Published by Terry Chandler, Director of Engineering, Power Quality Thailand LTD/Power Quality Inc., USA.
E-mail: terryc@powerquality.org, terryc@powerquality.co.th
An example is the Dranetz HDPQ family, the PX-5 family and the 61K family.
The IEC standard for frequency measurement calculation and accuracy is
This specifies the time of the reference channel is measured for 10 seconds. That value is then divided by 10. To get a 1 second value. The one second values are accumulated per the user setup of the meter.
The user selects what channel the instrument records the frequency as shown below
Selecting the standard presets, the default values to that standard.
The user also may change the time scale for the data accumulation. Shown here as 1 second vs the standard of 10-minute values.
Note: there are 4 independent time bases in the Dranetz instruments. The user can time base desired. The IEC 61000-4-30 has different time bases depending on the parameter. The default of the time bases is set when choosing the standard during the setup.
This setting of the time base sets the period for the data storage for the various parameters. The values are calculated per the IEC or IEEE standard and every second the min and max value is stored of the previous second. (note: If the 10-minute time base is selected the Min/Max and average of each RMS value is saved.
As shown below using DV 7 software the user can display Freq (max and Min) if the 1 second time-based is selected
The user can also trigger on a change of frequency and instrument will store time of day and value of frequency at the time of out of specification limit was exceeded.
The results of frequency data recorded is shown below in graphic format and Date Time Value CSV format
Note: While the values are stored every second for frequency. The value is the result of the 10 second calculation every second. This means the frequency value is the previous 10 seconds of the frequency updated every second.
Please feel free to leave a question in the comments section or contact Terry Chandler, terryc@powerquality.org or terryc@powerquality.co.th
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