Siemens 6MD85, Manual

Page: 772 / 1256

•
Measurement of the fundamental component:
This method of measurement processes the sampled current values and filters out the fundamental
component numerically. A DC component is thus eliminated. The RMS value of the fundamental compo-
nent is compared with the set threshold.
•
Evaluation of the unfiltered measurand:
If the current exceeds a preset threshold value by
current ≥ 2·√2·threshold value
this stage will use unfiltered measurands in addition. Thus, very short operate times are possible.
Application and Setting Notes
Parameter:
Threshold
•
Default setting
(_:3901:3) Threshold
=
2.5 A
for I
rated
= 1 A or
12.5 A
for I
rated
= 5 A
Select the value high enough for the protection not to pick up on the RMS value of the inrush current that
occurs when the local circuit breaker is closed. You do not have to consider short-circuit currents flowing
through, because the stage is released only if the circuit breakers are opened at all remote ends of the
protected object or the release was caused by the binary input
>release
.
Parameter:
Dropout ratio
•
Recommended setting value
(_:3901:4) Dropout ratio
=
0.90
The recommended setting value of
0.90
is sufficient for many applications. To obtain extremely accurate
measurements, the dropout ratio can be reduced. If you expect highly fluctuating measurands at the pickup
threshold, you can increase the dropout ratio. This avoids chattering of the tripping stage.
Settings
Addr. Parameter C Setting Options Default Setting
Standard 1
_:3901:1 Standard 1:Mode
•
off
•
on
•
test
on
_:3901:101 Standard 1:Activation
•
on CB closure
•
only with binary signal
•
always active
on CB closure
_:3901:3 Standard 1:Threshold 1 A @ 100 Irated 0.030 A to 35.000 A 10.000 A
5 A @ 100 Irated 0.15 A to 175.00 A 50.00 A
1 A @ 50 Irated 0.030 A to 35.000 A 10.000 A
5 A @ 50 Irated 0.15 A to 175.00 A 50.00 A
1 A @ 1.6 Irated 0.001 A to 1.600 A 10.000 A
5 A @ 1.6 Irated 0.005 A to 8.000 A 50.000 A
_:3901:4 Standard 1:Dropout ratio 0.50 to 0.90 0.90
Information List
No. Information Data Class
(Type) Type
Group indicat.
_:4501:55 Group indicat.:Pickup ACD O
7.11.6
7.11.7
7.11.8
Protection and Automation Functions
7.11 Instantaneous High-Current Tripping
772 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017