Analysis of student housing distribution system and the danger of leakage prevention measures

Abstract: Student apartment distribution system leakage hazards mainly leakage current and the voltage generated can cause a fire, that leakage is still a major electrical fire caused one of the reasons and preventive measures put forward the technology leakage.

Thesis Keywords: apartments, low voltage distribution system, leakage hazards, prevent
Throughout the University Student Apartment main causes of electrical fires: short circuit, over load, poor contact, leakage, lighting and electric appliances such as ignition fuel. In recent years, caused by the leakage and short circuit caused the fire continue to occur, and by the leakage current The fire caused more invisible, often quietly, after a fire is difficult to find out the real reason, is often overshadowed by short-circuit is difficult to prevent such an illusion, therefore, the greater harm. fully understand the risk of leakage of the fire and take active measures to prevent leakage of electrical current fire safety should be an important task.

When the electrical lines and electrical equipment insulation damage caused by ground faults, mainly refers to the phase to ground or between conductors linked to short-circuit, including the phase and earth, PE line, PEN lines, power distribution and electrical equipment, metal, iron bed apartment, apply line steel, bridge trough, building metal structures, the upper and lower water, and heating, ventilation pipes and metal roofing, water, etc. The asked the circuit. When a short circuit in the ground ground fault sustained period of time, with its associated electrical equipment and conductive parts of the exposed pipe and fittings on the ground outside the fault between the conductive part of the voltage. This voltage allows personal subjected to electric shocks, but also because of the land arc or spark a fire or explosion, to schools and students have serious life and property losses.

l danger of leakage
Electrical lines or equipment insulation injury, in a certain environment, near the material (iron beds, iron clothes, iron, study tables, threaded metal pipe, metal electrical installations, damp wood, etc.) leakage occurs, as water leakage moisture or water to the local material, as the local material leakage can live, will give people cause serious or fatal electric shock or sparks, arcing, overheating, etc. and cause a fire. Currently, students in the use of apartment distribution system access to zero protection (ground fault protection) and over current protection device (circuit breaker, etc.) to prevent serious leakage circuit to happen.

1.1 The issue raised
Leakage occurs when the electrical equipment that touch the shell short-circuit, the current device shell, protect access to the zero line (protective earthing) the zero line (the earth) form a closed loop, leakage current is usually large, which makes circuit breakers cut off the power, it seems that the risk of leakage can be avoided. However, due to the presence of the following reasons, the over-current protection device is not absolutely reliable.

1.1.1 circuit breaker several times the size may artificially increase the adhesion or arc, would not achieve over-current protection function, 1.1.2 electrical fault may occur far enough in the end of the system, fault loop impedance greater not enough to short-circuit current leakage circuit breakers, electrical equipment if the larger capacity 1.1.3, melt leakage current than the rated current of the circuit breaker will not move, does not meet the requirements of 1.14 grounding, resulting in ground resistance larger, leading to short-circuit current leakage circuit breaker will not make small moves, 1.1.5 when using over-current automatic protection switch, switch failure, or tripping current setting is too large, automatic protection switch does not move, 1. 1.6 Protection of access to zero (ground) wire terminal connections are not real, resulting in contact resistance is too large, limiting the fault current, causing circuit breaker does not move, 1.1.7 Electrical fault may occur in contact and from the system control false end more remote, not enough to short-circuit current transient leakage circuit breakers, 1.1.8 Intelligent control of power can not effectively control (main control boards, cell board, or the over-current and other factors being struck by lightning damage to electronic components).

Leakage in the actual fire, or the existence of one or several simultaneous attention and not be so in the event of leakage, will persist, resulting in electric shock or electrical fire accidents, fires, many of leakage also proved this point. This article will This highlights the dangers of leakage and fire prevention measures.

