ABB RELION REX640, Техническое руководство, Страница: 566 / 1960

In compensated networks, where distributed compensation coils are
also used to compensate earth-fault current, setting
Operating quantity
should be set to "Resistive". This enables secure and dependable
directional determination also in case of local overcompensation where
the earth-fault current produced by the healthy feeder can become
inductive.
When
Operating quantity is set to "Amplitude", the set minimum operate current
threshold (setting
Min operate current) is compared to the amplitude of
I
o stab
1
in
the whole defined operate sector (see
Figure 325
). This selection can be used in
unearthed networks.
+90 deg.
-90 deg.
+45 deg.
Tilt angle




0 deg.
Figure 325: 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
[ ]
< ⋅
(Equation 99)
[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 in order of 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
Protection functions 1MRS759142 F
566 REX640
Technical Manual