GE F650 Instruction Manual page 200

5 SETTINGS 5.4 PROTECTION ELEMENTS
The polarization diagram is as follows:
5
Figure 5–10: POLARIZATION DIAGRAM
The diagram shows a fault in phase A, therefore the Operation magnitude is IA, the polarization magnitude is VBC, which
has been rotated the torque angle set as MTA. Positive angles are considered as counter clockwise rotations, and negative
angles clockwise rotations. Direction is considered to be forward when the fault current is inside an arc of ±90º to both sides
of the polarization voltage. In the directional element settings there is a Direction setting that allows to select in which area
the element operation is allowed, either forward or reverse. Operation areas include a safety zone of 5º to each side of the
cone. This safety cone is applied when the operation direction calculation is performed from initial block conditions. When
we go from a non-trip area to a trip area, the safety cone is considered. In case we go from a trip area to a non-trip area,
this cone will not be considered, and the whole area will be operative. This safety cone is located always in the operation
area, both in forward and reverse cases.
NOTE: In situations where a current inversion is produced during a fault, the phase directional element will require a period
of time to establish the blocking signal. This time is approximately 20 ms. Certain instantaneous overcurrent elements can
be activated before receiving the blocking signal from the directional element. In cases where these situations can be
expected, we recommend to add a 50ms delay to IOC elements.
GEK-106310AB F650 Digital Bay Controller 5-53