466 Rockwell Automation Publication 1426-UM001J-EN-P - August 2019
Appendix G IEEE 1159 Power Quality Event Classification
The power monitor records each detected power quality event, date and time 
stamp, trip point, min or max value, and associated waveform record, as 
applicable, in the Power Quality Log with an event code of ‘IEEE1159 
_Voltage_Sag’, ‘IEEE1159_Voltage_Swell’ or ‘IEEE1159 _Voltage_Interruption’.
Related Functions
• Long Duration RMS Variations
•Waveform Recording
• Power Quality Log
Long Duration RMS 
Variations (Category 3.0 - 
Undervoltage, 
Overvoltage, Sustained 
Interruptions) (M6 and M8 
model)
A sag or swell with a duration that exceeds one minute is classified as an 
undervoltage or overvoltage, respectively. An interruption with a duration that 
exceeds one minute is classified as a sustained interruption.
Setup
The Sag and Swell thresholds that are described in the Short Duration RMS 
Variations section on page 465
 also determine the operation of undervoltage and 
overvoltage detection.
Operation
When the duration of a sag or swell event exceeds 60 seconds, the new 
classification is recorded in the power quality log with the time stamp of the 
original sag or swell event, and the original sag or swell record in the power 
quality log is updated with a duration of 60 seconds and its associated waveform 
recording.
Status
The Status.Alarms Data Table provides the following tags for monitoring of long 
duration rms variations.
• IEEE1159_Over_Voltage
• IEEE1159_Over_Voltage_V1
• IEEE1159_Over_Voltage_V2
• IEEE1159_Over_Voltage_V3
• IEEE1159_Under_Voltage
• IEEE1159_Under_Voltage_V1
• IEEE1159_Under_Voltage_V2
• IEEE1159_Under_Voltage_V3
The alarm flags are released when the condition no longer exists.