ABB REG316 4 Series Operating Instructions Manual page 645

ABB Switzerland Ltd
Utility Automation
Numerical generator protection
Table 17: Generator differential (87G)
Features:
· Three-phase function
· Current-adaptive characteristic
· High stability for external faults and current transformer saturation
Settings:
g-setting (basic sensitivity)
v-setting (slope)
Max. trip time
- for I >2 I
D
N
£2 I
- for I
D
N
Accuracy of pick-up value of g
Table 18: Transformer differential (87T)
Features:
· For two- and three-winding transformers
· Three-phase function
· Current-adaptive characteristic
· High stability for external faults and current transformer saturation
· No auxiliary transformers necessary because of vector group and CT ratio compensation
· Inrush restraint using 2nd harmonic
Settings:
g-setting
v-setting
b-setting
Max. trip time (protected transformer loaded)
- for I > 2 I
D
N
- for I £ 2 I
D N
Accuracy of pick-up value
Reset conditions
Differential protection definitions:
I D
= êI ê
+ I + I
1 2 3
¢ I × ¢ × a
I = I cos
H 1 2
0
a = arg (I
' - I ')
1 2
2-winding :
I ' = I , I ' = I
1 1 2
3-winding :
I ' = MAX (I
1
I ' = I + I
2 1 2
0.1 to 0.5 I
0.25 or 0.5
£30 ms
£50 ms
±5% I (at f
N
0.1 to 0.5 I
0.25 or 0.5
1.25 to 5 in steps of 0.25 I
£30 ms
£50 ms
±5% I (at f
N
I <0.8 g-setting
D
for cos a ³0
<
for cos a 0
2
, Ì , Ì )
Fig. 5 Differential protection characteristic
1 2 3
+ I - I '
3 1
1MRK502004-Ben
in steps of 0.05 I
N N
)
N
in steps of 0.1 I
N N
N
)
N
REG316*4
Page 17