blocking effect of the material: fire prevention measures for cable only prevent external flame on the cable invasion, and on the cable itself is not to stop burning effects, therefore, if the Cable Fireproofing and fire blocking material can prevent the cable fire is wrong cable from the fire the angle can be divided into three types: ordinary cable, flame retardant and fire - retardant cable. The insulating layer and the skin will burn at high temperatures common cable, and can not be self quenching; flame retardant cable will also burn  but in external flame gone Zixi; refractory cable has two levels: a class can work under 1.5h at 1000 ℃, 850 ℃ can work under B 1H, fire will not burn, but the more expensive price, distribution sites are not allowed to fire power fire resistant cable. Any a tower or high-rise buildings are not all used in fire-resistant cable, electrical design of buildings usually choose section have some cable margin, but put into use, users often ignore the design capacity, access to a lot of electric equipment, and the cable overload. In many cases, although the total capacity of the power supply is adequate, but fail to consider the three-phase equilibrium, so that a phase overload is a common thing, therefore, when the electrical equipment or line fault occurs, cable has the risk of burning.

3 distribution lines should adopt the busbar

Replace the cable with steel shell bus slot, which can eliminate the cable fire will ignite the surrounding combustible fire hazard. Using air or hybrid bus slot, if the bus slot due to overload or short circuit, insulating layer bus caught fire, and will not ignite the combustible busbar around, but the air type or mixed type bus slot has a chimney effect, high-rise buildings, once the fire, air type or mixed type busbar encourages the spread of fire smoke. The dense insulated busbar to the chimney effect drop very low, but the ordinary bus slot does not fire, once the fire, affecting busbar will cause outages. The South Korean subway fire caused major casualties, is mainly caused by power failure. Common busbar not waterproof, as long as there is a section of busbar busbar cannot send water, electric, and to the tens of busbar to find water bus slot, and the workload is great. Shanghai Pujiang cross-strait two famous high-rise buildings have occurred because the water into the bus groove causes the cable cannot send electrical phenomenon, then the bus slot installed down 1 / 3, to find the bus slot damp, resulting in duplicated construction greatly. Refractory bus slot steel shell, mica insulation can fire, but also afraid of the water, even if there is no water in the construction, once the fire, the fire will also cause the refractory bus slot short-circuit interruption, busbar, refractory bus slot at least has the anti water function to have practical value by what type must be cautious, not only must choose good products, but also to understand the manufacturing plant

4 selection of busbar should consider the following aspects from the angle of quality and performance:
(1) to prevent the possibility of bus short circuit, ensure that the power supply is not interrupted by a bus fault;
(2) strong overload capacity;
(3) flame retardant and has a certain fire resistance performance.

Huadong Cable Co. Ltd. produced no shell closed busbar, with intensive and double insulated busbar advantages, bus insulation performance is very excellent resin as an insulator, above its voltage capacity can reach 5000V; because of the distance between the bus, bus comprises a connecting head with all the cast resin, therefore even if the bus burr, also won't bursting resin insulating layer of short circuit, the busbar without shell, so the circuit does not occur between phase to the. Because of the closed shell protection grade IP68, meet the requirements, moisture can not enter the bus slot, so the bus slot to allow long-term immersion in water, even in the long-term use in corrosive environments. Resin can the busbar is adopted to ensure no cracking in the below 50 ℃, able to withstand the impact of more than 5J, so no metal shell.

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