Siemens 7SJ85 - Settings

Set the Negative-sequence voltage stage so that it does not generate a fault when it picks up and does not
initiate tripping. The Overcurrent-protection stage generates a fault indication. The pickup of the Negative-
sequence voltage stage is used as the release criterion because the Short-circuit function must be released
immediately when the Negative-sequence voltage stage has picked up. The time delay is thus not relevant
and can be left at the default setting.
You implement the release of the Overcurrent-protection stage using a logic block chart. An inverter links
the pickup of the Negative-sequence voltage stage with the Overcurrent-protection stage blocking.
[loinvert-020412-01.tif, 1, en_US]
Figure 6-191 Linking the Pickup of the Negative-Sequence Voltage Stage
Stage Setting Values
Secondary Threshold Value Time Delay Dropout Ratio
1 5.800 V 3.00 s 0.95
The second stage is not needed. It is deleted or remains off.
Example 2:
A negative-sequence voltage in the auxiliary system of the power plant causes negative-sequence currents on
motors. This leads to a thermal overload of the rotors. The following estimation can be used as a basis: 1 %
negative-sequence voltage can lead to approximately 5 % or 6 % negative-sequence current.
A negative-sequence voltage can be caused by a broken conductor on the high-voltage side. If a negative-
sequence voltage occurs, this can, for example, initiate a switching of the infeed in order to prevent a protec-
tion trip of an unbalanced-load protection of the motors.
Siemens recommends using multiple stages for a better grading, whereby a sensitive setting of the threshold
permits an increased tripping delay.
For a reference, only 2 stages are discussed.
The first stage has a pickup threshold of 10 % with a time delay of 1.5 s. The second stage has a pickup
threshold of 3 % with a time delay of 8 s, see Table 6-14. Further, it is assumed that the voltage transformer is
well adapted to the rated voltage.
[fo_OVP_V2_SecondaryThreshold2, 1, en_US]
Table 6-14 Recommended Settings
Stage Threshold Operate Delay
Stage 1 5.800 V 1.50 s
Stage 2 1.730 V 8.00 s
Settings
Addr.
Parameter C Setting Options Default Setting
Stage 1
_:271:1 Stage 1:Mode
•
off
•
on
•
test
off
_:271:2 Stage 1:Operate &
flt.rec. blocked
•
no
•
yes
no
_:271:3 Stage 1:Threshold 0.300 V to 200.000 V 5.800 V
6.26.4.3
Protection and Automation Functions
6.26 Overvoltage Protection with Negative-Sequence Voltage
SIPROTEC 5, Overcurrent Protection, Manual 719
C53000-G5040-C017-8, Edition 07.2017