Figure 250: 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
[
]
<
⋅
(Equation 57)
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 H
Protection functions
620 series
Technical Manual
489
