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(%)
(
)
3
U
UBase kV
<
×
EQUATION1447 V1 EN-US
(Equation 533)
and operation for phase-to-phase voltage under:
U
(%) UBase(kV)
<
×
EQUATION1990 V1 EN-US
(Equation 534)
The below described setting parameters 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 that 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 of the protection application. It is essential to consider the
minimum voltage at non-faulted situations. Normally this voltage is larger than 90% of
nominal voltage.
tn: time delay of step n, given in s. This setting is dependent of 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 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 trip. By setting
t1Min longer than
the operation time for other protections such unselective tripping can be avoided.
ResetTypeCrvn: This parameter for inverse time characteristic can be set to Instantaneous,
Frozen time, Linearly decreased. The default setting isInstantaneous.
tIResetn: Reset time for step n if inverse time delay is used, given in s. The default value is 25
ms.
kn: Time multiplier for inverse time characteristic. This parameter is used for coordination
between different inverse time delayed undervoltage protections.
ACrvn, BCrvn, CCrvn, DCrvn, PCrvn: Parameters to set to create programmable under voltage
inverse time characteristic. Description of this can be found in the technical reference manual.
CrvSatn: When the denominator in the expression of the programmable curve is equal to zero
the time delay will be infinity. There will be an undesired discontinuity. Therefore, a tuning
parameter
CrvSatn is set to compensate for this phenomenon. In the voltage interval Un<
down to
Un< · (1.0 - CrvSatn/100) the used voltage will be: Un< · (1.0 - CrvSatn/100). If the
programmable curve is used this parameter must be calculated so that:
1MRK 505 343-UEN B
Section 9
Voltage protection
469
Application manual
Содержание Relion 670 series
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