Top cable fire: If you take a look at fire statistics for Germany, one cause of fires has always been at the top for around 15 years: Electricity and especially the cable fire. According to statistics from the Institute for Loss Prevention and Damage Research (IFS), the distribution of fire causes is very stable over time. In second and third place are human error and overheating. Another reason is often outdated electrical systems. Cable fires often start in private homes. Here, in contrast to the commercial sector, there is no obligation to periodically subject electrical equipment to testing in accordance with the DIN VDE standards applicable in the commercial sector.
Cable fire risk – The dilemma of the private sector
Three circuits were a standard in the sixties. One circuit each for the electric stove, for the lighting and for the sockets. In the meantime, however, private electricity consumption has increased fivefold. Although the power consumption of individual devices is declining more and more due to better eco standards, the number of devices connected to the grid has increased enormously since the 1960s.
Old wires& multiple sockets connected in series further increase the risk of cable fire
In many cases, the existing power grid cannot keep up with this development. In order to connect all devices nevertheless, multiple sockets are often used or even connected in series. However, the wiring permanently installed in the building remains the same. Often z.B. in the kitchen toaster, kettle and the coffee machine connected to one power strip. The thin connecting cables of many power strips are overloaded as a result. However, the fuse in the circuit distributor does not break because it is dimensioned for the larger cables in the wall. Socket strips are therefore often the cause of cable fires. Such overloads do not have to result immediately in a fire. Rather, they continually weaken the substance of power lines over time. Excessive currents lead to higher heat loads and these in turn cause the insulation of the cables to become porous. The risk of smoldering fires increases as a result. Smoldering fires in walls can go undetected for long periods of time and then provide an ideal breeding ground for home fires.
Cheap products from the Far East
Another risk factor is cheap products from the Far East purchased on the Internet, which often do not meet European safety standards. Anyone who wants to save too much here quickly plays with their home furnishings, which fall victim to a cable fire, or even with their life. Overvoltage from lightning strikes is also still a risk factor. Especially before a thunderstorm or severe thunderstorm, you should disconnect electrical appliances from the power or use a surge protector, advises the Association of Electrical Engineering Electronics Information Technology. In addition, you should always have a fire extinguisher as well as several smoke detectors in the house. The latter is even mandatory in almost all federal states.
If you look at the individual electrical appliances then here are clothes dryers the front runners among the fire causes. These devices should therefore not be operated if no one is in the apartment.
Source: Damage prism.de
How a cable fire occurs ? or Small cause – big danger
The technical triggers for a cable fire can be assigned to three categories:
- Loose clamp connections
- Cable breakage
- Loose terminal connections
One important cause of a cable fire is loose clamp connections. electrical installations are laid in individual sections. These sections are often connected by clamps. In the event that these terminals become loose, this can result in brief contact interruptions and arcing faults, such as those that can occur in a cable fire.B. are more frequently observed in conductor rails of urban and underground railroads. In the course of the formation of these arcs, temperatures of up to 1000° are not uncommon. The plastic materials used in the installation will burn, and flammable gases and vapors may be produced which can ignite in the further course of the process.
- Cable break
A cable break is characterized by a localized reduction of the cable cross-section. High current densities then occur in this area. This means that a lot of current flows through a reduced conductor cross-section and the cable heats up unacceptably, damaging the insulation. This can lead to short circuits and also to electric arcs, which result in a cable fire.
The thermal overload of a cable is characterized by the fact that the cable cross-section is generally too small, resulting in an impermissibly high level of heating or heat generation along the entire length of the conductor. heat loss occurs. With properly executed electrical installations, this cause can be ruled out, since in the event of an overload, the protective device z.B. a circuit breaker or fuse trips and interrupts the power supply. Cable cross-sections and their permissible continuous current load depend, among other things, on the conductor material used, conductor cross-section, insulation material and ambient temperature and are specified in standards.
