Overview


A high frequency event occurs when the measured system frequency rises above a predefined upper threshold set by the user.

The high frequency threshold is defined as a deviation added to the nominal frequency (50 Hz or 60 Hz), configured by the user.


High Frequency Detection Method

The detection algorithm is developed and implemented as follow:

 A high frequency variation event begins when the measured frequency (10/12 cycle) on phase 1 exceeds the upper bound threshold and ends when the measured frequency (10/12 cycle) on phase 1 falls below the threshold minus hysteresis.

High Frequency Measurement Specifications

  1. Measurement Method:
    Digital filtering to extract the fundamental signal, next determine zero crossing, calculating the period of each cycle, accordingly get the frequency of each cycle, and finally estimate the frequency of 10/12 cycle by averaging the frequency each cycle within 10/12 cycle.
  2. Recorded Event Information
    • Frequency Level: measured frequency at event start and end.
    • Start Time: event start timestamp.
    • Event Duration: time interval between Event IN and Event OUT.
    • Worst Case: Maximum value of frequency 10/12 cycle crossed the threshold.
    • Minimum Value: lowest frequency recorded during the event.
    • Maximum Value: highest frequency recorded during the event.
  1. Event Threshold: Defined as a deviation from the nominal frequency (range: 0.1 Hz to 9.9 Hz, step 0.1 Hz).
  2. Event Start: Beginning of a measurement window where the frequency exceeds the threshold.
  3. Event End: Beginning of a measurement window where the frequency  falls below the threshold minus hysteresis (0.1 Hz).
  4. Polyphase system treatment: Not applicable
  5. Stored Waveforms: Event waveforms are recorded for each detected event.

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