Setting Notes - Siemens siprotec 7SD5 User Manual

2 Functions

2.17.3 Setting Notes

The voltage protection can only operate if it has been set to Enabled during the con-
General
figuration of the device scope (address 137). Compounding is only available if
address 137 is set to Enabl. w. comp..
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 ov-
ervoltage 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
This would put the device immediately into a state of permanent pickup which cannot
be reset by any measured value operation. As a result, the device would remain out
of service!
The phase voltage stages can be switched ON or OFF in address 3701 Uph-e>(>).
Overvoltage
In addition to this, you can set Alarm Only, i.e. these stages operate and send
Phase–Earth
alarms but do not generate any trip command The setting creates in addition also a
trip command for these stages.
The settings of the voltage threshold and the timer values depend on the type of ap-
plication. If steady-state overvoltages are to be detected on long unloaded lines, the
Uph-e> stage (address 3702) is set to at least 5 % above the maximum stationary
phase–to–earth voltage that is to be expected in operation. Additionally, a high drop-
off to pick-up ratio is required (address 3709 Uph-e>(>) RESET = 0.98 = preset-
ting). This setting is only possible via DIGSI
T Uph-e> (address 3703) should be a few seconds so that overvoltages with short
duration may not result in tripping.
The Uph-e>> stage (address 3704) is provided for high overvoltages with short du-
ration. Here an adequately high pickup value is set, e.g. the 1
phase-earth voltage. 0.1 s to 0.2 s are sufficient for the delay time T Uph-e>> (ad-
dress 3705).
Overvoltage Basically, the same considerations apply as for the phase voltage stages. These
Phase–Phase stages may be used instead of the phase voltage stages or be used additionally. De-
pending on your choice, set address 3711 Uph-ph>(>) to ON, OFF, Alarm Only or .
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 (ad-
dress 3719 Uphph>(>) RESET). This parameter can only be altered with DIGSI
under Additional Settings.
Overvoltage Posi- You can use the positive sequence voltage stages instead of or in addition to previous-
ly mentioned overvoltage stages. Depending on your choice, set address 3731
tive Sequence
U1>(>) to ON, OFF, Alarm Only or .
System U
1
334
, U , U ) lower than an undervoltage stage.
L-E L-L 1
®
at "Additional Settings". The delay time
1
/ -fold of the nominal
2
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7SD5 Manual
C53000-G1176-C169-1