ABB Relion 670 Series Applications Manual page 222

Section 9
Voltage protection
9.1.3 Setting guidelines
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
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.
9.1.3.1 Equipment protection, such as for motors and generators
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
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
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
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
The setting must be below the lowest occurring "normal" voltage and above the highest occurring
voltage during the fault conditions under consideration.
9.1.3.6 Settings for two step undervoltage protection
The following settings can be done for Two step undervoltage protection UV2PTUV (27):
ConnType : Sets whether the measurement shall be phase-to-ground fundamental value, phase-to-
phase fundamental value, phase-to-ground RMS value or phase-to-phase RMS value.
Operation : Disabled or Enabled .
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1MRK 511 401-UUS F
VBase , which normally is set to
Bay control REC670
Application manual
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