Appendix A
Glossary A
A-3
Reference voltage The reference voltage is the voltage that is used for determining
the depth of a dip and the height of a swell.
RMS voltage shape The time function of the RMS voltage change evaluated as a
single value for each successive half period between zero-
crossings of the source voltage.
RMS(1/2) Actual instantaneous RMS voltage: the sliding value of the RMS
voltage measured over an exact period and refreshed each half
period.
Sag See Voltage Dip.
Short interruption The disappearance of the supply voltage for a period of time
typically not exceeding 1 minute.
Swell see Voltage swell
THD Total Harmonic Distortion
Total harmonic current Total RMS value of the harmonic current components.
Voltage dip A sudden reduction of the voltage at a point in the electrical
system, followed by voltage recovery after a short period of time,
from half a cycle to a few seconds.
Voltage fluctuation Series of changes of RMS voltage evaluated as a single value
for each successive half-period between zero-crossings of the
source voltage.
Voltage swell A sudden increase of the voltage at a point in the electrical
system, followed by voltage recovery after a short period of time,
from half a cycle to a few seconds.
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