Development of a wavelet-based algorithm to detect and determine ...

7.3. MATLAB IMPLEMENTATION 61
7.3.2 Summary
Figure 7.7: Structure chart of the program module
which identifies the disturbance
It is possible to add new pattern for other disturbances. The calculation is the same as
with already integrated disturbances. It is not necessary to find new criteria to detect
these new disturbances, as it is necessary if the identifying is estimated with changing
of the RMS values (for example for a short circuit the criterias are: decreasing voltage
and increasing current, but this can be a load switching also, thus additional criterias
are need for this identifying).
The characteristic pattern described are calculated for a voltage frequency of 60Hz at
an unknown sampling rate. So these pattern have to be adopted for 50Hz and a known
sampling frequncy. Through simulations with Matlab it is known that for getting the
same pattern as described, a sampling rate of 8333,33Hz is necessary. Because this is
not possible, the new pattern have to be calculated. To calculate them, it is necessary
to have very clear disturbance recordings. Of course this is possible with a simula-
tor (power network model or computer based simulator). It is very interesting to do
this simulation with a sampling rate of 12,8kHz, because the Simeas R disturbance
recorder can be used to get the disturbance recordings or 6,4kHz because the distur-
bance recording can be downsampled from the recordings from the Simeas R. The
pattern for several equal disturbances are not the same exactly but in a small range. So
several disturbances for each fault have to be calculated to get the range of the pattern.
In the time for this diploma thesis, it was not possible to make these simulations.
It is obvious to use this small peaks, which are described above for localizing the dis-