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The parameters Dips/Interruptions/Voltage Changes/Swells, Unbalance and
Frequency have a single bar for each parameter representing performance across
three phases.
Most of the Bar Graphs have a wide base indicating adjustable time related limits (for
instance 95% of time within limit) and a narrow top indicating a fixed 100% limit. If
one of both limits is violated, the related bar changes from green to red. Dotted
horizontal lines on the display indicate the positions of 100% limit and the adjustable
limit.
The meaning of the bar graphs with a wide base and a narrow top is explained below
by way of example this is done for the RMS voltage. This voltage for instance has a
nominal value of 220V with a tolerance of ±15% (tolerance range between 187 …
253V). The momentary RMS voltage is constantly monitored by the Analyzer, it
calculates an average from these measuring values across 10 minutes observation
periods, and these averages are compared against the tolerance range.
The 100% limit means that the 10-minute averages must always (i.e. 100% of time or
with 100% probability)be within range. The bar graph will turn to red if a 10-minute
average crosses the tolerance range.
The adjustable limit of for instance 95% (i.e. 95% probability) means that 95% of the
10-minute averages must be within tolerance. The 95% limit is less stringent than the
100% limit. Therefore the related tolerance range usually is tighter. For 220V this for
instance can be ±10% (tolerance range between 198V … 242V).
The bars for Dips/Interruptions/Rapid Voltage Changes/Swells are narrow and
indicate the number of limits violations that occurred during the observation period.
The allowed number is adjustable (for instance to 20 Dips/week). The bar turns to red
if the adjusted limit is violated.
You can use a pre-defined set of limits or define your own. An example of a pre-
defined set is that according to the EN50160 standard.
The table below gives a survey of the aspects of Power Quality Monitoring:
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