ABB REC650 ANSI - Second Harmonic Blocking Element

6.4.8 Second harmonic blocking element
A harmonic restrain of the Four step residual overcurrent protection function EF4PTOC
51N_67N can be chosen. If the ratio of the 2nd harmonic component in relation to the
fundamental frequency component in the residual current exceeds the pre-set level
defined by parameter setting 2ndHarmStab. Any of the four residual overcurrent stages
can be selectively blocked by parameter setting HarmRestrainx. When 2nd harmonic
restraint feature is active the EF4PTOC 51N_67N 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
IEC13000015-1-en.vsd
2
N D
H A R M
D
UseStartValue
IN1>
IN2>
IN3>
IN4>
a
b
a>b
|I
OP
|
t
t=70ms
OR
AN
D
BlkParTransf=On
q
-1
OR
2ndH_BLOCK_Int
IEC13000015 V1 EN
Figure 42: Second harmonic blocking
Section 6 1MRK 511 287-UUS A
Current protection
114
Technical manual