a) Z locus in under excitation for heavily loaded machine
b) Z locus in under excitation for lightly loaded machine
c) Z locus for a fault in the network
X (Reactance)
R (Resistance)
-X
Relay operation
characteristics
-R
a
b
c
Figure 568: Typical impedance locus in underexcitation: a) heavy load b) light load c)
fault in the network
4.7.3.7 Signals
UEXPDIS Input signals
Table 949: UEXPDIS Input signals
Name Type Default Description
I3P SIGNAL - Three-phase currents
U3P SIGNAL - Three-phase voltages
BLOCK BOOLEAN 0=False Block signal for acti-
vating the blocking
mode
EXT_LOS_DET BOOLEAN 0=False External signal for
excitation loss detec-
tion
UEXPDIS Output signals
Table 950: UEXPDIS Output signals
Name
Type Description
OPERATE BOOLEAN Operate
START BOOLEAN Start
1MRS759142 F Protection functions
REX640
Technical Manual
1023
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