ABB RELION 670 SERIES REG670 - Setting Guidelines; Disconnected Equipment Detection; Equipment Protection, such as for Motors and Generators; Power Supply Quality

The function has a high measuring accuracy and a settable hysteresis to allow
applications to control reactive load.
In many cases, UV2PTUV (27) is a useful function in circuits for local or remote
automation processes in the power system.
10.1.3 Setting guidelines
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All the voltage conditions in the system where UV2PTUV
(27) 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 VBase,
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 (27) is normally not critical, since there must be
enough time available for the main protection to clear short circuits and ground faults.
Some applications and related setting guidelines for the voltage level are described in
the following sections.
10.1.3.1 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.
10.1.3.2 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.
10.1.3.3 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.
10.1.3.4 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.
Section 10 1MRK 502 071-UUS A
Voltage protection
438 Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
Application manual