Siemens 6MD85, Manual

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Logic
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Figure 8-21 Logic Diagram of the Current-Balance Supervision
The
Threshold min/max
parameter is the criterion by which unbalance in the phase currents is measured.
The device calculates the ratio between the minimum (I
min
) and the maximum (I
max
) phase current.
Enter the lower limit of the maximum phase current (I
max
) with the parameter
Release threshold
. This
specifies the lower limit of the operating range of this function.
Delay failure indication
If it falls below the balance factor
Threshold min/max
and at the same time the maximum phase current
exceeds the
Release threshold
, the operate delay of the failure indication (parameter
Delay failure
indication
) begins. If both conditions persist during this time, the indication
Failure
is generated.
Blocking the Function
The following blockings reset the picked up function completely:
•
Externally or internally via the binary input signal
>Block function
•
A protection pickup
The pickup signal of a protection function blocks the indication
Failure
.
Application and Setting Notes
Parameter: Threshold min/max
•
Recommended setting value
(_:102) Threshold min/max
=
0.5
The
Threshold min/max
parameter is used to set the ratio between the minimum (I
min
) and the maximum
(I
max
) phase current.
8.3.8.4
Supervision Functions
8.3 Supervision of the Secondary System
SIPROTEC 5, High-Voltage Bay Controller, Manual 961
C53000-G5040-C015-9, Edition 11.2017