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Disturbance recorder
Upon detection of a fault condition (triggering), the data storage continues in another
part of the memory. The storing goes on as long as the fault condition prevails - plus a
certain additional time. The length of this additional part is called the post-fault time
and it can be set in the disturbance report. The above mentioned two parts form a dis-
turbance recording. The whole memory acts as a cyclic buffer and when it is full, the
oldest recording is overwritten.
A user-defined name for each of the signals can be programmed in the terminal.
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The recording function can record all analog inputs in the transformer module and up
to 48 binary signals. To maximise the use of the memory, the number of analog chan-
nels to be recorded is user-selectable by programming and can be set individually for
each analog input. The recorded binary signals can be either true binary input signals or
internal logical signals created by the functions.
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The maximum number of recordings stored in the memory is 10. So depending on the
set recording times and the recording of the enabled number of channels, the memory
can contain a minimum of six and a maximum of 10 disturbance recordings comprising
of both header part and data part. But the header part for the last 10 recordings is always
available.
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The terminal has a built-in, real-time clock and calendar. This function is used for time
tagging of the recorded disturbances. The time tagging refers to the activation of the
trigger that starts the disturbance recording.
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The processing of analog signals is handled by a dedicated DSP (digital signal proces-
sor). Other functions are implemented in the main CPU. The memory is shared with
other functions.
The numerical signals coming from the A/D conversion module in serial form are con-
verted to parallel form in a dedicated DSP. The analog trigger conditions are also
checked in the DSP.
A check of the start conditions is performed by searching for a maximum value. This is
a positive peak. The function also seeks a minimum value, which is the negative peak.
When this is found, the absolute average value is calculated. If this value is above the
set threshold level for the overfunction on the channel in question, an overfunction start
on that channel is indicated. The overfunction is indicated with a greater than (>) sign.
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