What can cause a phase reversal fault in an S811+?

There can be several reasons an S811+ unit can fault trip on a phase reversal fault without having a true phase reversal condition.

One reason is phase loss. With only 2 phases being detected by the unit, the unit cannot determine phase rotation. This type of fault may be combine with a phase loss fault trip.

Another reason may be that the frequency parameter is not configured properly. The default value is 50 Hz. If the unit is operating with a system frequency of 50 Hz, this fault trip may occur. The tripping action may be corrected by changing the Rated Line Freq (Frequency) parameter located in the Protections Menu to the correct value.

In the event of using a generator, the frequency of the generator may be drifting enough to cause the unit to fault trip. If the generator frequency cannot be stabilized, the Rated Line Freq parameter can be changed to Warning or Disable.