Overview 


Inrush current is a transient phenomenon that occurs when electrical equipment is energized, causing a temporary surge in current.

This can lead to voltage fluctuations and temporary disturbances in power quality.

The Inspector device detects and analyzes inrush current events using dedicated algorithms and measurement techniques, providing information about magnitude, duration, and frequency. It also helps identify the impact on voltage and power factor.

This information can be used to identify equipment causing excessive inrush current and take corrective actions, such as adjusting startup timing or using soft starters.

An inrush current event is triggered when the RMS current (updated every half cycle) exceeds a user-defined threshold.

Inrush Current Detection Method

The detection algorithm is developed and implemented as follow: 

  • In single-phase systems, an inrush current event starts when the Irms(1/2) value exceeds the configured threshold and ends when it falls below the threshold minus hysteresis.
  • In polyphase systems, an inrush current event starts when the Irms(1/2) value of any phase exceeds the threshold and ends when all phases fall below the threshold minus hysteresis..

Inrush current Measurement Specifications

  1. Measurement Method: Detected by observing the RMS current calculated using over a 1-cycle time and refreshed each half cycle.
  2. Recorded Event Information:
    • Inrush Current Level: Irms(1/2)I at event start and end.
    • Phase: corresponding phase 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 RMS current recorded during the event.
    • Min Value: lowest RMS current recorded during the event.
    • Max Value: highest RMS current recorded during the event.
  1. Event Threshold: Defined within the current measurement range (from 0 up to the selected current range).
  2. Event Start: Beginning of a half-cycle where the RMS current exceeds the threshold.
  3. Event End: Beginning of a half-cycle where the RMS current falls below the threshold minus hysteresis.
  4. Stored Waveforms: Event waveforms are recorded for each detected inrush current event.



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