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May 31, 2017

What is IEC Box Arc Testing, and How Does it Compare to Open Air Arc Testing?

You may have heard of “box testing” or seen the standard designation for “IEC 61482-1-2”. What is this test, and how is it different from open-air arc testing and an ATPV or EBT arc rating?

Box testing, as performed by IEC 61482-1-2, does not produce an arc rating. Instead, 2 different “arc protection” classes are used in testing, and a material or garment will be assigned with a Class 1 or a Class 2 result if the test is passed. In box testing, no crossings of the Stoll Curve are permitted. For material testing, four specimens are tested; if only one of the four specimens indicates a crossing of the Stoll Curve, a fifth sample is permitted to be evaluated to determine compliance. If the fifth specimen indicates a crossing of the Stoll Curve, the specimen fails. The two exposure classes are as follows:

Class 1: 4kA, 0.5 s exposure

Class 2: 7 kA, 0.5 s exposure

The video above shows an arc-in-a-box test playing in slow motion. These exposures were based on German electric utility studies which focused only on a low voltage exposure. German standards are in the process of being developed to correlate the box method and are effective at the two levels. The method is commonly used in the EU and is required by some notification bodies for CE Markings. The UK allows either box arc or open air arc testing for CE Markings, but some of the EU allows only box arc testing because of a belief that it alone meets the EU requirement to protect workers from all burns. This interpretation fails to understand arc testing and arc flash exposures. Arc Ratings and Protection Classes are both conservative for many reasons–the pros and cons of box testing are laid out below.

Pros:

  • LV exposure makes more labs available to perform the box test
  • AL and CU metal used are more common in actual arc exposures
  • 4 exposures means less fabric is used
  • Pass/Fail makes interpretation easier, no statistical analysis is required to determine classification levels

Cons:

  • No direct standard (like IEEE 1584 or NFPA 70E) to correlate Arc Protection Box Class to field hazards
  • Two levels means exposures higher than Class 2 cannot be evaluated (Class 1 is from 4-8 cal/cm² approximately and Class 2 is from 12-20 cal/cm² approximately)
  • Pass/Fail information only, not as useful as specific values assigned by the open-air test
  • The repeatability of fabrics on the edge is not as easy to identify

ArcWear is part of FlashCert and partner’s with Kinectrics to perform all arc testing standards. Additionally,  ArcWear is an ISO 17025 accredited lab for textile testing for flame and thermal including ASTM F1506, NFPA 70E, OSHA 1910.269, NFPA 2112 and many other specifications related to arc flash, flash fire, and fire fighting.

6 Comments on “What is IEC Box Arc Testing, and How Does it Compare to Open Air Arc Testing?

Markus Berger
June 1, 2017 at 8:54 am

Could the box test be done on gloves too or fabrics only?

Reply
Stacy Klausing
June 1, 2017 at 2:35 pm

Hi, Markus! At this time, the box method cannot be performed on gloves. The scope is limited to fabric and garments. Today, the only arc test method published for gloves is ASTM F2675. Work is being done on an IEC version and Hugh participates on the committee. Stay tuned, as we will certainly post relevant updates!

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Hugh Hoagland
June 8, 2017 at 2:53 pm

We can offer a version of the proposed standard as performed in Germany but this is not an IEC standard and the standard could change.

Reply
Jaap Hoogerduijn
June 9, 2017 at 3:19 am

And what about the safety aspect? Open Arc testing (ATPV or EBT) includes 50% burns..

Would be interesting to see further development of the ELIM testing. Cons of the open arc values and Cons of box test (less van 50% burns)

Reply
Jaap Hoogerduijn
June 9, 2017 at 3:39 am

Typo, open arc: 50% change on seconde degree burns

Reply
Zarheer Jooma
July 7, 2017 at 10:13 am

We have presented almost all of our data to the TC78 WG15 committee as part of the due diligence exercise. There was no improvement over either measure of arc rating.

The point made may be theoretically arguable, however, from our more than 150 investigations, either of the three expressions of arc rating would have sufficed in preserving life. Practically, arc impedance reduces the max theoretically calculated energy AND the methods used to quantify the available arc flash energy are conservative – arc rating (expressed in whichever measure) works.

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