Arc flash

An arc fault or fault arc is in the electric power industry an unwanted arc occurring between electrical parts of the system.

Flashover

With insufficient distance or inadequate insulation between two electrical potentials can cause an unwanted voltage flashover, during which an electric arc is created. This voltage flashover can occur in an electrical component itself, because the contacts to slowly separate, or the insulation layer between the live parts of their insulation was robbed.

The arcs that arise in flashover, usually put the life of the component massively reduced and can also destroy it in the worst case.

Arcs are a significant risk in high- voltage power lines. Especially on overhead lines of electric railways, it always comes back to serious accidents when people approach the lines too much.

In the low voltage range arcing faults can occur as a result of defects in electrical wiring, usually in the following line damage:

• Damaged insulation due to line bruising, damage caused by nails or screws or small bending radii for electrical wires. This leakage can be caused by dirt and debris that ignite in an arc
• Lose contacts when not properly mounted components, by rodent attack and erosion or kinked lines. This is where arc faults by ionized gases between the loose cable ends

On printed circuit boards, especially common in switching power supplies, direct rollovers to significant damage because the conductor material (copper) deposited on the circuit board material as the metal vapor layer and bridges creepage distances. If no replacement of the entire assembly is possible, such damage is restored through slots in the board; the new leakage path consists of an air gap. As a precautionary measure used pads with hollow rivet, thicker copper layers with wire reinforced ladder trains, chambered enclosure and generously dimensioned creepage distances. Is at odds with the miniaturization.

Occupational Safety and Health

Due to the low loop impedances in the range of some 10 milliohms in electrical power systems, such as the main distribution of low voltage networks, can lead to short circuits or installation error very high short -circuit currents up to several 10 kA. The resulting arc leads, due to the high instantaneous power, a sudden evaporation of metallic contact material, which can lead to thermal damage such as burns in the area.

For this reason, appropriate fire resistant protective clothing when working in the potential area of ​​influence of an electric arc to carry with face shield and visor and use the appropriate tools. The risk areas include, inter alia, in the main junction exchange of NH- fuse links under tension or non-electrical maintenance in operated high-voltage switchgear.

Plant protection

In the low voltage range arcing faults can lead to fire damage. Different fuses bow before such damage:

• Correctly designed circuit breaker, English Circuit Breaker or fuse can selectively disable short-circuit currents and prevent further damage to the system.
• Fault arc protection devices english Arc -Fault Detection Devices, AFDD can detect short arcing faults in the low voltage range and interrupt the flow of current. Commercially there is also the name of fire protection switch