ABB RELION REX640 Technical Manual page 565

1MRS759142 F
When
threshold (setting Min operate current) is compared to the resistive component of
1
I
o stab
Figure 324: Operating quantity = "Resistive" and Directional mode = "Forward"
The resistive mode is valid for resonant earthed networks and high-resistance
earthed systems, but not in case of unearthed networks. The resistive mode must
be selected when there is a risk of local overcompensation of a protected feeder,
that is, when the earth-fault current is compensated with distributed compensation
coils and their inductive current exceeds the amount of capacitive current produced
by the phase-to-earth capacitances of the feeder.
REX640
Technical Manual
Operating quantity should be set to "Adaptive" in resonant
Setting
earthed systems, except when protected feeders are overcompensated
by distributed coils. In such a case,
"Resistive".
Operating quantity to "Adaptive" enables secure and dependable
Setting
directional determination in compensated networks, which is also valid
when the compensation coil is switched off and the network becomes
unearthed. In case of an unearthed network,
automatically compared to the amplitude of
earth-faults, harmonics created by the fault type make the accumulated
sum admittance phasor behave as in case of an unearthed network.
Therefore, operation can be achieved without the need for resistive part
1
I
of . This also means that in compensated networks during earth
o stab
faults with rich harmonic content in residual quantities, operation can
be achieved without the parallel resistor of the centralized compensation
coil.
Operating quantity is set to "Resistive", the set minimum operate current
in the whole defined operate sector (see
+90 deg.


Tilt angle
-90 deg.
Operating quantity should be set to
Figure 324
+45 deg.
0 deg.


Protection functions
Min operate current is
1
I
. In case of restriking
o stab
).
565