Overview


A dip event, also known as a voltage sag, is a temporary decrease in voltage that can occur in an electrical power system. This can happen due to a variety of reasons such as power system faults, sudden changes in load, or the starting of large motors or other equipment.
The basic idea of this event is to detect if the RMS voltage refreshed each half cycle is reduced below specific dip threshold from a user defined RMS value.
The dip threshold is defined as a percentage of the user-defined RMS voltage, typically ranging from 10% to 90%.


Dip Detection Method

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

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


Dip Measurement Specifications

  1. Measurement Method: Detected when RMS voltage refreshed each half cycle falls below the threshold value.
  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: Minimum 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 : Percentage with respect to the declared input voltage.
  2. Event Start : Beginning of a waveform where Urms(1/2) falls below the threshold
  3. Event End :Beginning of a waveform where Urms(1/2) rises above the threshold plus hysteresis
  4. Polyphase system treatment :A dip event starts when any phase is affected and ends when no phase remains below the threshold.
  5. Stored Waveforms: Event waveforms are recorded for each detected dip event



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