ABB RELION REX640 Technical Manual page 1420

Section 9
Control functions
1414
If the bus voltage U_BUS is between settings Minimum voltage and Maximum voltage
and the generator voltage U_GEN is greater than the setting Dead voltage value, the
adjusting commands are released. The direction of the adjusting commands depends
on the polarity of ΔU. As an additional condition, both frequencies must be in the
range f ±5 Hz.
n
Maximum voltage
Minimum voltage
Range for no-voltage lines
(Dead bus)
GUID-A6C7C488-0BA2-46E0-82F4-D18F82F58458 V1 EN
Figure 760: Working range of the voltage matcher
If Auto Syn mode is set to either "Semi-automatic synchronizing mode" or "Automatic
synchronizing mode", the voltage raise or lower command pulses are generated from
the function based on the voltage difference across the breaker and AVR response
characteristics. If the voltage difference (ΔU) is negative, it means the reference side
voltage is greater than the running side voltage. So the voltage matching generates the
voltage raise command pulse RAISE_U. If the voltage difference (ΔU) is positive, it
U_BUS
Busbar
Maximum voltage
Nominal voltage (Un), 1 P.U.
Minimum voltage
Dead voltage value
commands blocked
0
1MRS759142 C
U_GEN
Generator
Adjusting
Technical Manual
REX640