ABB RELION 620 Series Technical Manual page 706

Section 8
Power quality measurement functions
700
Statistics recorder
The Statistics recorder module provides readily calculated three-second or ten-minute
values of the selected phase to the percentile calculator module based on the length of the
active observation period. If the observation period is less than one day, the three-second
average values are used. If the observation period is one day or longer, the ten-minute
average values are used.
The maximum three-second or ten-minute mean voltage unbalance is recorded during the
active observation period. The observation period start time PR_STR_TIME, observation
period end time PR_END_TIME, maximum voltage unbalance value during observation
period active, MAX_UNB_VAL and time of occurrence MAX_UNB_TIME are available
through the Monitored data view. These outputs are updated once OBS_PR_ACT
deactivates.
Percentile calculator
The purpose of the Percentile calculator module is to find the voltage unbalance level so
that during the observation time 95 percent (default value of the Percentile unbalance
setting) of all the measured voltage unbalance amplitudes are less than or equal to the
calculated percentile.
The computed output value PCT_UNB_VAL, below which the percentile of the values
lies, is available in the Monitored data view. The PCT_UNB_VAL output value is updated
at the end of the observation period.
If the output PCT_UNB_VAL is higher than the defined setting Unbalance start val at the
end of the observation period, an alarm output PCT_UNB_AL is activated. The
PCT_UNB_AL output remains active for the whole period before the next period
completes.
The BLOCK input blocks the output PCT_UNB_VAL.
Recorded data
The information required for a later fault analysis is stored when the Recorded data
module is triggered. This happens when a voltage unbalance is detected by the Voltage
unbalance detector module.
Three sets of recorded data are available in total. The sets are saved in data banks 1...3. The
data bank 1 holds the most recent recorded data. Older data are moved to the subsequent
banks (1 to 2 and 2 to 3) when a voltage unbalance is detected. When all three banks have
data and a new variation is detected, the latest data set is placed into bank 1 and the data
in bank 3 is overwritten by the data from bank 2.
1MAC504801-IB E
620 series ANSI
Technical Manual