R
Offset
Z1 or Z2
XoffsetZ1
Z1diameter
Z (apparent impedance)
Z1 = Z - (XoffsetZ1 +
Z1diameter/2)
en06000456-2.vsd
IEC06000456 V2 EN-US
Figure 210: Zone measurement in LEXPDIS (40) protection function
The impedance Z1 is constructed from the measured apparent impedance Z and the impedance
corresponding to the centre point of the impedance characteristic (Z1 or Z2). If the magnitude of
this impedance is less than the radius (diameter/2) of the characteristic, this part of the
protection will operate.
If the directional restrain is set Disabled the impedance zone operation will start the appropriate
timer and LEXPDIS (40) will trip after the set delay (
tZ1
or
tZ2
).
If the directional restrain is set Enabled the directional release function must also operate to
enable operation. A new impedance is constructed from the measured apparent impedance Z and
the
XoffsetDirLine
point on the y-axis. If the phase angle of this impedance is less than the set
DirAngle
LEXPDIS (40) function will be released, see figure 211.
1MRK 502 066-UUS B Section 7
Impedance protection
393
Technical manual
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