Siemens 6MD85 Manual page 235

In some cases, 3-pole disconnection works better for this fault type: If the double line is situated close to a
large generator block (see
double ground faults with a correspondingly high dynamic load of the turbine shaft. For a setting with pickup,
both lines are deactivated since each device detects A-B-E – that is, a multiphase short circuit – upon pickup.
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Figure 5-37
Parameter: Tripping Behavior with 2-Phase Short Circuit
•
Default setting (_:5341:101) Trip at 2ph short circuit = 1-pole, leading phase
With the parameter Trip at 2ph short circuit, you determine whether the short-circuit protection
functions only result in 1-pole tripping in the event of an isolated 2-phase fault (without ground contact),
provided 1-pole tripping is possible and permitted. This enables a 1-phase interrupt cycle for this fault type. In
this case, you determine which of the 2 phases – the leading (1-pole, leading phase) or the trailing
phase (1-pole, lagging phase) – is tripped.
NOTE
i
i
If you want to use this option, bear in mind that phase selection is the same throughout the power system
and at the ends of a line.
If 3-pole tripping is to be executed in the event of this fault type, select the 3-pole setting.
Parameter: Reset of trip command
•
Recommended setting value (_:5341:103) Reset of trip command = with I<
Parameter Value
with I<
with I< &
aux.contact
with dropout
SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017
Figure 5-37). For the generator, both 1-phase ground faults are manifested as
Multiphase Short Circuit on a Double Line Close to the Generator
Description
With this setting, the trip command is reset as soon as the current is removed,
provided the tripping function has dropped out. The most important factor for
recognition of the open circuit breaker is the current falling short of the value
set in the parameter (_:2311:112) Current thresh. CB open.
For this setting not only the current has to be removed, but also the circuit-
breaker auxiliary contact has to report that the circuit breaker is open. This
setting assumes that the setting of the auxiliary contact has been routed via a
binary input (for more information, see
Auxiliary Contacts and Further
You can select the with dropout setting for special applications in which the
trip command does not result in complete interruption of the current in every
case. In this case, the trip command is reset if the pickup of the tripping protec-
tion function drops out.
The setting is useful if the load current in the system cannot be interrupted
during the protection device test and the test current is fed in parallel with the
load current.
5.6 Function-Group Type Circuit Breaker, 1-/3-Pole
5.6.5.3 Acquisition of Circuit-Breaker
Information).
Function-Group Types
235