Four Step Residual Overcurrent Protection - ABB Relion 670 Series Applications Manual

Section 7
Current protection
~
ANSI09000025 V2 EN-US
Figure 62: Two parallel lines. Influence from parallel line to the through fault current: I
The minimum theoretical current setting (Imin) will in this case be:
³
I m in M A X I
EQUATION287 V1 EN-US
Where:
I and I
fA fB
Considering the safety margins mentioned previously, the minimum setting (Is) is:
I = 1.3 × I
s
EQUATION288 V3 EN-US
Transformer inrush current shall be considered.
The setting of the protection is set as a percentage of the base current (
Operation : set the protection to Enabled or Disabled .
Pickup : Set operate current in % of IBase .
MultPU : The operate current can be changed by activation of the binary input MULTPU to the set
factor MultPU .
7.4 Four step residual overcurrent protection, (Zero
sequence or negative sequence directionality) EF4PTOC
(51N/67N)
136
A C
Z
A
Fault
I
M
IED
, ,
( I I )
fA fB M
have been described for the single line case.
min
Line 1
B
Z
L1
Z
B
M
Z
L2
Line 2
1MRK 511 358-UUS A
~
ANSI09000025_2_en.vsd
IBase ).
Application manual
M
(Equation 36)
(Equation 37)
IP14509-1 v6