Equipment Protection, Such As For Motors And Generators; Disconnected Equipment Detection; Power Supply Quality; Voltage Instability Mitigation - Hitachi Relion 670 Series Applications Manual

Section 9
Voltage protection
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.
VBase (given in GlobalBaseSel): Base voltage phase-to-phase in primary kV. This voltage is used as
reference for voltage setting. UV2PTUV (27) will operate if the voltage becomes lower than the set
percentage of VBase. This setting is used when ConnType is set to PhPh DFT or PhPh RMS. Therefore,
always set VBase as rated primary phase-to-phase voltage of the protected object. For more information,
refer to the Technical manual.
The setting parameters described below are identical for the two steps (n = 1 or 2). Therefore, the setting
parameters are described only once.
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