Overview


A swell event is a temporary increase in voltage that can occur in an electrical power system. This can happen due to a variety of reasons such as lightning strikes, switching operations, or sudden disconnection of large loads.

The swell event can cause issues such as equipment damage,insulation breakdown and in extreme cases, fire hazards.

This event is detected when the RMS voltage (updated every half cycle) rises above a predefined swell threshold.

The swell threshold is a percentage of the user RMS entered value and typically ranging from 110% to 200%.


Swell Detection Method

The detection algorithm is based on the IEC 61000-4-30 standard and operates as follows:

  • In single-phase systems, a swell event starts when the Urms(1/2) voltage rises above the swell threshold and ends when it falls below the threshold minus hysteresis.
  • In polyphase systems, a swell begins when the Urms(1/2) voltage of one or more channels is above the swell threshold and ends when the Urms(1/2) voltage on all measured channels is equal to or below the swell threshold minus the hysteresis voltage.


Swell Measurement Specifications

  1. Measurement Method: Detected when the RMS voltage (updated each half cycle) rises above the threshold.
  2. Recorded Event Information:
    • Voltage Level: Urms(1/2) at event start and end (% of nominal).
    • Phase: Corresponding phases at event start and event end.
    • Start Time: Event start timestamp.
    • Frequency: System frequency at event start.
    • Event Duration: Time interval between Event IN and Event OUT.
    • Worst Case: Maximum Urms(1/2) value recorded during the event.
    • Min Value: Minimum RMS voltage recorded for each phase during the event.
    • Max Value: Maximum RMS voltage recorded for each phase during the event.
  1. Event Threshold : Defined as a percentage of the declared input voltage.
  2. Event Start: Beginning of a waveform where Urms(1/2) rises above the threshold.
  3. Event End: Beginning of a waveform where Urms(1/2) falls below the threshold minus hysteresis.
  4. Polyphase system treatment: A swell event starts when any phase exceeds the threshold and ends when no phase remains above it.
  5. Stored Waveforms: Event waveforms are recorded for each detected swell event.


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