Application And Setting Notes - Siemens 6MD85 Manual

Protection and Automation Functions
7.7 Directional Overcurrent Protection, Ground
7.7.7.2

Application and Setting Notes

Apart from the operate curve, this type of stage is identical to the ground-fault protection type with inverse-
time delay according to IEC and ANSI (advanced function type) (see chapter
This section only discusses the nature of the operate curve. For further functionality, refer to chapter
7.7.6.2 Application and Setting
Stage Type Selection
If the operate delay is to be dependent on the current level according to a logarithmic characteristic curve,
select this stage type.
Dynamic Settings: Threshold
•
Default setting (_:3) Threshold = 1.20 A
Define the pickup value corresponding to the application. In doing so, for time-graded stages, the settings of
the superordinate and of the subordinate stages in the time-grading chart must be taken into consideration.
Parameter: Threshold multiplier
•
Default setting (_:116) Threshold multiplier = 1.1
You can use the Threshold multiplier parameter to define the beginning of the characteristic curve on
the current axis (in relation to the threshold value).
General information cannot be provided. Define the value corresponding to the application.
EXAMPLE
Threshold (Secondary current)
Threshold multiplier
Pickup value (Secondary current)
Dynamic Settings: Time dial
•
Default setting (_:6) Time dial = 1.250 s
You can use the Time dial parameter to change the slope of the characteristic curve.
General information cannot be provided. Define the value corresponding to the application.
Parameter: Max. time of the curve
•
Default setting (_:114) Max. time of the curve = 5.800 s
The parameter Max. time of the curve determines the initial value of the characteristic curve (for 3I0 =
Threshold).
General information cannot be provided. Define the value corresponding to the application.
Parameter: Min. time of the curve
•
Default setting (_:113) Min. time of the curve = 1.200 s
The parameter Min. time of the curve determines the lower time limit (at high currents).
General information cannot be provided. Define the value corresponding to the application.
Parameter: Additional time delay
•
Recommended setting value (_:115) Additional time delay = 0 s
You can set an additional current-independent time delay. This additional delay is intended for special applica-
tions.
732
Notes.
I
thresh
I
mul
I = 1.2 A ×1.1 = 1.32 A
PU
7.7.6.1 Description).
= 1.2 A
= 1.1
SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017