ABB REG316 4 Series Operating Instructions Manual page 648

ABB Switzerland Ltd
Utility Automation
Technical Data Func-
Technical Data Func-
tions (cont'd)
tions (cont'd)
Numerical generator protection
Table 25: Underimpedance (21)
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
Delay
Reset ratio
Starting time
Accuracy of pick-up values
Table 26: Minimum reactance (40)
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
Reactance X
B
Delay
Angle a
Accuracy of pick-up values
Reset ratio
Starting time
0.025 to 2.5 U /l in steps of 0.001 U
N N
0.2 to 60 s in steps of 0.01 s
<106%
<50 ms (at f )
N
±5%
-5 to 0 U /l in steps of 0.01 U
N N
-2.5 to +2.5 U /l in steps of 0.01 U
N N
0.2 to 60 s in steps of 0.01 s
-180° to +180° in steps of 5°
±5% of highest absolute value of X
(related to origin of circle),
105% for min. function, 95% for max. function.
<50 ms
REG316*4
1MRK502004-Ben
Page 20
/l
N N
/l
N N
/l
N N
, X (at f )
A B N