ABB Relion 670 Series Applications Manual page 147

1MRK 511 401-UEN Rev. K
~
IEC09000022 V1 EN-US
Figure 65: Through fault current from A to B: I
~
IEC09000023 V1 EN-US
Figure 66: Through fault current from B to A: I
The function shall not operate for any of the calculated currents to the protection. The
minimum theoretical current setting (Imin) will be:

Im in MAX I
EQUATION284 V2 EN-US
A safety margin of 5% for the maximum static inaccuracy and a safety margin of 5% for
maximum possible transient overreach have to be introduced. An additional 20% is suggested
due to inaccuracy of instrument transformers under transient conditions and inaccuracy in the
system data.
The minimum primary current setting (Is) is:
I = 1.3 × I
s
EQUATION285 V3 EN-US
In case of parallel lines with zero sequence mutual coupling a fault on the parallel line, as
shown in Figure 67, should be calculated.
Bay control REC670
Application manual
I
fB
A
Z Z
A L
IED
I
fA
A
Z Z
A L
IED
Fault
 
, I
f A fB
min
© Copyright 2017 Hitachi Power Grids. All rights reserved
B
Z
~
B
Fault
IEC09000022-1-en.vsd
fB
B
Z
B ~
IEC09000023-1-en.vsd
fA
Section 8
Current protection
(Equation 36)
(Equation 37)
141