ABB Relion 670 series - Backup Protection for Power System Faults

10.1.3.5 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.
10.1.3.6 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.
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 there is a short
circuit or ground faults in the system. The time delay must be coordinated to the other short
circuit protections.
1MRK 506 369-UUS - Section 10
Voltage protection
Line distance protection REL670 2.2 ANSI 569
Application manual