Elspec G3500 BlackBox, User And Installation Manual

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Fixed Quality vs. Fixed Ratio
The most important parameter defining the actual compression ratio, (which determines the amount
of storage required and maximum time continuous data can be stored) is a PQZIP Threshold value or
Tolerance as it referred on the WEB page. The Tolerance defines what change in an individual
harmonic would be defined as significant enough to be stored and reproduced afterwards.
The tolerance value is calculated in percentage to the full scale or nominal reading for the specific
channel. It is assumed that changes within 0.1% of nominal would have no importance in further
power quality investigation, and the values within that range are averaged to store the
representative value only. The basic and factory default tolerance value is normally defined as
0.1%. However, on some sites/networks that value can still be considered too low, for example, a
highly fluctuating load or voltage lines. It is most likely that a user would prefer increasing a
tolerance value for currents or voltages or even both in order to achieve better compression ratios
on highly polluted network locations.
Configuring fixed ratio:
The Portable BLACKBOX provides the possibility of automatic adjustment of the actual tolerance
value presuming a compression ratio defined as amount of data being stored per month. This option
is called
Fixed Ratio . When selected, the user is requested to define the amount of data to be
stored per month ( Monthly Ratio ) in MB. Usually, slight voltage spectral changes have higher
importance than current changes. Therefore, the amount of data which could be stored for voltages
may be determined as greater than for currents. The
V/I Relation parameter defines the
relationship between the data (a part of the Monthly Ratio) reserved for voltage. If the voltage
portion is larger than currents, the system will define a tighter tolerance for voltages than for
currents.

Access your Portable BLACKBOX Unit's PQZIP Configuration via the
PQZIP Recording Tab

In the PQZIP Configuration section, go to the PQZIP Mode & from the drop-down selection
select Fixed Ratio followed by . The PQZIP Configuration window will now
open :

Define the amount of data stored per month, by entering the MB Value in the Monthly Ratio
text box

Set the appropriate V/I Relation value with the

To apply your changes select