ABB REG650 Technical Manual page 164

Section 7
Impedance protection
158
XoffsetZ1
Z1diameter
IEC06000456 V2 EN
Figure 72: Zone measurement in LEXPDIS 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 amplitude 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 Off the impedance zone operation will start the
appropriate timer and LEXPDIS will trip after the set delay (tZ1 or tZ2).
If the directional restrain is set On 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 function will be released, see
figure 73.
Offset
Z (apparent impedance)
Z1 = Z - (XoffsetZ1 +
Z1diameter/2)
Z1 or Z2
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