ABB RELION 620 Series Technical Manual page 173

1MAC504801-IB E
620 series ANSI
Technical Manual
time or if the fault current disappears while the fictive voltage is in use. When the voltage
is below Min trip voltage and hysteresis and the fictive voltage is unusable, the fault
direction cannot be determined. The fictive voltage can be unusable for two reasons:
• The fictive voltage is discarded after Voltage Mem time
• The phase angle cannot be reliably measured before the fault situation.
67/51P and 67/50P can be forced to the non-directional operation with the NON_DIR
input. When the NON_DIR input is active, 67/51P and 67/50P operate as a non-directional
overcurrent protection, regardless of the Directional mode setting.
Operating
quantity
Memory function
operate zone
Min trip
current
GUID-C30CD1A2-93E2-4A92-9FF3-58B7B2A98458 V1 EN
Figure 72: Operating zones at minimum magnitude levels
Level detector
The measured phase currents are compared phasewise to the set Pickup value. If the
measured value exceeds the set Pickup value, the level detector reports the exceeding of
Operating zone
Non-operating zone
Min trip
voltage
Section 4
Protection functions
Polarizing
quantity
167