However, electricity is one of the most common causes of fires and heat burns in homes and workplaces.
At the following link you can read the rules of electrical installations:http://electricalnews.gr/texnika-arthra/ilektrikes-egkatastaseis/nomothesia/item/398-kanones-ilektrikon-egkatastaseon
And the following basic rules of protection against fire and electric shock: http://electricalnews.gr/texnika-arthra/ilektrikes-egkatastaseis/nomothesia/item/368-basikoi-kanones-prostasias-apo-ton-kinduno-ilektropliksias-kai-fotias
Ignition in electrical installation
Ignition requires heat and fuel. All materials used in electrical equipment are designed to be non-flammable, not to be the necessary fuel for causing a fire.
In most cases, the fuel comes from materials located near electrical installations, while electricity provides only the right heat to ignite. This heat comes from the flow of electricity through the pipes. For this reason, international electrical installation regulations provide rules for the proper design of electrical installations.
Causes of Overheating
Poor connections: All electrical connections in an installation are strained either by vibrations, by high temperatures developed by the passage of current, or by environmental elements that erode the quality of metals.
All the above reasons increase the resistance of the connection to the passing current, as a result of which they significantly raise the temperature in the specific points.
For example, if in an electrical connection we have a current of 60Amp, with an initial resistance of 0.1 Ohm, then 360 watts of energy are produced locally . As long as the connection remains unmaintained, its resistance increases, resulting in a corresponding increase in power output.
Another dangerous symptom of poor connections is the formation of small electric arcs.
Electric arcs are small discharges (or discharges), which occur in cases where a bad connection opens and closes many times, resulting in small gaps in the opening and the creation of electric arcs. In these cases, the heat generated can cause problems with insulation or even cause fire if it is close to fuel.
Circuit overload: When a load draws a lot of current for its operation, then the appropriate selection of the corresponding circuit needs to be made, in order to transfer this current without creating overheating.
The overload of a circuit can be constant, in cases where extensions have been made without a corresponding improvement of the electrical installation, or momentarily due to the sudden demand for more current. In any case, overloading a circuit causes the conductors and components to overheat.
Wiring errors: Many times the electrical installation is a dynamic entity, which changes according to the needs and requirements of its users. For this reason, mistakes can be made that will cause serious damage or even fire. For example, a serious risk of failure can occur when switching a 20 Amp fuse to a 30 Amp fuse, allowing more current to flow through a smaller conductor. Respectively severe overheating can occur when we place a smaller conductor in a line with a high transit current.
Insulation error: Insulating materials have improved significantly in recent years compared to the past. Nevertheless, insulation continues to suffer significant corrosion from stresses such as aging, high temperatures and environmental pollution. The most well-known insulation fault is the short circuit. Short circuit is the phenomenon in which 2 conductors without insulation come in contact and remain stuck.
In this case, the protections should work to isolate the error area. If for any reason the fuses do not work, the whole circuit from the fault onwards, will receive large amounts of heat generated. In addition, when 2 pipes come close, they also produce discharges (arcs), which we mentioned above.
Finally, insulations that receive high temperatures from nearby sources are likely to corrode and become conductive, resulting in discharges, which are called arc tracking and have the same dangerous effects as electric arcs.
Lightning: A key function of grounding is to provide a path of very low ground resistance. Thus a lightning strike, which will hit a building will be directed to the ground without causing damage to other parts of the building, such as the electrical installation, where it could cause from severe overheating to fires. For this reason it is necessary to periodically check and measure the ground to ensure its proper operation when needed.
Harmonic: Harmonic distortions are derivatives of current, which have a different frequency than 50Hz. Harmonics produce non-linear loads such as motors, computers, etc.
Large deformations from harmonics, cause overheating in transformer windings and conductors. Especially 3 the harmonic produced by single-phase loads in three phasic systems may overheat hazardous neutral conductor.
Ways to control and deal with overheating and damage
The secret to early detection of faults in an electrical installation is to create a test file, recording important points and reference values. In this way, by generating reference values and making annual checks, we can easily detect changes in the good working condition of the equipment and prevent failures, the repair of which will be quite expensive or which could cause a fire in our electrical installation.
For the prognostic maintenance and timely diagnosis of faults in an electrical installation we have the following tools:
Visual inspection: It is very important to have a visual inspection of the equipment periodically. The reason is that while the current is invisible, the signs of stress are visible eg corrosion, discoloration, etc., while we can still have other signs, such as strange smells from materials that overheat.
Thermographic control: With thermography by an experienced inspector, we can detect in time and with great accuracy all overheating in an electrical installation. By implementing a periodic temperature control program, we can very successfully prevent damage due to overheating. Great care must be taken to observe all safety rules and the inspector to be properly trained to avoid unnecessary corrective actions from misdiagnosis.
Ultrasound Testing: In combination with Thermography, another basic Non-Destructive Testing is the ultrasound inspection. With ultrasound we can detect early discharges and arcing, tracking and Corona phenomena, in the early stages before they even cause severe overheating with unpredictable consequences.
Energy Quality Analysis: For cases of failures due to transients, harmonics, overvoltages and other causes arising from the quality of energy supplied, a record can be made for a period of time in the quality of energy with a suitable analyzer, from which data for improvement actions will emerge.
Maintaining an electrical installation in perfect working order, without unexpected failures and risks, is a dynamic task, which needs good organization and the right tools. Proper technical training and appropriate equipment combined with experience can ensure the smooth operation of an electrical installation
source: infraspec.gr
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