ABB RELION RET670, Applications Manual

Page: 570 / 1016

V
ref
=-3V
0
Operate area
3I
0
RCA = 0º
ROA = 80º
ANSI06000652-2-en.vsd
ANSI06000652 V2 EN-US
Figure 281: Characteristic for RCADir = 0° and ROADir = 80°
DirMode is set Forward or Reverse to set the direction of the operation for the
directional function selected by the OpModeSel .
All the directional protection modes have a residual current release level setting
INRelPU which is set in % of IBase . This setting should be chosen smaller than or
equal to the lowest fault current to be detected.
All the directional protection modes have a residual voltage release level setting
VNRelPU which is set in % of VBase . This setting should be chosen smaller than or
equal to the lowest fault residual voltage to be detected.
tDef is the definite time delay, given in s, for the directional residual current protection.
tReset is the time delay before the definite timer gets reset, given in s. With a tReset
time of few cycles, there is an increased possibility to clear intermittent ground faults
correctly. The setting shall be much shorter than the set trip delay. In case of
intermittent ground faults, the fault current is intermittently dropping below the set
value during consecutive cycles. Therefore the definite timer should continue for a
certain time equal to
tReset even though the fault current has dropped below the set
value.
The characteristic angle of the directional functions RCADir is set in degrees. RCADir
is normally set equal to 0° in a high impedance grounded network with a neutral point
resistor as the active current component is appearing out on the faulted feeder only.
RCADir is set equal to -90° in an isolated network as all currents are mainly capacitive.
Section 9
1MRK 504 163-UUS A
Current protection
564 Transformer protection RET670 2.2 ANSI
Application manual