ABB Relion 670 Series Applications Manual page 220

Section 9
Voltage protection
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
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:
ConnType : Sets whether the measurement shall be phase-to-earth fundamental value, phase-
to-phase fundamental value, phase-to-earth RMS value or phase-to-phase RMS value.
Operation : Off or On .
UBase (given in GlobalBaseSel ): Base voltage phase-to-phase in primary kV. This voltage is
used as reference for voltage setting. UV2PTUV will operate if the voltage becomes lower than
the set percentage of
RMS . Therefore, always set UBase as rated primary phase-to-phase voltage of the protected
object. For more information, refer to the
The setting parameters described below are identical for the two steps (
the setting parameters are described only once.
Characteristicn : This parameter gives the type of time delay to be used. The setting can be
Definite time , Inverse Curve A , Inverse Curve B , Prog. inv. curve . The selection is dependent on
the protection application.
214
UBase . This setting is used when ConnType is set to PhPh DFT or PhPh
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M13851-50 v3
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n = 1 or 2). Therefore,
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