{"id":21813,"date":"2026-01-15T23:52:51","date_gmt":"2026-01-15T23:52:51","guid":{"rendered":"https:\/\/circuitenergy.ca\/staging\/8539\/?page_id=21813"},"modified":"2026-02-19T21:28:55","modified_gmt":"2026-02-19T21:28:55","slug":"how-often-may-a-shutdown-happen-due-to-external-disturbances","status":"publish","type":"page","link":"https:\/\/circuitenergy.ca\/staging\/8539\/how-often-may-a-shutdown-happen-due-to-external-disturbances\/","title":{"rendered":"How often may a shutdown happen due to external disturbances?"},"content":{"rendered":"\t\t
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This engineering document from <\/span>Circuit Energy<\/span><\/b> explores the frequency and causes of unexpected facility shutdowns due to external electrical disturbances<\/span><\/span>. <\/span>It highlights how even minor voltage fluctuations, which occur randomly, can significantly impact customer operations<\/span><\/span>.<\/span><\/p>

Frequency of Power Interruptions<\/h3>
  • Global Benchmarks<\/span><\/b>: Reliability performance is often measured by the <\/span>System Average Interruption Frequency Index (SAIFI)<\/span><\/b>, which tracks the number of actual power interruptions lasting more than five minutes that a customer experiences annually<\/span><\/span>.<\/span><\/li>

  • Developed Countries<\/span><\/b>: Average SAIFI levels typically range from <\/span>0.5 to 5.0 interruptions per year<\/span><\/b><\/span>.<\/span><\/p><\/li>

  • United States<\/span><\/b>: The average SAIFI is approximately <\/span>1.3 interruptions per year<\/span><\/b><\/span>.<\/span><\/p><\/li>

  • Influencing Factors<\/span><\/b>: These rates depend on weather conditions, the age and type of infrastructure (underground vs. overhead), and system design (networked vs. radial)<\/span><\/span>.<\/span><\/p>

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    The Impact of Voltage Sags<\/h3>

    While prolonged outages are rare, momentary voltage sags are much more frequent and can be just as disruptive to sensitive equipment<\/span><\/span>.<\/span><\/p>

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    • Definition<\/span><\/b>: Even sags lasting less than 100 ms can shut down susceptible facility operations<\/span><\/span>.<\/span><\/li>
    • Measurement<\/span><\/b>: The <\/span>System Average RMS (Variation) Frequency Index (SARFI)<\/span><\/b> quantifies the average number of voltage sags below a specific threshold (e.g., SARFI70 for sags below 70% of nominal voltage)<\/span><\/span>.<\/span><\/li>

    • Equipment Sensitivity<\/b>:<\/p>

      • In the U.S., sags below <\/span>70%<\/span><\/b> occur roughly <\/span>18 times per year<\/span><\/b><\/span>.<\/span><\/p><\/li>

      • If equipment is sensitive to minor sags of <\/span>90%<\/span><\/b>, the number of disruptive events jumps to about <\/span>50 per year<\/span><\/b><\/span>.<\/span><\/p><\/li><\/ul><\/li><\/ul>

        The document emphasizes that understanding equipment sensitivity is critical for determining the true impact of these disturbances on a facility<\/span><\/span>.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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