-3U
0
Operate area
3I
0
RCADir = 0º
ROADir = 80º
IEC06000652-3-en.vsd
IEC06000652 V3 EN-US
Figure 67: 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 faulted feeder only.
RCADir
is set equal
to -90° in an isolated network as all currents are mainly capacitive.
ROADir
is Relay Operating Angle.
ROADir
is identifying a window around the reference
direction in order to detect directionality.
ROADir
is set in degrees. For angles differing more
than
ROADir
from
RCADir
the function is blocked. The setting can be used to prevent
unwanted operation for non-faulted feeders, with large capacitive earth fault current
contributions, due to CT phase angle error.
INCosPhi>
is the operate current level for the directional function when
OpMode
is set
3I0Cosfi
. The setting is given in % of
IBase
. The setting should be based on calculation of the
active or capacitive earth fault current at required sensitivity of the protection.
Section 7 1MRK 511 358-UEN A
Current protection
140
Application manual
To Next Page
Loading...
