Backup Protection For Power System Faults - ABB REC670 Applications Manual

1MRK 511 401-UUS A
9.1.3.5
9.1.3.6
Bay control REC670 2.2 ANSI
Application manual

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.
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.
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 (27) shall be insensitive for single phase-to-ground
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.
Pickupn: Set pickup undervoltage operation value for step n, given as % of the
parameter VBase. 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
Section 9
Voltage protection
M13851-62 v3
M13851-65 v14
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