ABB RELION 620 Series Technical Manual page 484

Section 4
Protection functions
478
GUID-0A818501-E0BD-402F-BF8B-22BA6B91BBA2 V1 EN
Figure 240: Illustration of amplitude and resistive current sectors if Operating
quantity is set "Adaptive" and Directional mode is set "Forward"
The setting rules for current thresholds are given below.
In case the "Adaptive" operating quantity is selected, the setting Min operate current
should be set to value:
pu p IRtot
[ ]
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IRtot The total resistive earth-fault current of the network corresponding to the resistive current of the
parallel resistor of the coil and the natural losses of the system (typically in order of 1...5 % of the
total capacitive earth-fault current of the network).
p security factor = 0.5...0.7
This setting should be set based on the total resistive earth-fault current of the network
including the parallel resistor of the coil and the network losses. It must be set to a
value which is lower than total resistive earth-fault current in order to enable
dependable operation.
1MRS757644 F
(Equation 56)
620 series
Technical Manual