ABB Relion RES670, Applications Manual

Page: 180 / 382

In many cases, UV2PTUV is a useful function in circuits for local or remote
automation processes in the power system.
9.1.3 Setting guidelines
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All the voltage conditions in the system where UV2PTUV performs its functions
should be considered. The same also applies to the associated equipment, its
voltage and time characteristic.
There is a very wide application area where general undervoltage functions are
used. All voltage-related settings are made as a percentage of the global base value
UBase , which normally is set to the primary rated voltage level (phase-to-phase) of
the power system or the high voltage equipment under consideration.
The trip time setting for UV2PTUV is normally not critical, since there must be
enough time available for the main protection to clear short circuits and earth
faults.
Some applications and related setting guidelines for the voltage level are described
in the following sections.
9.1.3.1 Equipment protection, such as for motors and generators
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The setting must be below the lowest occurring "normal" voltage and above the
lowest acceptable voltage for the equipment.
9.1.3.2 Disconnected equipment detection
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The setting must be below the lowest occurring "normal" voltage and above the
highest occurring voltage, caused by inductive or capacitive coupling, when the
equipment is disconnected.
9.1.3.3 Power supply quality
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The setting must be below the lowest occurring "normal" voltage and above the
lowest acceptable voltage, due to regulation, good practice or other agreements.
9.1.3.4 Voltage instability mitigation
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This setting is very much dependent on the power system characteristics, and
thorough studies have to be made to find the suitable levels.
9.1.3.5 Backup protection for power system faults
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The setting must be below the lowest occurring "normal" voltage and above the
highest occurring voltage during the fault conditions under consideration.
Section 9
1MRK 511 407-UEN C
Voltage protection
174 Phasor measurement unit RES670 2.2 IEC
Application manual