500 Rockwell Automation Publication 1426-UM001J-EN-P - August 2019
Glossary
Current Overload A higher than normal flow of current through a conductor or device that exceeds
the rating of the conductor or device.
Current Transformer (CT) A transformer, intended for measuring or control purposes, which are designed to
have its primary winding connected in series with a conductor carrying the
current to be measured or controlled. CT's step down high currents to lower
values that can be used by measuring instruments.
Current Transformer Ratio The ratio of primary amperes divided by secondary amperes.
Data Flagging Marking a measured data parameter as potentially inaccurate because the
measurement was made during a power quality event.
Data Table Power monitor data is organized in data tables similar to data tables found in an
SLC 5/03 Programmable Controller. The detailed data table definitions are
covered in Appendix A
.
DC Offset DC offset occurs when an AC waveform has been distorted in a manner that
results in a non-zero sum of the waveform values over a one cycle interval.
Demand Hours The equivalent number of hours in a month during which the peak demand is
fully used. In other words, if energy consumption for the current month is X
kwhr and the peak demand is Y kW, then the demand hours is equal to X/Y
hours. The higher the number of demand hours, the better the demand leveling
situation, and the more effectively demand is being used.
Demand Interval Demand charges are based on peak demand over a utility specified time interval,
not on the instantaneous demand (or connected load) at any given moment.
Typical demand intervals are 15, 20, and 30 minutes.
Dip See Sag
.
Duration For purposes of power quality measurement, duration is the elapsed time from
the beginning of a power quality event to the end of that event.
EN 50160 European standard for ‘Voltage characteristics of electricity supplied by public
electricity networks’. Defines acceptable variations in the utility supplied voltage.
EN 61000-4-7 European standard for Testing and measurement techniques - General guide on
harmonics and interharmonics measurements and instrumentation, for power
supply systems and equipment connected thereto.
EN 61000-4-15 European standard for Testing and measurement techniques - Flickermeter -
Functional and design specifications.
EN 61000-4-30 European standard that defines testing and measurement techniques for power
quality measurement methods.
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