ABB REG650 Technical Manual page 115

1MRK 502 043-UUS B
Technical Manual
common trip TRIP are issued. This feature is called the sensitive negative
sequence differential protection.
5. If a pickup signal is issued in a phase (see signal PU_A), even if the fault has been
classified as an external fault, then the instantaneous differential current of that
phase (see signal ID_A) is analyzed for the 2
the blocks with the text inside: 2nd Harmonic; Wave block and 5th Harmonic). If
there is less harmonic pollution, than allowed by the settings I2/I1Ratio, and I5/
I1Ratio, (then the outputs from the blocks 2nd harmonic and 5th harmonic is 0)
then it is assumed that a minor simultaneous internal fault must have occurred.
Only under these conditions a trip command is allowed (the signal TRIPRES_A is
= 1). The cross-block logic scheme is automatically applied under such
circumstances. (This means that the cross block signals from the other two phases
B and C is not activated to obtain a trip on the TRIPRES_A output signal in figure
38)
6. All pickup and blocking conditions are available as phase segregated as well as
common signals.
IDMAG_A Diff
IDiffAlarm
IDMAG_B Diff
IDiffAlarm
IDMAG_C Diff
IDiffAlarm
ANSI06000546 V2 EN
Figure 42: Differential current alarm logic
a
a>b
b
a
a>b
b
a
a>b
b
Differential protection
nd th
and the 5 harmonic contents (see
0-tAlarmDelay
&
0
ANSI06000546-2-en.vsd
Section 6
IDALARM
109