Siemens 6MD85, Manual

Page: 619 / 1256

The I0 elimination in phase currents for overcurrent-protection applications can be used in a transformer. This
increases the sensitivity for the 2-phase short circuit on the low-voltage side of the transformer. The following
conditions must be fulfilled:
•
The transformer neutral point current I
Y
is measured and is available for the protection function group.
•
The parameter
Method of measurement
is set to
fundamental comp.
.
With the
I0 elimination
setting, you can switch the I0 elimination function on or off.
Parameter:
Pickup delay
•
Default setting
(_:661:102) Pickup delay
=
0.00 s
This parameter is not visible in the basic stage.
For special applications it is desirable if the current threshold is briefly exceeded, that this will not lead to the
pickup of the stage and starts fault logging or recording. If this stage is used as a thermal overload function,
that is considered a special application.
When using the
Pickup delay
parameter, a time interval is defined during which a pickup is not trigger if
the current threshold is exceeded.
For all short-circuit protection applications, this value is 0.00 s and is considered as a default.
Parameter:
Time dial
•
Default setting
(_:691:101) Time dial
=
1.00
With the
Time dial
parameter, you displace the characteristic curve in the time direction.
The set value for the
Time dial
parameter is derived from the time-grading schedule that has been prepared
for the electrical power system.
Where no time grading and therefore no displacement of the characteristic curve is required, leave the param-
eter
Time dial
at
1
(default setting).
Parameter:
Reset
•
Default setting
(_:691:131) Reset
=
disk emulation
With the
Reset
parameter, you define whether the stage drops out according to the dropout characteristic
curve (in accordance with the behavior of a disk emulation = rotor disk) or instantaneously.
Parameter Value Description
disk emulation
Select this setting if the device is coordinated with electromechanical
devices or other devices which perform a dropout after a disk emulation.
instantaneous
Select this setting if the dropout is not to be performed after disk emulation
and an instantaneous dropout is desired instead.
Parameter:
1-pole operate allowed
•
Default setting
(_:691:11) 1-pole operate allowed
=
no
The parameter must be set for the specific application.
Parameter Value Description
no
The stage always operates 3-pole.
yes
The stage operates phase-selectively. However, tripping by the device
(generated in the trip logic of the Circuit-breaker function group) is always
3-pole because the device does not support phase-selective tripping.
Protection and Automation Functions
7.4 Overcurrent Protection, Phases
SIPROTEC 5, High-Voltage Bay Controller, Manual 619
C53000-G5040-C015-9, Edition 11.2017