Arc Flash Protection tests

Arc flash protection is a fairly familiar thing to electrical engineers worldwide. However, clearly less well-known is the Arc Flash protection with an Arc Quenching Device AQD.
This was one of the main reasons which led Arcteq to carry out arc protection primary tests at the IPH-accredited laboratory in Berlin in March 2022.

The aim of the tests was to conclude, that in addition to the normal equipment testing, the tests should concretely illustrate the consequences of an arc fault depending on the relay protection solution used in switchgear.

As a result of a more detailed design, it was decided to carry out the testing in such a way that results are obtained from at least three different arc flash situations:

  1. Switchgear without arc relay protection with a fault duration of approx. 300ms (e.g. overcurrent protection in some cases)
  2. Switchgear with arc relay protection, where the main circuit breaker is controlled open (fault duration approx. 68ms, consisting of arc relay protection delay + circuit breaker operational delay)
  3. Switchgear with arc protection and arc quenching device (fault duration approx. 3.2 – 4.4ms)

 

What is an arc quenching device?

Arc quenching device (AQD) is a device in which three phases are connected to the switchgear main busbar. When arc relay protection detects arc flash it sends an operating command to AQD. AQD creates an extremely fast, and extremely low-impedance three-phase alternative path, which absorbs the arc incident energy in full and resulting voltage of the busbar collapsing to zero, leading to arc fault being extinguished (if the voltage is zero or almost zero, the arc fault can’t continue burning)

In the following video, you’ll see very clearly what it means when;

  • the switchgear does not have arc protection (left),
  • the switchgear has traditional arc relay protection without an arc quenching device (middle)
  • the switchgear has arc protection with an arc quenching device (right)

(Video was taken with a 1000FPS high-speed camera and the moment of arc ignition is synchronized between videos with a resolution of 100μs)

As can be seen very well from the video, arc relay protection with an arc quenching device makes a significant difference in case of an arc fault.

2020 IEC TS 63107 standard was published concerning the integration of internal arc-fault mitigation systems in power switchgear and control gear assemblies according to IEC 61439-2.

Testing according to IEC TR 61641 was undertaken successfully. AQ-1000 also meets the highest level of IEC 60947-9-1 Arc Quenching Devices standard.

It can be said that integration standards and beyond regarding this subject were fulfilled.

 

Conclusion:

After performing the arc fault tests, we are certain that:

  • Arc protection with an arc quenching device significantly increases both personal and equipment safety.
  • Downtime in distribution systems is marginal compared to traditional protections.
  • Using AQD drastically reduces the arc flash incident energy level and consequently PPE requirement.
  • If you want to do everything you can to protect both, your staff and your equipment, your decision undoubtedly is re-usable AQD system

For cost savings, would you leave seat belts and airbags off the cars nowadays?

 

Mikko Manninen
Arcteq Relays Ltd
Product Manager Arc Products