Internal arc-faults are explosive electrical events that can cause serious harm. Consequences can include severe injuries to those located nearby and damage to equipment resulting in long – and costly - power outages. Finding ways to mitigate arc faults are essential in electrical installations.

The effects of an arc fault can be reduced significantly with the application of arc fault mitigations systems. When the arc fault is detected, the detection device sends a signal to the arc-fault reduction device, e.g. a circuit breaker or a quencher, which can then mitigate the harmful effect of the arc-fault. To ensure the performance of these detection devices, the IEC has published a new standard, IEC 60947-9-2 ED1, Low-voltage switchgear and controlgear - Part 9-2: Active arc-fault mitigation systems - Optical-based internal arc-detection and mitigation devices.

This new standard provides methods to characterize the performance of electrical relays used to detect the light produced by the arc-fault. According to François Cazals, Convenor of the working group responsible for the development of this standard (IEC SC 121A WG 19), “Because of the risks associated with arc-faults, there is a growing need for arc-fault sensing and mitigation devices. IEC 60947-9-2 offers the performance assurances for such devices and help ensure the safety of low-voltage installations.”

IEC 60947-9-2 addresses internal arc-fault control devices (stand-alone, multifunction or combined) as well as sensors used either to detect the optical effect of the arc-fault and that operate a mitigation device to minimize the effects of the arc-fault. Construction and performance requirements for these devices and sensors are defined as well as their electromagnetic compatibility. To ensure compliance with these requirements, a variety of different testing methods and their reporting are defined.

As Cazals notes, “With IEC 60947-9-2, we are enhancing the protection of people, power switchgear and control gear assemblies against the effects of internal arc-faults.”