ABB RED670 Handbuch Seite 430

Abschnitt 4
IED Anwendung
426
UBase: Base voltage phase to phase in primary kV. This voltage is used as
reference for voltage setting. It can be suitable to set this parameter to the rated
primary voltage of the voltage transformer where the current measurement is made.
The overvoltage protection function measures the phase to earth voltages, or phase
to phase voltages as selected. The function will operate if the voltage gets higher
than the set percentage of the set base voltage UBase. This means operation for
phase to earth voltage over:
< ×
U (%) UBase kV ( )
EQUATION1447 V1 DE
and operation for phase to phase voltage under:
> ×
U (%) UBase(kV)
EQUATION1993 V1 DE
The below described setting parameters are identical for the two steps. 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/Inverse Curve C/Prog. inv.
curve. The choice is highly dependent of the protection application.
OpModen: This parameter describes how many of the three measured voltages that
should be above the set level to give operation. The setting can be. 1 out of 3/2 out
of 3/3 out of 3. In most applications it is sufficient that one phase voltage is high to
give operation. If the function shall be insensitive for single phase to earth faults 1
out of 3 can be chosen, because the voltage will normally rise in the non-faulted
phases at single phase to earth faults.
UnPickup'n': Set operate overvoltage operation value for step n, given as % of
UBase. The setting is highly dependent of the protection application. Here it is
essential to consider the Maximum voltage at non-faulted situations. Normally this
voltage is less than 110% of nominal voltage.
tn: time delay of step n, given in s. The setting is highly dependent of the protection
application. In many applications the protection function has the task to prevent
damages to the protected object. The speed might be important for example in case
of protection of transformer that might be overexcited. The time delay must be co-
ordinated with other automated actions in the system.
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. For very high voltages the overvoltage function, using inverse time
characteristic, can give very short operation time. This might lead to unselective
3
1MRK 505 186-UDE B
(Gleichung 332)
(Gleichung 333)
Applikationshandbuch