Siemens 6MD86 - Settings

Parameter Value Description
yes
When the transformer inrush-current detection detects an inrush current that
would lead to an operate of the stage, the start of the operate delay and
operate of the stage are blocked.
Select this setting if the device is used on transformers and the threshold
value of the stage is set below the maximum inrush current of the trans-
former. This applies to the overcurrent-protection stage, which is used as a
backup stage with grading time for faults on the undervoltage side of the
transformer.
Parameter: Threshold
•
Default setting (_:4861:3) Threshold = 1.20 A
For setting the threshold value, the same considerations apply as for the non-directional overcurrent protec-
tion function.
For further information, refer to chapter 7.5.4.2 Application and Setting Notes .
Parameter: Dropout ratio
•
Recommended setting value (_:4861:4) Dropout ratio = 0.95
This parameter is not visible for the basic stage.
The recommended setting value of 0.95 is appropriate for most applications.
For high-precision measurements, the setting value of the Dropout ratio parameter can be reduced, for
example to 0.98. If you expect highly fluctuating measurands at the pickup threshold, you can increase the
setting value of the Dropout ratio parameter. This avoids chattering of the stage.
Parameter: Dropout delay
•
Recommended setting value (_:4861:101) Dropout delay = 0 s
This parameter is not visible for the basic stage.
Siemens recommends using the dropout delay of 0 s, since the dropout of a protection stage must be
performed as fast as possible.
You can use the Dropout delay parameter ≠ 0 s to obtain a uniform dropout behavior if you use it
together with an electromechanical relay. This is required for time grading. The dropout time of the electro-
mechanical relay must be known for this purpose. Subtract the dropout time of your own device (see Tech-
nical data) and set the result.
Parameter: Operate delay
•
Default setting (_:4861:6) Operate delay = 0.300 s (for the 1st stage)
The Operate delay to be set is derived from the time-grading chart that has been prepared for the system.
Typical examples of grading times are provided in sections 7.6.9 Application Notes for Parallel Lines and
7.6.10 Application Notes for Directional Comparison Protection .
Settings
Addr.
Parameter C Setting Options Default Setting
General
_:4861:1 Definite-T 1:Mode
•
off
•
on
•
test
off
_:4861:2 Definite-T 1:Operate &
flt.rec. blocked
•
no
•
yes
no
_:4861:105 Definite-T 1:Directional
mode
•
forward
•
reverse
forward
7.7.5.3
Protection and Automation Functions
7.7 Directional Overcurrent Protection, Ground
SIPROTEC 5, High-Voltage Bay Controller, Manual 715
C53000-G5040-C015-9, Edition 11.2017