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:
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.
1MRK 511 407-UEN C
Section 9
Voltage protection
Phasor measurement unit RES670 2.2 IEC
175
Application manual
Summary of Contents for Relion RES670
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