DGUV Information 203-078 - Thermal hazards from electric fault arc Guide to the ...

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Abschnitt 3.4 , 3.4 Determination of equivalent arc energy
Abschnitt 3.4
Thermal hazards from electric fault arc Guide to the selection of personal protective equipment for electrical work (bisher: BGI/GUV-I 5188 E)
Titel: Thermal hazards from electric fault arc Guide to the selection of personal protective equipment for electrical work (bisher: BGI/GUV-I 5188 E)
Normgeber: Bund
Amtliche Abkürzung: DGUV Information 203-078
Gliederungs-Nr.: [keine Angabe]
Normtyp: Satzung

Abschnitt 3.4 – 3.4 Determination of equivalent arc energy

The equivalent arc energy is the protection level afforded by the PPE. It is determined by the test level for the PPE, working distance a and the equipment geometry (Factor k T).

Working distance a is the distance between the electric arc and the person's body (torso) that is effective during the work activity or must be maintained in the working environment being considered. Where different tasks are being carried out in the working environment, the shortest distance emerging should be applied. (see Annex A 3.3.5)

It can generally be assumed that the distance to the person's torso when working will not fall short of a = 300 mm and that, particularly in the low voltage range, this can be applied as a reference value.

The transmission factor k T takes into account the electrical system's geometric configuration and describes the spatial propagation of the electric arc thermal impact in space.

In a small-scale system, a directional propagation of the electric arc thermal impact occurs. The more open or large-scale the system, the more omnidirectional the electric arc thermal impact propagation will be.

Exemplary pictures of real system configurations are depicted in Section 4.3.

The test method used to verify the thermal impact of an electric fault arc is described in detail in Annex A 3.1.

The test method differentiates between two classes, which define the protective properties of the PPE against the thermal effects of an electric fault arc (test level). Both classes are verified through electric arcing with subsequent electric arc energies, as well as through the use of the test setups described in the test method.

Class 1 W LBP1 = 158 kJ
Class 2 W LBP2 = 318 kJ

Fig. 5
Determination of equivalent arc energy with consideration given to working distance and geometry


Box V = 1,6 l
Side and rear walls
low volume

Rear wall only or large combustion space volume

Electric arc burns openly (very large combustion space volume)
k T = 1,0 k T = 1,5 ...1,9 k T = 2,4

Fig. 6
Transmission factor reference values for different equipment relationships

An equivalent arc energy W LBä, at which level protection is still afforded by the PPE for the respective distance a, can be determined for any working distance a over the experimentally verified reverse squared distance proportionality, using the electric arc energy of the test category W LBP 2) . In addition, the system configuration can be taken into consideration using factor k T. Generally valid for the Box test

2)

Feasibility study related to the testing and evaluation of protective gloves against the thermal hazards of electric fault arcing (AG: BGFE; AN: STFI/TU Ilmenau), STFI final report from 30 May 2005.