3WL air circuit breakers
3.4 Functions and parameters
3WL/3VL circuit breakers with communication capability - PROFIBUS
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System Manual, 03/2011, A5E01051353-02
3.4.4
Threshold values
As well as the load management facility (load shedding/load pick up), the metering function
PLUS provides another option for automatic monitoring of operating data and for generating
an alarm when a normal status is exited.
In general, the same monitoring functions are available for the threshold values as for the
extended protection function. The greatest difference, however, is that the violation of a
threshold never results in a tripping operation.
Together with the extended protection function, two thresholds can thus be defined (e.g. for
overvoltage). With the lower of the two, only an alarm is generated via the threshold function
(e.g. > 410 V), and if the voltage continues to rise, a tripping operation is triggered (e.g.
> 430 V).
3.4.5
Lower limit of power transmission
Despite extremely high accuracy in recording the current over a large dynamic range, a fault
current is generated with a switch with high rated current (e.g. 4000 A) at 1% accuracy in the
lower range. One possible result of this is that when the switch is off (main contacts opened),
a current flow of up to 40 A can be displayed and transferred via the communication system.
To avoid this, it is possible to convert all recorded current values less than or equal to this
parameter to zero using the parameter "Lower limit of power transmission". The factory
setting for this value is 50 A. This means all values less than or equal to 50 A will appear on
the display as 0 and will be used as 0 for internal calculations (power), and transferred as 0
via the communication system.
If this parameter is changed to 0, this function is switched off and all recorded measured
current values are used direct.
The parameter for this can be found in the parameter tree of Switch ES Power
under "Device parameters – Switch – Measured value settings".
3.4.6
Direction of incoming supply
The direction of "flow" of the energy at a given time, or how much energy has "flowed" in
both directions until now, is important above all for coupling switches. It is necessary here to
define a "normal direction". This can be either "top down" or "bottom up".
Depending on this, the measured active power values have a positive sign (in normal
direction) or a negative sign (in reverse direction). The measured currents, by contrast,
always have a positive sign!
The transferred energy values flow into two counters, active energy in the normal direction
and active energy in the reverse direction. Neither energy counter has a sign.
