ABB REC670 Applications Manual page 194

Section 8
Current protection
188
The characteristic for this OpMode when RCADir = 0° and ROADir = 80° is shown
in figure 83.
IEC06000652 V3 EN-US
Figure 83: 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 OpMode.
All the directional protection modes have a residual current release level setting
INRel> 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
UNRel> which is set in % of UBase. 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 earth faults
correctly. The setting shall be much shorter than the set trip delay. In case of
intermittent earth 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 earthed network with a
neutral point resistor as the active current component is appearing out on the
RCADir = 0º
ROADir = 80º
Operate area
3I
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-3U
IEC06000652-3-en.vsd
1MRK 511 401-UEN A
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Bay control REC670 2.2 IEC
Application manual