Published by Terry Chandler, Director of Engineering, Power Quality (Thailand) Co., Ltd.
Emails: terryc@powerquality.co.th,TChandler@Dranetz.com
The EP1 is Energy Platform has a slightly different time interval for the trended data from the other Dranetz portable products. The PX/PG/PV have a minimum intervals of 1 second, 10 seconds and 1 minute. Note: There are some limitations on the 1 second setting. The EP1 minimum interval is 1 minute. This application note explains the 1 second interval referred to in the manual.
Set up comparison.
Note: These RMS triggers are for voltage during monitoring. Nothing to do with Journal trended values triggers.
Minimum setting is 1 min.
EP1 User Manual States:
Power Values
Power Values Interval – Power parameter values are based upon all cycles during a 1 second
interval. Data is aggregated or summarized into min, max and avg values over the averaging period and stored at the end of the interval. Data measured include watts, power factors, as well as the 1 second RMS.
The EP1 measures every cycle of voltage and current by sampling it 256 times during the cycle. It uses these samples to calculate the minimum RMS value and the maximum RMS value of every cycle. It remembers the largest RMS value of one cycle and the smallest value every 1 second. This 1 second data in NOT brought out to the database, so neither the user interface nor DV6 can access the 1 second values. The 1 second values are aggregated for the time interval the user selects. (1 min, etc) So, the minimum time interval available to graph on the instrument or DV6. See graph below
The EP1 has additional capability based on the 1 second interval data to set thresholds and detect the exact time the value crossed the threshold.
Note: The user can set a threshold for any parameter shown for example harmonic power
When the value of this parameter exceeds the threshold, the EP1 saves the exact time of the event and the values at that time. The event list below shows an example of a Voltage sag and momentary interruption at the exact time. And the time is shown in between the Trend data points. Also, notice the trend data points for harmonics and voltage values are at different intervals.
The screen capture below shows the event graph and the event capture with exact time stamp.
This verifies the EP1 is recording the data in 1 second intervals and storing the event times in sub-second intervals.
Summary:
The EP1 measures and stores a lot of data that can be selected by the user for various reports and graphs. Not all this data is available on the user interface or to DV6. Critical data of abnormal events is available to both user interface and DV6.
website: powerquality.co.th, Application note
Power Quality Blog 