The device from the 5SM6 product family detects hazardous arcing faults in the strings of a PV system, and responds with an immediate acoustic and visual alarm.
Arcing faults occur in defective string insulation or faulty cables. The result is rapid overheating, which may cause smouldering fires. The AFDD can be combined with other protection and switching devices, eg a moulded case circuit breaker (MCCB).
The device combination will ensure an automatic disconnection of the relevant system part in case of an arcing fault. Siemens has previously been offering AFDDs for electric installations in buildings.
In order to prevent smouldering fires in PV systems, an AFDD permanently measures the intensity and duration of high-frequency noise associated with the voltage and current, as well as noise lapses. Any abnormalities are reported immediately.
Once the cause for an arcing fault has been remedied, the AFDD can then be reset. The arcing fault LED will light up again immediately if the problem was not completely resolved or if other arcing faults are occurring. AFDDs can be surface-mounted or clipped onto a standard mounting rail. The device is therefore easily integrated in new systems and can be retrofitted in existing systems.
Arcing faults are a particularly high risk in solar power systems: On the one hand, the installations are often subject to extreme environmental conditions, including pressure from snow loads or high winds, which can result in damage to the system. On the other hand, a solar system represents an increased risk for rescue workers in case of fire when attempting to extinguish the fire with water, if no appropriate disconnecting device is installed with the result that the systems are still supplied with voltage.