【 Weak current College 】 electrical fire protection and proper use of the instrumentation problems

As living standards improve, a lot of various household appliances into households, the electric fire has become the main social fire accidents causing factors. Not only occurrences of electrical fires, and loss, has led to hundreds of inhabitants of fires are high, and the firefighting agencies, quickly and accurately identify the cause of electrical fires, is an important duty, it is also a serious challenge. The author according to the years engaged in fire prevention and fire cause investigation practice and research, and current electrical fire investigation should be strengthened and that a number of issues, summarized on how to use electrical instrumentation on the superficial view point.
1. electrical fire protection is correctly identified the cause of the fire
Compared with the General scene of the fire, the investigation site as timely as possible prior to the effective and full protection of electric field and full access to the original position is very important. I think to do the following:
1.1 correctly grasp the electric fire scene evidence distribution has extensive features.
General Electric fire power to low-voltage transformer → General → fractal power strip power strip ¡ú household switchboards → electrical appliances such as solenoids and distribution equipment; its main line of the power supply line (overhead or underground line) → extension → branch line → indoor cabling → electric (above also depending on the circumstances and large). Its characteristics are: line distribution distance long, links, and control, multi-level protection switch is often. Due to the characteristics of electric energy transfer, in the event of an electrical fire, in an Association of all aspects of the equipment and lines will leave marks or evidence. Therefore not only burned down and the fire spread affected premises wiring, switches, fuses, circuit breakers, electrical facilities to the scene, but also for fire unswept but with the supply of line, control, protection and measurement devices also include on-site in a timely and efficient manner, the scope of protection to finalize the fire cause will play a crucial role. For example the actual met in, resulting in the fire of electrical devices and severely damaged parts in the basement, and power control switch on the first floor of the good; and if leakage point in a building of the line, because the electrical connection to grounding too hot (fire) and burnt areas in buildings b; then as grounded electrical failure point in the high-voltage power distribution section, due to the Earth, caused by the low part of over voltage insulation breakdown caused by the fire.
1.2 electrical fire scene evidence has a tiny, invisible, it is difficult to find.
Electrical fires are often due to a short-circuit, serious over load, leakage, bad, and so produce high-temperature, electrical discharge (ARC) fire, because of the energy release characteristics cause failures revealed these points in the geometric dimensions, small surface area, combined with the effects of the current power supply line uses the wall or decoration of concealed within a layer, a fire in the building and decoration layer of collapse fall easily to the point of failure in melting, discharge, over-current traces of devastating loss, makes a direct electrical fire proof material evidence is difficult to obtain, so be careful in the exploration of the scene carefully, to find such evidence in fire protection should also pay attention to the scene, it is possible to make full use of flowering, spray gun, so as to avoid the loss of material evidence.
1.3 electric fire is affected by several factors.
Electric fire from the fault to the fire were able to show a gradual process. Fire General and electrical design, installation, use and maintenance of multiple links. To accurately identify fire cause and on the fire, the development of logical description must have a comprehensive understanding of all aspects of the situation, through design, installation and maintenance staff to learn more about mastery of electrical design, installation, maintenance, construction drawings, peacetime reconstruction, in particular fire before the use of electrical facilities, the failure condition. Particular attention to the same building, same line users also need to understand the situation.
2. proper use of fire detection equipment is recognized as an important means of fire
How to use existing at the scene of a fire apparatus and equipment to help survey and analysis of fire cause determination, it is the scene of a crime scene investigation. Many fire investigation officer that fire of electrical facilities, equipment, lines have been subjected to serious damage detection equipment is not available. But I think in the proper use of the instrumentation can survey the electric fire to help. In particular, the current electrical circuits commonly used copper-core cables, because of its higher temperature fuse (1083 ° c), the mechanical strength is far higher than aluminum wire, a considerable part of the scene of the fire was burning, drop lines, La, snapped cable is less, the more testing instruments in use provides basic conditions.
The following basic detection equipment and the use of points:
2.1 insulation Tester (a megohmmeter) — — a is available through the measuring phase line power supply line and the line, between the line and neutral line, the line between the protection of the line, the line and the insulation resistance between the Earth and the on/off, to help determine the short circuit, Earth, such as break failure of line, and then along the fault lines look for the point of failure and the corresponding might be a fire of a short circuit, overload, leakage, etc. The second is for transformers and ballasts, motor, household electrical equipment insulation of internal circuits are tested to determine whether the equipment failure caused the fire. Even you can also use the carbonization wood insulation resistance measurements, help determine the fire site or leakage points.
2.2 avometer-a measurement of the scene in a more complete control, protection, and other power distribution equipment to pass or not, to determine the device state at the time of the failure; the second is the measurement of electrical devices internal lines to pass or not pass and resistor size to determine if the device had a short circuit, overload, fault; the third is the measurable device components are subjected to electrical damage, such as capacitors are insulation breakdown, whether thermal breakdown of semiconductor devices, etc.
2.3 magnetic detector — through on line near Pong and suspected lightning point near Pong stray magnetic material and magnetic measurement of, use of magnetic data, rules of law help determine short and lightning fires.
2.4 Vernier caliper — through wiring, fuse diameter measurement, to distinguish the short-circuit protection device functionality.BR > 2.5 plug gauge — no residual fuse, measured fusing clearance to determine the size of the fuse to infer short or over load protection functionality.
2.6 grounding resistance measuring instrument — over the wire connector or fixed contact resistance measurements, to determine the existence of bad cause a fire.
3. concluding remarks
With modern electric products in bulk and electrical wiring, equipment, fire protection measures for improving the electrical fire investigation of the degree of difficulty are increasing, in addition to the above discussion, in the field of electrical fire material evidence and identification of the material evidence of fire, common lab insulated conductor short-circuit, over load, leakage, etc., by the mechanism of the fire, as well as how to combine actual situation, to identify the causes of fires and proper representation, and so it remains to be strengthened and improved.