ABB Relion 670 series, Applications Manual

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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 settings base voltage
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 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.
9.1.3.6 Settings for Two step undervoltage protection
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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 measures selectively phase-to-earth voltages,
or phase-to-phase voltage chosen by the setting
ConnType. The function will operate if the
voltage gets lower than the set percentage of
UBase. When ConnType is set to PhN DFT or PhN
RMS then the IED automatically divides set value for UBase by √3. UBase is used when
ConnType is set to PhPh DFT or PhPh RMS. Therefore, always set UBase as rated primary
phase-to-phase voltage of the protected object. This means operation for phase-to-earth
voltage under:
Section 9 1MRK 505 343-UEN B
Voltage protection
468
Application manual