So that leads to another question:
From the Sensata's PVAF-T data sheet. It doesn't tell the difference, the rest of the system would have to handle figuring out which it is.
As described in UL1699B Edition 2 (2013), there are two types of UL
1699B recognition: Type 1 and Type 2. UL 1699B Type 1 recognition
requires that the arc fault detector (AFD) detect a class of series faults.
It also allows that the AFD may detect a class of parallel faults. UL
1699B Type 2 recognition requires detection of both a class of series
and a class of parallel faults. Neither Type 1 nor Type 2 recognized AFD’s
are required to distinguish between parallel or series faults. UL 1699B
only requires that the AFD detect an arc of 300 W or more in conditions
defined in the standard.
Sensata’s PVAF-T AFD has UL 1699B Type 1 recognition only. As such,
it detects a class of series faults. The PVAF-T also detects a class of
parallel faults, but it does not distinguish whether a specific fault is
a series or parallel fault. System designers using the PVAF-T should
incorporate appropriate system responses for both series and parallel
faults in their designs. System designers should also read the UL 1699B
standard to fully understand the differences and capabilities of Type
1 and Type 2 AFD’s before designing an arc fault interruption system
including any UL 1699B recognized AFD.