ABB REB670 Applications Manual page 239

1MRK 505 337-UUS -
Application manual
and operation for phase-to-phase voltage under:
< ×
Vpickup (%) VBase(kV)
EQUATION1991-ANSI V1 EN
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 (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 operate undervoltage operation value for step n, given as % of the parameter
VBase. 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 ground 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.
TDn: Time multiplier for inverse time characteristic. This parameter is used for
coordination between different inverse time delayed undervoltage protections.
Section 8
Voltage protection
(Equation 73)
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