V
ref
=-3V
0
Operate area
3I
0
RCA = 0º
ROA = 80º
ANSI06000652-2-en.vsd
ANSI06000652 V2 EN
Figure 279: 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.
1MRK 506 369-UUS - Section 9
Current protection
Line distance protection REL670 2.2 ANSI 537
Application manual
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