Specifications

Overcurrent Protection SIPROTEC 7SJ80
4/17SIPROTEC Compact · SIEMENS SIP 3.01 · Edition 3
Application examples
Fig. 4/18 Application directional intermittent ground fault protection
Undervoltage-controlled reactive
power protection (QV Protection)
When connecting generating units
to the medium-voltage power
system of the operator, a protective
disconnection device is required
which takes into account frequency
and voltage and also evaluates the
reactive power direction. When the
generating unit draws reactive power
from the operator's power system,
Undervoltage-controlled reactive
power protection (Q> & V<) links
the reactive power with all three
phase-to-phase voltages falling below
a limiting value using a logical AND
operation.
This ensures that generating units dis-
connect from the power system which
additionally burden the power system
during a short circuit or prevent that
the power system is restored when
connecting after a short circuit. The
monitoring of the voltage support
also fulfi lls this function.
Using the criteria mentioned above
the QV protection disconnects the ge-
nerating unit from the power system
after a programmable time.
The QV protection furthermore allows
releasing the re-connection after the
fault has been located and cleared
in the power system and the system
voltage and frequency are stable
again.
4_18_Visio-QU-Schutz-en.pdf
G
3~
G
3~
G
3~
Power transformer
Busbar
Circuit breaker at the power-system connection point
Medium-voltage busbar
Generator step-up transformers
Bus coupler circuit-breaker
Generators
Decoupling protection
with V>>, V<, V<<, f>, f< functionen
Tripping
Further
feeders
Undervoltage
controlled reactive
power protection
*
52
52 5252
50 51 50N 51N
59 27 81
1)
I>, I>> I-TOC
V>, V>>
V<
f>, f>
V<
Q>/
IN>, IN>> IN-TOC
1)
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