What is a Voltage Swell Event?

A voltage swell is a surge (increase) of voltage above 110 % of the RMS magnitude in your power grid. The duration can be between ½ cycle and one minute. (EN 50160)
Note that not all smart meters have a power quality log. Ask us or your energy meter vendor.

  • events below ½ cycle are transients (not recorded)
  • events from ½ cycle to 30 cycles are instantaneous swells
  • events from 30 cycles to 3 seconds are momentary swells
  • events from 3 seconds to one minute are temporary swells
  • above one minute it's over-voltage (different event)
voltage swell
voltage swell

The graphics shows a five cycle voltage swell, coming from a large load has been turned OFF.

What is the cause for voltage swells?

  • sudden switching OFF of a big consumer (e.g. large electro-motor)
  • a change in the ground reference in floating or unearthed phases

Voltage swell event logging

A voltage dip event consists of:

  • event counter
  • start date/time
  • duration
  • magnitude
    the maximum measured instantaneous voltage in any phase during voltage swell condition

The magnitude percentage (threshold) and the duration can be configured in the settings.
Energy meters have a typical interval time of 500 ms to retrieve the instantaneous voltage.
When the voltage magnitude is set to 110% rms, the power quality event log will be full too fast. So choose a higher value to get reasonable benefit from the event log.
If you don't mind to become annoyed from alert messages, you can also use an additional push event for voltage swell:)

The event starts when the instantaneous voltage rises above the threshold for the given duration.
The event ends when the voltage drops 2 % below the threshold. (We are operating with a 2% hysteresis).

Editor's note: This article was originally published in January 2020 and has been updated for comprehensiveness.

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