With regards to the ARC containment in low voltage assemblies, the testing under arcing conditions is considered to be a voluntary/special test and not a specified requirement of BS EN 61439 so not all IEC low voltage assemblies currently in use have under gone the tests. The testing/level of protection is generally at the manufacturer’s discretion or an agreement with the manufacturer and the end user. The test standard is IEC/TR 61641.
The purpose of these tests is to assess the low voltage assembly’s ability to limit the risk of injury and damage which result from an internal arcing fault.
Assessment criteria for personnel protection (criteria 1-5):
1. Properly secured doors, covers, etc., must not open.
2. Parts (of the switchgear and controlgear assembly) must not pose a risk of injury or damage by becoming detached and / or projected as a result of the arc fault.
3. No holes must form in the freely accessible external parts of the enclosure due to burn-out or other effects as a result of arc exposure.
4. Vertically attached indicators must not ignite (indicators which are ignited by burning coats of paint or burning labels are to be excluded from this assessment).
5. The protective conductor circuit for touchable parts of the enclosure must remain functioning.
Assessment criteria for system protection (criteria 6-7):
6. The arc must be restricted to a defined zone and no re-ignition must take place in the adjoining zones.
Additional condition for emergency operation:
7. Emergency operation of the switchgear and control gear assembly must be possible after fault rectification or after disconnection or de-installation of the affected functional units. This has to be verified by means of an insulation test with 1.5 times the value of the rated operating voltage over 1 minute.
To meet the test requirements the protective measures are either active or passive protection as shown below;
Whilst the Siemens Sivacon S8 has been tested to meet the criteria of IEC/TR 61641 they have come up with a level concept for flexibility and cost-efficient solutions to the end users actual requirements.
