During a customer’s trial of the PQ-Box 100 and the WinPQ Mobile software, we asked about the common customer voltage complaint investigations they were performing with their existing loggers.
It appears that a number of their evaluations involved a process of manually “eyeballing” the measurement logs/data– that is, the voltage trace/ graph was displayed with a limit line set up on the screen and the data scrolled to see where the graph exceeded the limit. While WinPQ mobil certainly supports this manual method, it does offer much more powerful and automated evaluation based on EN 50160 style criteria. The flexibility in the PQ-Box 100 that suits many Australian and NZ users is that the evaluation limits can be setup by the user to match those used by each utility – it’s our observation that there appears to be little standardisation in following the actual PQ standards.
Example Customer Criteria:
Sites will not be investigated for corrective action where the 1st and 99th percentile values of the measured voltages over the measurement interval are between the statutory limit. [Statutory Limit = 240 V +/- 6 %]
Figure 1. PQ-Box 100 statistical limit setup.
Figure 2. PQ-Box 100 nominal voltage setup.
Here, simply the statistical limits were altered from 5 and 95 % to 1 & 99 % (Figure 1). The Statutory Limit was entered as the target nominal voltage (Figure 2). Finally the evaluation criteria of 6 % was entered (Figure 3).
Figure 3. PQ-Box 100 evaluation critera.
Figure 4 shows the EN/IEC report summary, this provides a high level overview. This normalised graph provides a view of the data in relation to the upper limits. The red bar portion is the 99 % value, the blue is the 1 % value. Simply, if the bar graph exceeds the horizontal limit line, then one of the limits has been exceeded. This EN/IEC report summary is normally the first step, to get an overview of power quality.
Figure 4. PQ-Box 100 EN automated reporting.
The actual values are shown in Figure 5. It can quickly been seen if the voltage exceeds the limits, and by what amount. In this example, corrective action was required as the 99 percentile value (260.42 V) exceeds the limit (254.4 V)
Figure 5. PQ-Box 100 nominal voltage setup.
Second customer evaluation:
…..requires the determination if two or more 10 minute intervals exceed the limits, and are consecutive, or in regular occurrence.
Here two methods were proposed. One was similar to their existing manual eyeball method, the second more rigorously following the use of measuring intervals.
The Swell trigger was set to 6 % (Also shown in Figure 3). The table of all swell events was sorted according to duration, to determine if swells exceed 10 minutes in duration. While the swell reports the exact duration, the event is not synchronised to a 10 minute interval as referred in the evaluation criteria, so the second method was also proposed.
The second method used the “Slow voltage event”, which is strictly evaluated over the 10 minute measuring interval. If the voltage exceeds the limit for the full 10 minute period, then an event is generated in that log. At the end of the measurement the log count automatically provides the count of the number of events. The actual log can be reviewed to determine if the events are consecutive or regular in occurrence (Figure 6).
Figure 6. PQ-Box 100 table reports.
The team at HV Power will be pleased to help you understand where the automated evaluation criteria of the PQ-Box 100 can be put to use in your network for customer voltage complaint evaluations.