1.2 leakage causes harm
1.2.1 leakage fault point contact will be false, it may take non-connected arc occurred, and false contact resistance contact with the larger cause, so over-current protection device will not operate, while arcing fault at higher temperatures, according test, only the current arc 0.5A up to 2000 ~ C above the temperature sufficient to ignite all the fuel .1.2.2 protection or the protection of neutral ground of the small diameter of choice, when leakage through the larger current, the line temperature rise faster, also can cause a fire .1.2.3 in wet conditions, when the live contact with bare wires or other wood fiber products, the leakage current flowing through it when wet cellulose, wood will and Fiber Products carbonized into fire. This reminds people not to wear electrical circuit through the fuel pipe protection when it is very dangerous, the danger of such leakage is present in all of the distribution system .1.2 A terminal at the connection is not solid, causing the fire. phase with the zero line virtual terminal line access or protection terminal connection is not real, difficult to find fault, in the event of leakage, because the point of failure is too loose or corroded connector, etc., with high resistance, resulting in local overheating, connecting terminals at high temperature or arc can ignite surrounding combustible material or burn electrical switches, sockets, connectors, lines, ignition cable wooden base and is a more common form of leakage fire. Only in November 2009, March 2010 distribution panel in a university student apartment fire twice, for example, before the fire, it is low power consumption apartments, most of the students have been closed, the load at a low state, when the fire occurred, lighting, electricity is still normal. The investigation, the total air distribution switch box severe charring, protecting the zero line terminal melting metal concave mark, in line with the leakage, because the fire did not occur in time .1.2.5 leakage power voltage caused by leakage of fire continues to occur, due to the current can not be dispersed, while looking for another loop through the small resistance, the will to protect access along the zero line (ground line) transmission so that all electrical installations connected to ground voltage with a metal casing, this time may be low potential to neighboring plumbing pipes, gas pipes and other metal components arc into the fire source voltage of only 20V can be made to maintain a continuous arc occurs, the same can ignite surrounding combustible materials. This shows that, due to the conduction voltage, leakage current points and fire points are not necessarily consistent. Links to Research Papers Download http://www.hi138.com l. 3 factors that have leakage
Produce leakage of factors, mainly the following:
1.3.1 Installation of Low Voltage Distribution System more than a non-electrical professionals, uneven quality, quality is difficult to guarantee, in: humid or corrosive environment, pH, wires for surface, equipment, protection of mounted directly without making , 1.3.2 install wiring, knives, pliers, hammers and other damage without making the timely processing of insulating layer, 1.3.3 installation is not standardized, wire connectors and insulation wrapped connection quality does not meet the quality requirements, 1.3.4 electric line or equipment failure in a long time due to overload or cause of insulation deterioration and longer life ,1-3 .5 Non-national standard used counterfeit, inferior appliances 1.3.6 external factors: moisture Baptist people, wet , Corrosion, Extrusion, rat bite, etc..


Two leakage prevention measures
2.1 Practice for low voltage electrical installations in strict accordance with Law, non-electrical professionals will be allowed to posts, adhere to the regular check and maintenance to prevent leakage of the various human factors generated.

2.2 The strict implementation of <<Electrical installation specification>> <"Architecture and interior decoration design for fire protection>> as far as not flammable combustible materials, when the electrical circuit through the fuel, wear flame-retardant rigid metal pipe or plastic pipe protection prevent leakage, the use of metal tube wiring, be sure to prevent insulation from being damaged. power distribution equipment (switch, socket, distribution box, etc.) and electrical equipment and flammable materials should be sufficient to maintain a safe distance, indeed inseparable, heat protection measures should be prepared.

2.3 The installation of leakage protection in the current set of distribution system and over-current protection device protecting access to zero and other measures can not effectively prevent the occurrence of fire, leakage, therefore, the total supply in the building should be set into the line of dedicated leakage protection .96 fire in the implementation of the International <<low voltage power distribution design specification "> this also made more specific requirements. In order to prevent blackouts in the power distribution box and the user total control boxes should be set separately leakage protection and its rated operating current and rated operating time to be a reasonable match to make a classification of protection functions.

2.4 Protection measures to protect the access and protection of ground zero cross-sectional area of selection must be calculated to determine and check with touch Shell short-circuit current. The terminal connections must be reliable, does not allow loose and frequently check the quality of their connections.

2.5 Grounding resistance should meet the design requirements for electrical equipment protective earth resistance should not exceed 4n, such as larger capacity of electrical equipment, melt fuse current is large, should increase the ground wire to the grounding section or parallel fully reduce the grounding resistance and increase the leakage short-circuit current, is conducive to protective devices.

2.6 The implementation of the equipotential leakage protection circuit for single-phase 220V only question then contact protection, there is also a result of mechanical wear, poor contact, the quality factors of instability caused by short-lived actions such as failure of the various problems, not Individual protection measures as a reliable, so there should be implementation of the equipotential bonding in order to effectively eliminate the leakage of electrical lines or equipment and low voltage arc between the metal components, spark generation, which caused the fire to eliminate the possibility of leakage voltage . equipotential bonding is to protect access to zero bus and the building water main, the total gas pipes, heating pipes and other metal pipes or devices connected by wires measures to achieve the objective of a balanced potential in buildings, especially for inflammable and explosive places have their irreplaceable role
2.7 Installation leakage alarm system installed in the low-voltage electrical line leakage alarm is ~ kinds of effective preventive measures. Through leakage alarm system that can accurately monitor the electrical circuit faults and abnormal conditions, early warning that leakage problems, reported immediately reminded officers to address these risks, to avoid leakage for the national economy and people's lives and property caused huge losses, the residual fire in the bud.

Conclusion
Low voltage distribution system through the student housing norms set, so that student housing and low voltage distribution system protection more complete. And smart communication interface low-voltage power system control and fire alarm system network operation, to achieve the dual alarm and control functions, will be prevent leakage hazards inevitable. As applied to prevent leakage in the current design of harm, or a new topic, although the state has put a higher demand for its specification, but the leakage prevention system is now in its infancy stage, more or existing products on the market There are some with less specification, design, incompatible with the process issues, but as technology advances, I believe that these issues will be resolved soon, to better serve schools and students to defend the lives and property. Links to Research Papers Download http://www.hi138.com