5-64 F650 DIGITAL BAY CONTROLLER GEK-106310-AF
5.4 PROTECTION ELEMENTS CHAPTER 5: SETPOINTS
The polarization diagram is as follows:
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.When going from a trip area to a
non-trip area, this cone is not considered, and the whole area is operative. This safety cone is always located 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 requires 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.
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