Setting Notes - Siemens SIPROTEC 7SA522 Manual

2 Functions

2.15.3 Setting Notes

General
Overvoltage Phase-
Earth
Overvoltage
Phase–Phase
Overvoltage Posi-
tive Sequence
System U
1
280
The voltage protection can only operate if it has been set to (QDEOHG during the con-
figuration of the device scope (address ). Compounding is only available if
address  is set to (QDEO Z FRPS.
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 2)).
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 set at address  8SKH! ! to 21 or 2)). In
addition to this you can set $ODUP 2QO\, i.e. these stages operate and send alarms
but do not generate any trip commands.
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
8SKH! stage (address ) 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  8SKH! ! 5(6(7 = 0.98 = preset-
ting). This setting is only possible via DIGSI
7 8SKH! (address ) should be a few seconds so that overvoltages with short
duration may not result in tripping.
The 8SKH!! stage (address ) is provided for high overvoltages with short du-
ration. Here, an adequately high pick-up value is set, e.g. the 1
phase–earth voltage. 0.1 to 0.2 s are sufficient for the time delay 7 8SKH!! (address
).
Basically, the same considerations apply as for the phase undervoltage stages. These
stages may be used instead of the phase voltage stages or be used additionally. De-
pending on your choice, you set address  8SKSK! ! to 21, 2)) or $ODUP
2QO\.
As phase–to–phase voltages are monitored, the phase–to–phase values are used for
the settings 8SKSK! (address ) and 8SKSK!! (address ).
For the delay times 7 8SKSK! (address ) and 7 8SKSK!! (address )
the same considerations apply as above. The same is true for the drop-off ratios (ad-
dress  8SKSK! ! 5(6(7). This latter setting is only possible via DIGSI
"Additional Settings".
The positive sequence voltage stages can be used instead of or in addition to previ-
ously mentioned overvoltage stages. Depending on your choice, you set address
 8! ! to 21, 2)) or $ODUP 2QO\.
, U , U ) lower than an undervoltage stage.
L-E L-L 1
®
at "Additional Settings". The delay time
1
/ -fold of the nominal
2
®
at
7SA522 Manual
C53000-G1176-C155-3