ABB REG316 4 Series - Page 645

Numerical generator protection
ABB Switzerland Ltd
Utility Automation
REG316*4
1MRK502004-Ben
Page 17
Table 17: Generator differential (87G)
Table 18: Transformer differential (87T)
Features:
· Three-phase function
· Current-adaptive characteristic
· High stability for external faults and current transformer saturation
Settings:
g-setting (basic sensitivity) 0.1 to 0.5 I
N
in steps of 0.05 I
N
v-setting (slope) 0.25 or 0.5
Max. trip time
- for I
D
>2 I
N
- for I
D
£2 I
N
£30 ms
£50 ms
Accuracy of pick-up value of g ±5% I
N
(at f
N
)
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 0.1 to 0.5 I
N
in steps of 0.1 I
N
v-setting 0.25 or 0.5
b-setting 1.25 to 5 in steps of 0.25 I
N
Max. trip time (protected transformer loaded)
- for I
D
> 2 I
N
- for I
D
£ 2 I
N
£30 ms
£50 ms
Accuracy of pick-up value ±5% I
N
(at f
N
)
Reset conditions I
D
<0.8 g-setting
Differential protection definitions:
ID = êI
1
+ I
2
+ I
3
ê
0
a = arg (I
1
' - I
2
')
2-winding: I
1
' = I
1
, I
2
' = I
2
3-winding: I
1
' = MAX (I
1
, Ì
2
, Ì
3
)
I
2
' = I
1
+ I
2
+ I
3
- I
1
'
Fig. 5 Differential protection characteristic
I
H
I
1
¢ I
2
¢acos××=
for cos a ³0
for cos a
<0