3WL air circuit breakers
3.3 Metering functions
3WL/3VL circuit breakers with communication capability - PROFIBUS
48 System Manual, 03/2011, A5E01051353-02
Trigger event
Tripping operations, alarm signals and threshold warnings are available as trigger events so
that the voltage wave for an undervoltage trip can be recorded. The trigger event can be set
individually for each waveform buffer. In addition, the position in the stopped waveform buffer
at which the trigger should be located can be stored.
The relationship between pre-history and post-history can be set in this way. If the pre-
history of the trigger event is to be analyzed, the position can be set to 80%, for example. If
the event occurs, 0.8 of a second of pre-history and 0.2 of a second of post-history are
available in the waveform buffer, and an available COM15 adds a time stamp to the trigger
event.
Data export
The extensive analysis data (approximately 25 KB per waveform) can be downloaded and
analyzed with Switch ES Power and the display of the ETU76B. There are different zoom
options and export functions available depending on the program.
When downloading, you must first select which channels are necessary, since approximately
1 minute per channel is required for downloading. The time duration is explained partly
because, as well as recording the measured values, calculating the harmonics, and the
extended protection function, the metering function also has to carry out tasks with higher
priority and thus the communication process takes longer. Also, a large volume of data is
transferred. The progress of this process is indicated by a progress bar in Switch ES Power.
3.3.2 Voltage transformer
For safety reasons, a voltage transformer is used to operate the metering function PLUS.
This prevents voltage signals of up to 1 kV reaching the back of the ETU direct via the
auxiliary conductor connections.
The voltage transformer converts the high primary voltage to a secondary voltage between
100 V and 120 V, depending on the version.
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