Phase sequence error sensed on busbars


Please could someone explain what would cause a phase sequence error alarm on the bus bar side. And how is the DEIF controller sense this error(Using what measurement).

Kind regards

Valence... You must provide additional information?
1) What version of the DEIF is it?
2) What are the parameters of the Generator controlled by the DEIF.
3) Is this a commissioning situation or has the unit been in operation a while?
Regards, Phil Corso