Siemens SIPROTEC 7UT613 series, Руководство пользователя

Страница: 256 / 638

2 Functions
256
7UT613/63x Manual
C53000-G1176-C160-2
Figure 2-104 Logic diagram of the undervoltage protection
2.14.2 Setting Notes
General The application of undervoltage protection is only possible in 3-phase protected ob-
jects. Furthermore, it is a prerequisite that the device is connected to a three-phase
voltage transformer set.
Undervoltage protection is only effective and accessible if address
152
was set to
UNDERVOLTAGE Enabled
during configuration of the protection function (section
2.1.3).
Under address
5201 UNDERVOLTAGE
the undervoltage protection
ON
or
OFF
can be
set. Additionally, the command can be blocked if the protection function is enabled
(
Block relay
).
Pickup Values,
Times The undervoltage protection consists of two phases. The equivalent of the phase-
phase voltage is detected, therefore
√
3 · U
1
. The setting is thus effected in interlinked
values.
The U< stage is set slightly below the minimum operational expected voltage under
address
5212 U<
, if the reference values are relevant, under address
5211 U<
when
setting in volts. This setting method depends on whether the voltage transformer set
has been assigned to one side of the main protected object or to any measuring loca-
tion. Normally, 75 % to 80 % of the nominal voltage is recommended; i.e. 0.75 to 0.80
for reference values or 75 V to 80 V for U
N sec
= 100 V (adjusted accordingly in case
of different nominal voltage).