ABB REL 501-C1 2.5 Technical Reference Manual page 90

78
General fault criteria (GFC)
Figure 31: Operating characteristics of the GFC (impedance measuring principle) and zone
measuring elements
Figure 31 presents principally a shaped operate characteristic for an impedance based GFC func-
tion. Different designations have the following meaning:
• XFW: reactive reach in forward direction
• XRV: reactive reach in reverse direction
• RF: resistive reach within the unlimited area
• RLoad: resistive reach restricted by the minimum load impedance
• LA: expected load impedance angle
jX
XFW
ZONE 3
ZONE 2
ZONE 1
LA
XRV
ZONE 4
Chapter 4
Line distance
R
RLoad RF
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