ABB RELION REX640, Техническое руководство, Страница: 1194 / 1960

5.7.2 Function block
Figure 681: Function block
5.7.3 Functionality
The fault locator function SCEFRFLO provides impedance-based fault location. It is
designed for radially operated distribution systems, and it can locate short circuits
in all kinds of distribution networks. Earth faults can be located in effectively
earthed and in low-resistance or low-reactance earthed networks. With certain
limitations, SCEFRFLO can also be used for locating an earth fault in unearthed
distribution networks. Moreover, SCEFRFLO can be applied to compensated
(resonant earthed) networks where an earth-fault current raising resistor is
connected in parallel with the arc suppression coil. The location of the continuous
low-ohmic earth fault can be determined by using the switching of the parallel
resistor of the coil during an earth fault.
The fault distance calculation is based on the locally measured fundamental
frequency current and voltage phasors. The full operation of SCEFRFLO requires
all phase currents and phase-to-earth voltages to be measured.
The fault distance estimate is obtained when SCEFRFLO is externally or internally
triggered.
5.7.4 Analog channel configuration
SCEFRFLO has three analog group inputs which must be properly configured.
Table 1147: Analog inputs
Input Description
I3P Three-phase currents
U3P Three-phase voltages
URES
1
Residual voltage (measured), necessary when the phase-to-
phase voltages are measured and Phase voltage Meas is set
to "Accurate"
See the preprocessing function blocks in this document for the possible
signal sources. The
GRPOFF
signal is available in the function block called
Protection.
There are a few special conditions which must be noted with the configuration.
1
Can be connected to
GRPOFF
if
Phase voltage Meas is set to "Ph-to-ph without Uo"
Protection related functions 1MRS759142 F
1194 REX640
Technical Manual