Setting Notes - Siemens Siprotec 7VK61 Manual

Functions
2.5 Under and over-voltage protection (optional)
2.5.3

Setting Notes

General
The voltage protection can only operate if it has been set to 137 during the configuration of the device scope
(address Enabled).
The overvoltage and undervoltage stages can detect phase-to-earth voltages, phase-to-phase voltages or the
symmetrical positive sequence system of the voltages; for overvoltage also the symmetrical negative sequence
system, zero sequence voltage or a different single-phase voltage can be used. Any combination is possible.
Detection procedures that are not required are switched OFF.
Note
For overvoltage protection it is particularly important to observe the setting hints: NEVER set an overvoltage
stage (U , U
L-E
permanent pickup which cannot be reset by any measured value operation. As a result, operation via DIGSI or
via the front display would be impossible due to the permanent pickup!
Please bear in mind that the device is designed for a three-phase voltage transformer connection. If the con-
nection is only single-phase, internal matching of the measured quantities will not take place. The positive-se-
quence 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-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-earth voltage expected during operation. Additionally, a high dropout to pickup
ratio is required (address 3709 Uph-e>(>) RESET = presetting). This parameter can only be altered 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 may not result in tripping.
>> stage (address 3704) is provided for high overvoltages with short duration. Here an adequately high
The U
ph
pickup value is set, e.g. the 1
time T Uph-e>> (address 3705).
Phase-phase overvoltage
Basically, the same considerations apply as for the phase voltage stages. These stages may be used instead
of the phase voltage stages or be used 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 dropout ratios (address 3719 Uphph>(>) RESET). The latter setting
can only be altered in DIGSI at Display Additional Settings.
106
, U ) lower than an undervoltage stage. This would put the device immediately into a state of
L-L 1
1
/ -fold of the nominal phase-earth voltage. 0.1 s to 0.2 s are sufficient for the delay
2
SIPROTEC, 7VK61, Manual
C53000-G1176-C159-3, Release date 05.2009