Numerical generator protection REG316*4
1MRK502004-Ben
Page 20
Technical Data Func-
tions (cont’d)
Technical Data Func-
tions (cont’d)
ABB Switzerland Ltd
Utility Automation
Table 25: Underimpedance (21)
Table 26: Minimum reactance (40)
Features:
· Detection of two- and three-phase short circuits (back-up protection)
· Single- or three-phase measurement
· Circular characteristic centered at origin of R-X diagram
· Lowest phase value evaluation for three-phase measurement
Fig. 6 Underimpedance protection function
characteristics
Settings:
Impedance 0.025 to 2.5 U
N
/l
N
in steps of 0.001 U
N
/l
N
Delay 0.2 to 60 s in steps of 0.01 s
Reset ratio <106%
Starting time <50 ms (at f
N
)
Accuracy of pick-up values ±5%
Features:
· Detection of loss-of-excitation failure of synchronous machines
· Single- or three-phase measurement
· Out-of-step detection with additional time delay or count logic
· Circular characteristic
·
Tripping possible inside or outside the circle
Fig. 7 Minimum reactance protection function characteristics
Settings:
Reactance X
A
-5 to 0 U
N
/l
N
in steps of 0.01 U
N
/l
N
Reactance X
B
-2.5 to +2.5 U
N
/l
N
in steps of 0.01 U
N
/l
N
Delay 0.2 to 60 s in steps of 0.01 s
Angle a -180° to +180° in steps of 5°
Accuracy of pick-up values ±5% of highest absolute value of X
A
, X
B
(at f
N
)
Reset ratio (related to origin of circle),
105% for min. function, 95% for max. function.
Starting time <50 ms
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