ABB RELION REX640 Technical Manual page 543

1MRS759142 C
REX640
Technical Manual
+90 deg.

Tilt angle
-90 deg.
GUID-68F17A2E-924C-4260-910A-AF9EED1AD3FB V1 EN
Figure 292: Operating quantity = "Amplitude" and Directional mode = "Forward"
If the "Adaptive" or "Resistive" operating quantity is selected, the setting Min operate
current should be set to value:
pu p IRtot
  < ⋅
 
GUID-F502A858-0BE7-4F16-A032-3B01D2D90574 V1 EN
[pu] Min operate current
IRtot 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 1...5 % of the total
capacitive earth-fault current of the network)
p security factor = 0.5...0.7
It must be set to a value which is lower than the total resistive earth-fault current in
order to enable dependable operation.
Estimation of the total resistive earth-fault current of the network including the
parallel resistor of the coil and the network losses can be obtained from the network
calculation results of the coil controller in resonant earthed networks. In Petersen coil
controller, this value is denoted as 'I_DAMPING' [A]. When evaluating this
numerical value, the connection status of the parallel resistor of the coil must be
considered. See the example in
has value 8.6 A and it is permanently connected. The total system damping is
calculated as 11.29 A. Thus the natural network losses including the losses of the coil
are 11.29 A - 8.6 A = 2.69 A.
+45 deg.

0 deg.


Figure 293. In this case, the parallel resistor of the coil
Section 4
Protection functions
(Equation 87)
537