Functionality; Function Block; Signals - ABB RET650 Technical Manual

Section 8
Current protection
8.9.2
8.9.3
8.9.4
198

Functionality

Negative sequence based overcurrent function DNSPTOC is typically used as
sensitive earth-fault protection of power lines, where incorrect zero sequence
polarization may result from mutual induction between two or more parallel lines.
Additionally, it is applied in applications on cables, where zero sequence impedance
depends on the fault current return paths, but the cable negative sequence impedance
is practically constant.
The directional function is current and voltage polarized. The function can be set to
forward, reverse or non-directional independently for each step. Both steps are
provided with a settable definite time delay.
DNSPTOC protects against all unbalanced faults including phase-to-phase faults. The
minimum start current of the function must be set to above the normal system
unbalance level in order to avoid unwanted operation.

Function block

DNSPTOC
I3P* TRIP
U3P* TROC1
BLOCK TROC2
BLKOC1 START
ENMLTOC1 STOC1
BLKOC2 STOC2
ENMLTOC2 DIROC1
DIROC2
CURRENT
VOLTAGE
UIANGLE
IEC09000125-1-en.vsd
IEC09000125 V1 EN
Figure 89: DNSPTOC function block

Signals

Table 124: DNSPTOC Input signals
Name Type
I3P GROUP
SIGNAL
U3P GROUP
SIGNAL
BLOCK BOOLEAN
BLKOC1 BOOLEAN
ENMLTOC1 BOOLEAN
BLKOC2 BOOLEAN
ENMLTOC2 BOOLEAN
Default Description
- Three phase group signal for current inputs
- Three phase group signal for voltage inputs
0 Block of function
0 Block of over current function OC1
0 Enable signal for current multiplier - step1 (OC1)
0 Block of over current function OC2
0 Enable signal for current multiplier - step 2 (OC2)
1MRK 504 135-UEN A
Technical manual