ABB Relion 670 Series Technical Reference Manual page 173

1MRK505222-UUS C
Technical reference manual
Current variation
I3P
subfunction
i
ANSI10000295 V1 EN
Figure 67: Current variation logic diagram
Time Delay CV is the time setting for the change of current criterion. Phase current
samples are included in input signal I3P.
Zero sequence current criterion
Zero sequence criterion is mainly for detection of remote IED high resistance faults or
some gradual faults. The criterion takes the zero sequence current as input. Zero
sequence current is compared with PU 3I0 for the t3I0 time to generate the zero
sequence current startup signal.
I3P
PU 3I0
BLOCK
ANSI09000778 V2 EN
Figure 68: Zero sequence current criterion logic diagram
Here PU 3I0 is the setting of the maximum possible non-faulted zero sequence current
for the protected line. The default value for this setting is 0.1 · IBase where IBase is the
rated current of the CT.
t3I0 is the time setting for the zero sequence current criterion.
Time Delay CV
t
Time Delay CV
t
Time Delay CV
t
a
a>b
b
AND
OR
Section 5
Differential protection
Pick Up VAB
cont
Pick Up VBC
Pick Up VCA
STCV
OR
cont
ANSI10000295-1-en.vsd
t3I0
Pick Up 3I0
t
ANSI09000778-2-en.vsd
167