7.11. Power Quality Monitoring
Power Quality Monitoring displays a Bar graph screen. This screen show whether important Power
Quality parameters meet requirements. Parameters include: RMS voltages, Harmonics, Flicker,
Dips&Swells/Interruptions/Rapid Voltage Changes, Unbalance, and Frequency.
The length of a bar increases if the related parameter is further away from its nominal value. The bar
turns from green to red if an allowed tolerance requirement is violated.
Use the direction keys to position the cursor on a particular bar and measuring data belonging to that bar
is displayed in the screen header.
Power Quality Monitoring is usually done during a long observation period. The function is entered via
the
【
MONITOR
】
key and start menu to define immediate or timed start of the measurement. Minimum
duration of the measurement is 2 hours, and maximum is 1 week.
The Power Quality parameters RMS voltages, Harmonics, and Flicker have a bar for each phase. From
left to right these bars are related to the phase A (L1), B (L2) and C (L3).
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.
-67-
