Functions
2.19 Undervoltage and Overvoltage Protection (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
375
The settings of the voltages and times depend on the intended use; therefore no general recommendations for
the settings can be given. For load shedding, for example, the values are often determined by a priority grading
coordination chart. In case of stability problems, the permissible levels and durations of overvoltages must be
observed. With induction machines undervoltages have an effect on the permissible torque thresholds.
If the voltage transformers are located on the line side, the measuring voltages will be missing when the line is
disconnected. To avoid that the undervoltage levels in these cases are or remain picked up, the current criterion
CURR.SUP. Uphe<
(address
3758
) is switched
ON
. With busbar side voltage transformers it can be switched
OFF
. However, if the busbar is dead, the undervoltage protection will pick up and expire and then remain in a
picked-up state. It must therefore be ensured in such cases that the protection is blocked by a binary input.
Phase-to-phase undervoltage
Basically, the same considerations apply as for the phase voltage stages. These stages may replace the phase
voltage stages or be used additionally. Depending on your choice, set address
3761
Uph-ph<(<)
to
ON
,
OFF
,
Alarm Only
or
U<Alarm U<<Trip
.
As phase-to-phase voltages are monitored, the phase-to-phase values are used for the settings
Uph-ph<
(ad-
dress
3762
) and
Uph-ph<<
(address
3764
).
The corresponding time delays are
T Uph-ph<
(address
3763
) and
T Uphph<<
(address
3765
).
The dropout to pickup ratio
Uphph<(<) RESET
can be set in address
3769
. This parameter can only be
altered in DIGSI at
Display Additional Settings
.
If the voltage transformers are located on the line side, the measuring voltages will be missing when the line is
disconnected. To avoid that the undervoltage levels in these cases are or remain picked up, the current criterion
CURR.SUP.Uphph<
(address
3768
) is switched
ON
. With busbar side voltage transformers it can be switched
OFF
. However, if the busbar is dead, the undervoltage protection will pick up and expire and then remain in a
picked-up state. It must therefore be ensured in such cases that the protection is blocked by a binary input.
Undervoltage positive sequence system U
1
The positive sequence undervoltage stages can be used instead of or in addition to previously mentioned un-
dervoltage stages. Depending on your choice, set address
3771
U1<(<)
to
ON
,
OFF
,
Alarm Only
or
U<Alarm U<<Trip
.
Basically, the same considerations apply as for the other undervoltage stages. Especially in case of stability
problems, the positive sequence system is advantageous, since the positive sequence system is relevant for
the limit of the stable energy transmission.
To achieve the two-stage condition, the
U1<
stage (address
3772
) is combined with a greater time delay
T U1<
(address
3773
), and the
U1<<
stage (address
3774
) with a shorter time delay
T U1<<
(address
3775
).
Note that the positive sequence system is calculated according to its defining equation
U
1
=
1
/
3
·|U
L1
+ a·U
L2
+ a
2
·U
L3
|. For symmetrical voltages this is equivalent to a phase-to-earth voltage.
The dropout to pickup ratio
U1<(<) RESET
can be set in address
3779
. This parameter can only be altered
in DIGSI at
Display Additional Settings
.
If the voltage transformers are located on the line side, the measuring voltages will be missing when the line is
disconnected. To avoid that the undervoltage levels in these cases are or remain picked up, the current criterion
CURR.SUP.U1<
(address
3778
) is switched
ON
. With busbar side voltage transformers it can be switched
OFF
.
However, if the busbar is dead, the undervoltage protection will pick up and expire and then remain in a picked-
up state. It must therefore be ensured in such cases that the protection is blocked by a binary input.
Содержание SIPROTEC
Страница 20: ...Contents SIPROTEC 7SD5 Manual C53000 G1176 C169 5 Release date 02 2011 20 ...
Страница 351: ...Functions 2 18 Synchronism and Voltage Check optional SIPROTEC 7SD5 Manual C53000 G1176 C169 5 Release date 02 2011 351 ...
Страница 494: ...Functions 2 27 Command Processing SIPROTEC 7SD5 Manual C53000 G1176 C169 5 Release date 02 2011 494 ...
Страница 640: ...Technical Data 4 27 Dimensions SIPROTEC 7SD5 Manual C53000 G1176 C169 5 Release date 02 2011 640 ...
Страница 657: ...Appendix A 2 Terminal Assignments SIPROTEC 7SD5 Manual C53000 G1176 C169 5 Release date 02 2011 657 7SD5 W ...
Страница 754: ...Appendix A 10 Measured Values SIPROTEC 7SD5 Manual C53000 G1176 C169 5 Release date 02 2011 754 ...
Страница 756: ...Literature SIPROTEC 7SD5 Manual C53000 G1176 C169 5 Release date 02 2011 756 ...
Страница 768: ...Glossary SIPROTEC 7SD5 Manual C53000 G1176 C169 5 Release date 02 2011 768 ...