Second Harmonic Blocking Element - ABB Relion Technical Manual

Section 8
Current protection
8.1.8
202
|I |
OP
Pickupx
DirModeSelx=Disa bled
DirModeSelx=Non-dire ctional
DirModeSelx=Forward
DirModeSelx=Reverse
ANSI12000008 V3 EN
Figure 90: Simplified logic diagram for OC4PTOC

Second harmonic blocking element

A harmonic restrain of the Four step overcurrent protection function OC4PTOC 51_67
can be chosen. If the ratio of the 2nd harmonic component in relation to the fundamental
frequency component in the residual current exceeds the preset level defined by parameter
2ndHarmStab setting, any of the four overcurrent stages can be selectively blocked by
parameter HarmRestrainx setting. When 2nd harmonic restraint feature is active, the
OC4PTOC 51_67 function output signal 2NDHARMD will be set to logical value one.
BLOCK
Extract second
I
OP harmonic current
component
Extract
fundamental
current component
IEC13000014 V1 EN
Figure 91: Second harmonic blocking
Characteristx=DefTime
a
a>b
b
AND
0-txMin
Inve rse
Characteristx=Inve rse
OR STAGE x_DIR_Int
AND
OR
FORWARD_Int
AND
REVERSE_Int
a
a>b
0.07*IBase
b
a
a>b
b
a
a>b
b
X
2ndHarmStab
1MRK 502 048-UUS A
AND
0-tx
OR
0
AND
0
ANSI12000008-3-en.vsd
ANSI12000008-3-en.vsd
AND
2ndH_BLOCK_Int
IEC13000014-1-en.vsd
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