subject: Qiao Prevent Electrical Fires, Heavy Duty Low Voltage Electrical - Low Voltage, Electric Fire - [print this page] Fire from the situation in recent years, cause of the fire are: electrical, fire accidentally, illegal operation, playing with fire, smoke, fire and so on. Since reform and opening, with the rapid development of national economy and people's living standards increase year by year, all electrical equipment and appliances increased sharply the amount of electrical fires soar as a result, according to fire department statistics, electrical fires account for 25% of the total number of fires, among the various types of fire first. See more exciting information
I. Electric Fire and technique measures at home and abroad
1. Lead to the main fire which?
Fire from the situation in recent years, cause of the fire are: electrical, fire accidentally, illegal operation, playing with fire, smoke, fire and so on. Since reform and opening, with the rapid development of national economy and people's living standards increase year by year, all electrical equipment and appliances increased sharply the amount of electrical fires soar as a result, it was Fire Department of Statistics, the total number of electrical fires account for about 25% of the fire, among the various types of fire first.
2. Electrical fire According to fire department and an expert on-site inspection of electrical fire statistics, fire electrical fire about 60% of the electrical short circuit, short circuit fire, due to leakage caused by ground fault produced the great majority of fires, it is the most common electrical fire.
Power lines and equipment for some reason, such as improper installation, the aging or mechanical damage and other reasons, the insulation performance degradation, leading to power lines and equipment between the earth and there is no normal current flow through it is the leakage. So that part of the earth leakage current flows, resulting in Energy Waste; human contact failure caused by voltage electric shock, a life-threatening safety; insulation damage caused by ground faults that may occur electrical fire. The so-called ground fault refers to short-circuit live conductors and ground.
Electrical lines and equipment damaged by a ground fault isolation, and electrical conductivity in the leakage point of failure will lead to bad joints arc, electric spark, which arc of great resistance and voltage drop, which limits the fault current, so too Current Protector Can not move or can not timely action to cut off power supply, and generate hundreds of milliamps of leakage arc over the local high temperature above 2000 , is enough to ignite surrounding combustible material and cause electrical fires, the electrical hazard, the ground fault than generally greater danger of short circuit.
In addition, there are some deep-rooted factors, fire codes limit the provisions of the electrical fire less, supervision and management is not enough, the people lack knowledge of electrical safety, resulting in a large number of users of electrical design, construction, use there are many hidden dangers. Therefore, the establishment of electrical fault fire warning system is particularly necessary.
3. Abroad to prevent leakage of technical measures taken by the fire
Developed countries attach great importance to the prevention of electrical fires, according to information reported consumption in Japan is China's eight, but only its electrical fire about 3% of the total number of fire. Japan has been able to effectively control the electrical fire, electrical materials and construction in addition to its good quality, strict implementation of the electrical design and management in place, the one very important reason is the widespread application of the leakage-line detection. Japanese national standard "insider point of order," which stipulated the need to install fire alarm leakage sites are:
1) collection of important cultural heritage, an important national data Records, an important cultural property, buildings, important works of art collection of buildings;
2) greater than 150m2 of hotels, restaurants, apartments, public housing, etc.;
3) greater than 300m2 of theater, cinema, exhibitions, bars, nightclubs, shopping malls, hospitals, etc.;
4) greater than 500m2 of schools;
5) greater than 1000m2 warehouse; Have parking, airports, multi-fire construction. Leakage circuit breakers and electrical leakage detection alarm fire is supporting the use of former installed in the loading terminal, for the protection of personal electric shock, which is installed in the power unit Transformer Low pressure side of the grounding line or Distributors Division, testing electrical systems or Link leakage current, such as more than alarm set value that is used to prevent electrical leakage caused by major accidents, and electrical fires. Combination of the two constitutes a leakage, "the overall monitoring, local trip," a complete protection system. Europe and the United States is also widely used technology to detect power lines and equipment insulation condition, a test line between the arc of the instrument has come out, which greatly reduces the possibility of electrical fires.
4. China's current electrical fire prevention technology measures taken
Popularity in China is now a leakage circuit breaker (also known as residual current operated circuit breakers, earth leakage protection switch), it is relatively leakage circuit by the residual current exceeds the set value can be automatically cut off power protection device, Its main role is to prevent people and livestock electric shock, electrical fire protection also has a role. In order to reduce casualties and reduce the physical shock ground fault when the blackout cut off power supply range, usually in the supply line installed at different locations in different capacities leakage circuit breakers, the formation of graded protection. According to electricity load and line conditions, more than three-stage protection.
However, the three are used to protect leakage circuit breakers have their limitations, that is:
(1) security and uninterrupted supply of contradictions
Leakage circuit breakers and smaller action current set value, the better protection, but the uninterrupted power supply and poor, the scope of this level of protection is limited. Action current settings to increase, uninterrupted power supply improved, but the safety down.
Leakage circuit breaker as Transformer Processing difficulty, the performance is often unsatisfactory, some product malfunction occur, resist movement, grade trip phenomena, that is why there are three levels to protect power lines but still frequent causes of electrical fire, which limits its use.
Over rated the event of leakage power is cut off, causing heavy economic losses due to power failure and adverse social impact of electrical installation or premises is not allowed to install leakage circuit breakers. For example, public places, emergency lighting and fire power, there is such as the Great Hall of the front door and other important buildings.
(2) I do not know the specific circumstances of leakage The role of electrical leakage
circuit leakage is a serious cut off the power when it can not detect low leakage current, leakage current size, can not understand the changes in the state of the circuit insulation, will not be able to forecast the electrical fire.
(3) harmonics can not run to electric leakage breaker
Power system harmonics is defined as the periodic non-sinusoidal power to Fourier
