Siemens 6MD85, Manual

Page: 624 / 1256

You can set the
Threshold (absolute)
parameter to be greater than 1.1 times the
Threshold
value.
Then the stage behaviors are as follows:
•
The stage picks up when the measured current value exceeds the
Threshold (absolute)
value.
•
The stage starts dropout when the measured current value falls short of the
Threshold (absolute)
value by 0.95 times.
•
For measured current values lower than the
Threshold (absolute)
value, no pickup takes place and
consequently the characteristic curve is not processed.
If you set the
Threshold (absolute)
parameter to be less than 1.1 times the
Threshold
value, the
pickup and dropout behaviors are not affected by the
Threshold (absolute)
parameter.
Application and Setting Notes
This stage is structured the same way as the Inverse-time overcurrent protection – advanced stage. The
only differences are described in chapter
7.4.6.1 Description . This chapter provides only the application and
setting notes for setting characteristic curves and for setting the
Threshold (absolute)
parameter. You
can find more information on the other parameters of the stage in chapter 7.4.5.2 Application and Setting
Notes .
Parameter:
Current/time value pairs
(from the operate curve)
With these settings, you define the characteristic curve. Set a current/time value pair for each characteristic-
curve point. The setting depends on the characteristic curve you want to realize.
Set the current value as a multiple of the threshold value. Siemens recommends that you set the
Threshold
parameter to
1.00
in order to obtain a simple relation. You can change the threshold value setting afterwards
if you want to shift the characteristic curve.
Set the time value in seconds. The characteristic curve is shifted via the
Time dial
parameter.
i
i
NOTE
The value pairs must be entered in continuous order.
Parameter:
Time dial
•
Default setting
(_:101) Time dial
=
1
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
Time dial
parameter at
1
.
Parameter:
Reset
•
Default setting
(_:110) 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
In the case of this setting, a dropout characteristic curve has to be set in
addition to the operate curve.
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
but an instantaneous dropout is desired.
7.4.6.2
Protection and Automation Functions
7.4 Overcurrent Protection, Phases
624 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017