9.1.3.5
Backup protection for power system faults
M13851-62 v3
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
M13851-65 v14
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
1MRK 511 401-UUS A
Section 9
Voltage protection
Bay control REC670 2.2 ANSI
243
Application manual
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