ABB RELION 620 Series Technical Manual page 704

Section 8
Power quality measurement functions
698
Voltage unbalance detector
The three-second average value is calculated and compared to the set value Unbalance
start val. If the voltage unbalance exceeds this limit, the MN_UNB_AL output is activated.
The activation of the BLOCK input blocks MN_UNB_AL output.
Percentile calculation
The Percentile calculation module performs the statistics calculation for the level of
voltage unbalance value for a settable duration. The operation of the Percentile calculation
module can be described with a module diagram.
Observation
3s_MN_UNB
(from Average calculator)
10MIN_MN_UNB
(from Average calculator)
BLOCK
GUID-0190AF77-2DCC-4015-8142-EA6FE5FA2228 V2 EN
Figure 353: Percentile calculation
Observation period
The Observation period module calculates the length of the observation time for the
Statistics recorder sub-module as well as determines the possible start of a new one. A new
period can be started by timed activation using settings Obs period Str time.
A preferable way of continuous statistics recordings can be selected over a longer period
(months, years). With the Trigger mode setting, the way the next possible observation
time is activated after the former one has finished can be selected. When the trigger mode
is selected "Single", it is the single triggering mode, when the trigger mode is selected
"Periodic", it is the periodic triggering mode and when the trigger mode is selected
"Continuous", it is the continuous triggering mode.
In the single triggering mode, only one period of observation time is activated. In the
periodic triggering mode, the time gap between the two trigger signals is seven days. In the
continuous triggering mode, the next period starts right after the former observation
period is completed.
The length of the period is determined by the settings Obs period selection and User Def
Obs period. The OBS_PR_ACT output is an indication signal which exhibits rising edge
(TRUE) when the observation period starts and falling edge (FALSE) when the
observation period ends.
period
Statistics
Percentile
calculator
recorder
1MAC504801-IB E
OBS_PR_ACT
PCT_UNB_AL
620 series ANSI
Technical Manual