Setting Notes - Siemens SIPROTEC 4 7VK61 Manual

Setting Notes

2.5.3
General
The voltage protection can only operate if, when configuring the device scope (address 137), it has been set
to Enabled.
The overvoltage and undervoltage stages can detect phase-to-earth voltages, phase-to-phase voltages or the
positive sequence voltages; for overvoltage also the negative sequence voltage, zero-sequence voltage or a
different single-phase voltage can be used. Any combination is possible. Stages that are not required are
switched OFF.
NOTE
i i
For overvoltage protection it is particularly important to observe the setting notes: NEVER set an over-
voltage stage (U
state of permanent pickup which cannot be reset by any measured value operation. As a result, operation
of the device would be impossible!
Please bear in mind that the device is designed for a three-phase voltage transformer connection. If the
connection is only single-phase, internal matching of the measured quantities will not take place. The positive-
sequence component for example is only one third when the connection is to one phase as compared to the
three-phase symmetrical connection. Since it is the smallest of the connected voltages which is relevant for
the phase-earth or phase-phase stages of the undervoltage protection, these stages are not suitable for a
single-phase connection.
Phase-to-earth overvoltage
The phase voltage stages can be switched ON or OFF in address 3701 Uph-e>(>). In addition to this, you can
set Alarm Only, i.e. these stages operate and send alarms but do not generate any trip command. The
setting U>Alarm U>>Trip creates in addition also a trip command only for the U>> stage.
The settings of the voltage threshold and the timer values depend on the type of application. To detect steady-
state overvoltages on long lines carrying no load, set the Uph-e> stage (address 3702) to at least 5 % above
the maximum stationary phase-to-earth voltage expected during operation. Additionally, a high dropout to
pickup ratio is required (address 3709 Uph-e>(>) RESET = 0.98 presetting). This parameter can only be
changed in DIGSI at Display Additional Settings. The delay time T Uph-e> (address 3703) should be a few
seconds so that overvoltages with short duration do not cause tripping.
The U >> stage (address 3704) is provided for high overvoltages with short duration. Here an adequately
ph
high pickup value is set, e.g. the 1
for the delay time T Uph-e>> (address 3705).
Phase-to-phase overvoltage
Basically, the same considerations apply as for the phase voltage stages. These stages can be used instead of
the phase voltage stages or additionally. Depending on your choice, set address 3711 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>
(address 3712) and Uph-ph>> (address 3714).
For the delay times T Uph-ph> (address 3713) and T Uph-ph>> (address 3715) the same considerations
apply as above. The same is true for the pickup ratios (address 3719 Uphph>(>) RESET). The latter setting
can only be altered in DIGSI at Display Additional Settings.
Overvoltage positive sequence system U
You can use the positive sequence voltage stages instead of or in addition to previously mentioned over-
voltage stages. Depending on your choice, set address 3731 U1>(>) to ON, OFF, Alarm Only or U>Alarm
U>>Trip.
SIPROTEC 4, 7VK61, Manual
C53000-G1176-C159-5, Edition 05.2018
, U , U )lower than an undervoltage stage. This would put the device immediately into a
L-E L-L 1
1 / -fold of the nominal phase-to-earth voltage. 0.1 s to 0.2 s are sufficient
2
1
2.5 Under and over-voltage protection (optional)
Functions
107