Theory Of Operation - ABB REG650 Technical Manual

1MRK 502 034-UEN -
6.1.6.4
Technical Manual
arguments by the parameter ImpedanceAng. The setting ImpedanceAng is common
for all three zones.
IEC10000176 V1 EN
Figure 61: Mho, offset mho characteristic for Zone 1 with setting parameters
Z1Fwd, Z1Rev and ImpedanceAng
The measuring loops can be time delayed individually by setting the parameter tZx
(where x is 1-3 depending on selected zone). To release the time delay, the
operation mode for the timers, OpModeZx (where x is 1-3 depending on selected
zone), has to be set to On. This is also the case for instantaneous operation.
The function are blocked in the following ways:
• Activating of input BLOCK blocks the whole function.
• Activating of the input BLKZ (fuse failure) blocks all output signals.
The activation of input signal BLKZ can be made by external or internal fuse
failure function.

Theory of operation

The mho algorithm is based on the phase comparison of a operating phasor and a
polarizing phasor. When the operating phasor leads the polarizing phasor by more
than 90 degrees, the function operates and gives a trip output.
Impedance protection
ImpedanceAng
IEC10000176-1-en.vsd
Section 6
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