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

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Abschnitt 4.1 , 4 Instructions for practical application wit...
Abschnitt 4.1
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 4.1 – 4 Instructions for practical application with practical examples
4.1 Instructions for practical application

A worksheet (Excel) has been developed to support use of the methodology, which can be downloaded from the Internet at the BG ETEM homepage (www.dguv.de; Webcode: d138299).

The following basic conditions should be considered when implementing the evaluation process in practice:

  • The requirements set forth in BGV/GUV-V A3 "Electrical Systems and Equipment" should be taken into account, particularly with respect to the use of additional PPE for work on live equipment or in the vicinity of live system components.

  • The methodology only covers that protection afforded against the thermal effects of an electric fault arc. Experience has shown these effects have the most severe consequences. Electric fault arcs in high-energy systems can lead to further hazards caused by shockwaves, noise, optical radiation or escaping electric arc gases.

  • If use of the selection algorithm determines that the protective properties of the PPE selected for the work process being considered are not adequate, the following exemplary measures could be considered in more detail:

    • The protection device's characteristics and corresponding trip time have a significant influence on the potential electric arc energy in the event of a fault. Replacement of the upstream protection device with a fast-acting industrial protection device or adjustment of the circuit breaker tripping characteristics during the work period might be considered in this context 3) .

    • A separate protection device for electric fault arcs detects the electric arc by means of a sensor system, immediately initiates a bolted short-circuit and triggers the upstream protection device. The duration of arc combustion is reduced in this manner to just a few milliseconds.

      These devices can be foreseen for permanent installation during the system planning stage or can be used for mobile applications 4) .

    • If the working distance can be increased, this will greatly influence the equivalent arc energy. Thus, it may well make sense to consider whether an increase in the working distance could be realised with the aid of additional auxiliary devices.

    • Short-circuit power at the workplace can be reduced by means of a modified circuit variant depending on the system configuration (e. g. disconnection of a machine network connection, removal of a parallel connection). Subsequent to these measures, the calculation process should be applied again for the modified network parameters.

  • If the maximum value k Pmax was used to determine normalised arc power k P in the initial analysis, the calculation will be on the safe side, but it may also result in exceeding the target in practice. In this case, it is worthwhile calculating using a typical reference value or with consideration given to the practical system configuration.

  • The geometry of the real system is entered into the calculation. The transmission factor k T, which is normally established at the start during the initial approximation, can then be adapted based on the actual geometric system conditions and the working environment. If a deviation from transmission factor k T = 1 is intended, this determination must be justified.


    If evaluation shows that the protective properties of the clothing made available are inadequate for the work process being considered and measures such as increasing the working distance, reducing the electric arc energy or introducing additional electric fault arc-resistant partition walls, can not be taken, then work must not be performed if the system has not been electrically isolated.

    NOTE:
    If observation reveals potential hazards associated with system operation, such as during system isolation, against which the available PPE does not offer adequate protection, then special consideration should be made in each individual case. Measures such as isolating the upstream network may be conceivable in this context.

  • The manufacturer's instructions must be observed to ensure the PPE provides the appropriate protection in the event of a fault. In particular, it is essential to adhere to the instructions for proper usage, as well as those specified by the manufacturer for proper care. At the same time, it is recommended to wear cotton underwear.

3)

Strasse, U., Erfahrungen beim Einsatz von Arbeitssicherungen beim AuS im Kabelnetz von Vattenfall Europe Berlin; ETG Fachbericht Fachbereich 106 Arbeiten unter Spannung (AuS), Presentation for the ETG-Technical Meeting in Dresden from 19. to 20. September 2007.

4)

Rotter, G., Bähnsch, R., Lichtbogenschutz-System DEHNarc - Geräte-System und Anwendung in der Praxis, 15 th BG ETEM Electrical Engineering Technical Meeting in Kassel, 2010.