ABB REG670 Applications Manual page 329

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
A
Z
~
A
IEC09000025 V1 EN
Figure 171: Two parallel lines. Influence from parallel line to the through fault
current: I
The minimum theoretical current setting for the overcurrent protection function
(Imin) will be:
³ , ,
Imin MAX I ( I I )
fA fB M
EQUATION82 V1 EN
Where I and I have been described in the previous paragraph. Considering the
fA fB
safety margins mentioned previously, the minimum setting (Is) for the instantaneous
phase overcurrent protection 3-phase output is then:
Is ³1.3·Imin
EQUATION83 V2 EN
The protection function can be used for the specific application only if this setting
value is equal or less than the maximum phase fault current that the IED has to clear.
The IED setting value IP>> is given in percentage of the primary base current value,
IBase. The value for IP>> is given from this formula:
Is
>>= ×
IP 100
IBase
EQUATION1147 V3 EN
Line 1
C
Z
L1
M
Fault
Z
L2
I
M
Line 2
IED
M
Section 9
Current protection
B
Z
~
B
IEC09000025-1-en.vsd
(Equation 178)
(Equation 179)
(Equation 180)
323