Low Voltage Distribution System Leakage Study Of Hazard Prevention Measures

Abstract: Introduced low-voltage distribution system leakage current and voltage

generated due to Fire The danger of leakage of the low voltage distribution system led to Electrical Fire Reason, given the technical measures to prevent leakage.

Keywords: Electric Power Distribution System Leakage Leakage Leakage Protection Systems

Electrical fire caused major reasons: short circuit, overload, poor contact, leakage, Lighting And electric appliances such as ignition fuel. In recent years, caused by the leakage of fire continue to occur, such a fire than the fire caused by short circuit, and covert. After the fire is difficult to find out the real reasons (such as false overshadowed by short-circuit), therefore the greater the danger, fully aware of the danger of fire, leakage, leakage of technology to enhance prevention, electrical safety is one of the important tasks.

1 risk of electric fire Electrical lines or equipment insulation injury in certain circumstances near the substance (threading metal pipe, metal electrical installations, damp Timber Etc.) will happen leakage, leakage of local materials could live, people will have serious or fatal electric shock hazard or produce sparks, arcing, overheating caused by high temperature fire. Currently, low-voltage distribution systems use access zero protection (ground fault protection) and over-current protection device (fuse, etc.) to prevent serious leakage short circuit occurring.

I.1 Technical Analysis of leakage occurs

Leakage occurs when the electrical equipment shell that hit short, the current case so that equipment, protective zero line (protective earthing), the zero line (the earth) form a closed loop, leakage current is usually much, will fuse action and cut off power supply, this would seem that the risk of leakage can be avoided. However, the presence of the following reasons, so that over-current protection device is not absolutely reliable.

(1) Fuse specifications may be artificially increased by several times or fuse Copper Silk substitute, will not achieve over-current protection function;

(2) the point of failure may occur far enough in the end systems, fault loop impedance greater leakage short-circuit current not enough to fuse action;

(3) If the electrical capacity of a larger rated current than the melt leakage current, the fuse will not move;

(4) grounding device does not meet the requirements, resulting in a greater grounding resistance, resulting in less leakage short-circuit current fuse will prevent the action;

(5) When using over-current automatic protection switch, the switch failure, or tripping current setting is too large, automatic protection switch is not action;

(6) protective zero (ground) line terminal connection is not real, resulting in contact resistance is too large, limiting fault current, causing fuse does not operate.

This phenomenon is not uncommon in practice, or the presence of one or several at the same time there was great importance without leakage in the event, therefore, will persist, resulting in electric shock or electrical fire. Many cases of electric fire also proved this point.

1.2 Leakage-circuit causes fire (1) the point of leakage fault current leakage caused by poor contact or fire. Usually the point of contact failure does not really, like access non-connected. Lead to higher contact resistance, so over-current protection device is difficult to move; the same time the point of failure will occur at the arc, it was measured only 0.5A of current arc temperature can reach 2000 or more, enough to ignite all flammable materials.

Protection or the protection of ground zero line of the diameter size of the easily overlooked, if you choose too small, when adopted by a large leakage current, the circuit temperature rise faster, also can cause a fire.

(2) protect the zero line or the protection of ground terminals connected in the office is not real, cause a fire. Protect the zero line or the ground terminals for connecting false, resistance too. Equipment can work as usual, but the trouble spots not easily found. Here the event of leakage, high resistance occurs, resulting in local overheating, the connection terminal in place to produce heat or arcing can ignite surrounding combustible material, or burned electrical socket, switch, ignition wood base. This is the more common form of leakage fire.

(3) leakage voltage and leakage of fire continued to occur, because the current can not be dispersed and find another the same road leads to a small resistance, the will to protect access along the zero line (ground line) transfer all the electrical devices connected metal shell with a point-to-ground voltage may be near the low potential to plumbing pipes, gas pipes and other metal components arc into the fire source. Only 20V voltage to maintain a continuous arc can make happen, the same can ignite surrounding combustibles. If the gas tube arc, the wall may breakdown, causing a gas leak caused a fire. Be explained is. As the voltage of the transmission, leakage point and fire point is not necessarily the same. The factors that cause leakage

l.3 Causing leakage of factors, summarized in the following:

(1) the installation of low voltage distribution system and more by non-electrical professionals, uneven quality of personnel, difficult to ensure quality installation, such as: pH in wet or corrosive environment, the wires out dressing, equipment protection without making direct installation; Wiring , The knife, pliers, hammers, cable insulation damage; wire wrap connectors to connect the quality and the quality of insulation does not meet requirements, and so abnormal phenomena.

(2) negligent in checking electrical circuits or equipment. Overload or due to other reasons, long service life of insulation aging:

(3) use of counterfeit, counterfeit electrical products;

(4) external factors: the line or equipment by water immersion, squeezing, rat-bite so.

2 leakage of fire prevention measures

(1) low-voltage electrical equipment installed in strict accordance with operational procedures work, non-electrical professionals are not allowed for employment, to prevent leakage caused by various human factors.

(2) shall be strictly enforced " Building Internal Decoration Design Fireproof Standards ", do not minimize the use of flammable or combustible materials. Particularly when the electric circuit through the fuel should wear flame retardant rigid metal pipe or plastic pipe to protect it as a good plastic insulation can effectively prevent leakage. Metal tube wiring, be sure to prevent damage cable insulation. Distribution equipment (switch, socket, distribution box, etc.) and Electricity Equipment and enough fuel to keep a safe distance, indeed inseparable, protective measures should be well insulated.

(3) the installation of earth leakage protective device, the existing low-voltage distribution system will be installed in the general leakage protection switch. Leakage protection switches single-phase and three phase. Single-phase leakage protection switch for home Illumination . Leakage protection switch three-phase switch into the air leakage protection feature been made to. The switch with overload, short

by: gaga

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