Settings For Two Step Undervoltage Protection - ABB REG670 Applications Manual

1MRK 502 071-UEN -
10.1.3.6
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual

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 UBase. This setting 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. 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.
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.
OpModen: This parameter describes how many of the three measured voltages should
be below the set level to give operation for step n. The setting can be 1 out of 3, 2 out
of 3 or 3 out of 3. In most applications, it is sufficient that one phase voltage is low to
give operation. If UV2PTUV shall be insensitive for single phase-to-earth faults, 2 out
of 3 can be chosen. In subtransmission and transmission networks the undervoltage
function is mainly a system supervision function and 3 out of 3 is selected.
Un<: Set operate undervoltage operation value for step n, given as % of the parameter
UBase. The setting is highly dependent on the protection application. It is essential to
consider the minimum voltage at non-faulted situations. Normally, this non-faulted
voltage is larger than 90% of the nominal voltage.
tn: time delay of step n, given in s. This setting is dependent on the protection
application. In many applications the protection function shall not directly trip when
there is a short circuit or earth faults in the system. The time delay must be coordinated
to the other short circuit protections.
tResetn: Reset time for step n if definite time delay is used, given in s. The default
value is 25 ms.
tnMin: Minimum operation time for inverse time characteristic for step n, given in s.
When using inverse time characteristic for the undervoltage function during very low
voltages can give a short operation time. This might lead to unselective tripping. By
setting t1Min longer than the operation time for other protections, such unselective
tripping can be avoided.
Section 10
Voltage protection
405