Four Residual Overcurrent Steps - ABB REG650 Technical Manual

1MRK 502 034-UEN -
7.2.7.6
Technical Manual

Four residual overcurrent steps

Each overcurrent step uses operating quantity Iop (residual current) as measuring
quantity. Each of the four residual overcurrent steps has the following built-in
facilities:
• Directional mode can be set to Off/Non-directional/Forward/Reverse. By this
parameter setting the directional mode of the step is selected. It shall be noted
that the directional decision (Forward/Reverse) is not made within each
residual overcurrent step itself. The direction of the fault is determined in a
directional element common for all steps.
• Residual current start value.
• Type of operating characteristic. By this parameter setting it is possible to
select inverse or definitive time delay for step 1 and 4 separately. Step 2 and 3
are always definite time delayed. All of the standard IEC and ANSI inverse
characteristics are available. For the complete list of available inverse curves
please refer to section
• Time delay related settings. By these parameter settings the properties like
definite time delay, minimum operating time for inverse curves and reset time
delay are defined.
• Supervision by second harmonic blocking feature (On/Off). By this parameter
setting it is possible to prevent operation of the step if the second harmonic
content in the residual current exceeds the preset level.
Simplified logic diagram for one residual overcurrent step is shown in figure 83.
|I |
OP
INx>
BLKSTx
BLOCK
2ndH_BLOCK_Int
HarmRestrainx=Disabled
DirModex=Off
DirModex=Non-directional
DirModex=Forward
DirModex=Reverse
IEC09000638 V1 EN
Figure 83: Simplified logic diagram for residual overcurrent step n= step 1 and
4
The protection can be completely blocked from the binary input BLOCK. Output
signals for respective step, STINx and TRINx, can be blocked from the binary
input BLKSTn.
"Inverse time characteristics".
Characteristn=DefTime
a
a>b
b
AND
Characteristn=Inverse
OR
OR STEPx_DIR_Int
AND
OR
FORWARD_Int
AND
REVERSE_Int
Section 7
Current protection
tx
OR
Inverse
IEC09000638_1_en.vsd
STINx
161