Appx.6
Explanation of Power Quality Parameters and Events
Interharmonics
Waveform and event
Frequency components that are not a
whole multiple of the fundamental wave
caused by distortions of the voltage and
current waveforms due to any of the
following:
• Static frequency conversion equipment
• Cycloconverters
• Scherbius machines
• Induction motors
• Welder machines
• Arc furnaces
Primary fault Displacement of the voltage waveform zero-cross may damage equipment, cause it to
malfunction, or degrade its performance.
Event that may be
detected
Total harmonic distortion (THD) (voltage)
Measurement Items Interharmonic voltage, interharmonic current
Inrush current
Waveform and event
Voltage waveform
Current waveform
Inrush current is a large current that ows
momentarily, for example, when the electric
equipment is turned on.
Primary fault Inrush current may cause the following events:
• Fusing of power switch contact or relay
• Fuse blowouts
• Circuit breaker disconnections
• Failure of rectifying circuits
• Supply voltage instability
• Equipment sharing the same power supply stops operating or resets due to supply
voltage instability
Event to be detected Inrush current
Flicker (Available after the rmware update)
Waveform and event
Voltage uctuation caused by blast furnace,
arc welding, and thyristor control loads.
This causes icker in light bulbs etc.
Primary fault Because this phenomenon reoccurs regularly, it may cause the light to icker or the
device to malfunction.
Large icker values indicate that most people would nd the ickering of lighting
unpleasant.
Measurement Items ∆V10 icker, IEC icker Pst, Plt
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