Five safety rules for electrical systems and equipment
While the "small" causes mentioned in the last section can lead to significant damage, the good news is that cable fires can also be prevented quite easily by being attentive to your surroundings. Whether in a residential or commercial setting, if you follow these five rules, many hazards can be averted:
- Watch out for damaged insulation
Kinking or crushing cables can damage the insulation. In the same way, environmental influences such as gases or vapors can also attack the protective jacket. A crushed electrical conductor has a higher resistance: the cable can heat up dangerously at this point and breaks in the insulation can then cause leakage currents and short-circuits. If you accidentally discover damaged or defective wiring, you must immediately report it to a safety or electrical professional or. in the private sector, remove affected devices from service. The responsible specialist must immediately take damaged lines on electrical installations out of operation (de-energize or, if necessary, attach warning signs!) until the damage is properly repaired.
- Avoid overloads
As mentioned above, overloading a conductor can also lead to excessive heating. For example, when too many devices with too high a rating are connected to a single socket outlet. Very risky are additional, not firmly installed multiple sockets, on which then often too many consumers are connected. Care should also be taken with power guzzlers such as z. B. Electric heaters required. With lamps and lights pay attention to the indicated nominal power. With a maximum of 60 watts you must never use a 100 watt bulb!
- Make sure that defective contacts are repaired
Causes for contact problems can be, among other things, defective sockets, plugs or switches with a loose contact, but also contamination. A loose contact in a socket can cause an electric arc with a very high temperature and set fire to a wall made of particle board. This means: Anyone who notices apparently faulty contacts should immediately inform the responsible electrician. The damaged plugs or switches must be taken out of service until they have been repaired in order to avoid cable fires.
- Do not bypass fuses
Fuses have the function to interrupt the circuit in case of damage and thus prevent excessive heating of the conductor. It only works when it works. They must therefore never be "patched" or bridged. If, after a fire, it turns out that a tampered fuse was the cause, the insurance company will always refuse to pay compensation in the event of a cable fire! In addition, the person responsible could be charged with negligent arson. Again, similar to the above: If the fuse blows when you switch on an appliance: inform a qualified electrician and do not use the appliance until the damage has been repaired.
- Electrical operational tests
Always have the prescribed tests for electrical equipment carried out in good time.
Hazards at the point of operation in case of fire
If a fire should nevertheless occur in an electrical appliance or even in a plant, it is essential to observe the following three safety measures:
- Disconnect the affected device from the mains by unscrewing the circuit fuse or the main fuse. If this is not possible or the fuses are not in the immediate vicinity, unplug the device from the power outlet. It is best to use insulated pliers for this purpose.
- Start extinguishing work after disconnecting from the mains supply. Again, it is best to use a fire blanket or a powder extinguisher. CO 2 extinguishers.
- Do not use water to extinguish the fire – in the affected device can (e.B. In a television set) by capacitors still a dangerous high voltage be present. You risk an electric shock!
Preventive diagnosis of a developing cable fire by thermography tests
Thermographic inspections are an elegant way of detecting damage, especially to electrical systems. Thermography is an imaging, objective measuring method to determine surface temperatures without contact. Electrical systems can be inspected for weak points in a very short time and during operation.
Thermography is becoming more and more widely used in industry and commerce for the analysis of electrical systems. The fire hazard is only one topic among others. Maintenance is almost even more important in order to prevent production losses. Electrothermography is also becoming increasingly important for product development and quality assurance. Many electrical systems are becoming more and more compact and externally sealed, so that their cooling can become problematic. Thermography also helps here.
Contact us! We are happy to carry out thermographic inspections of equipment, wiring, fuses or control cabinets in accordance with DIN 54191 and VdS 2860 for you.
DPS – The testing company – We take care of your safety!
You can also find more information on how to test electrical systems and equipment legally, efficiently and with added value in accordance with DGUV 3 in our wiki on DGUV Regulation 3