ABB ret650 - Second Harmonic Blocking Element

a
b
a>b
OR
|I
OP
|
STx
TRx
AND
Ix>
BLKSTx
BLOCK
Characteristx=DefTime
DirModex=Off
DirModex=Non-directional
DirModex=Forward
DirModex=Reverse
AND
AND
FORWARD_Int
REVERSE_Int
OR
OR
STAGEx_DIR_Int
IEC12000008.vsd
AND
AND
Characteristx=Inverse
Inverse
tx
min
tx
IEC12000008.vsd
IEC12000008 V2 EN
Figure 66: Simplified logic diagram for OC4PTOC
8.2.8 Second harmonic blocking element
A harmonic restrain of the Four step overcurrent protection function OC4PTOC 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 function output signal 2NDHARMD will be set to logical value
one.
a
b
a>b
BLOCK
AND
I
OP
Extract second
harmonic current
component
Extract
fundamental
current component
X
2ndHarmStab
a
b
a>b
a
b
a>b
0.07*IBase
IEC13000014-1-en.vsd
2
N D
H A R M
D
2ndH_BLOCK_Int
IEC13000014 V1 EN
Figure 67: Second harmonic blocking
1MRK 504 135-UEN A Section 8
Current protection
151
Technical manual