ABB Relion 670 Series Applications Manual page 139

1MRK 511 401-UUS F
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ANSI09000025 V2 EN-US
Figure 59: 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
EQUATION82 V1 EN-US
Where I
fA
mentioned previously, the minimum setting (Is) for the instantaneous phase overcurrent
protection 3-phase output is then:
Is ³1.3·Imin
EQUATION83 V2 EN-US
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
value for
=
Pickup
ANSIEQUATION1147 V1 EN-US
8.2 Directional phase overcurrent protection, four steps
OC4PTOC(51_67)
Bay control REC670
Application manual
A C
Z
A
Fault
I
IED
, ,
( I I )
fA fB M
and I have been described in the previous paragraph. Considering the safety margins
fB
Pickup is given in percentage of the primary base current value, IBase . The
Pickup is given from this formula:
Is
×
100
IBase
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Line 1
B
Z
L1
Z
B
M
Z
L2
M
Line 2
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ANSI09000025_2_en.vsd
Section 8
Current protection
M
(Equation 27)
(Equation 28)
(Equation 29)
SEMOD129998-1 v8
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