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ITIC (CBEMA) curve checker

Enter a voltage and a duration and see where the disturbance falls on the ITIC (CBEMA) curve and SEMI F47, with its IEEE 1159 category. Free, in your browser.

ITIC (CBEMA)Below the lower edge65.0% for 100.0 ms · edge at this duration: 70% · margin -5.0 points
SEMI F47Within the ride-through curveride-through required at this duration: 50%
IEEE 1159 categoryInstantaneous sag (0.5–30 cycles, 0.1–0.9 pu).by magnitude and duration at 50 Hz
1 ms10 ms20 ms100 ms0.5 s1 s10 s100 s020406080100120140160180200duration (log scale)% of nominal voltageITIC no-interruption regionSEMI F47

How to read the result

  • Voltage is the retained RMS voltage as a percentage of nominal: the lowest value for a sag, the highest for a swell. A sag “to 65%” is entered as 65.
  • Duration is how long the voltage stayed outside the 90–110% band.
  • Margin is the distance, in percentage points, to the nearer edge of the ITIC envelope: positive inside, negative outside.

A point outside the envelope says the disturbance was more severe than typical IT equipment is designed for. It does not say that a particular piece of equipment tripped, and a point inside does not say that everything rode through. See the ITIC (CBEMA) curve and SEMI F47, point by point.

Have the record instead?

Drop the COMTRADE record into SagSwell and every sag, swell and interruption in it is measured and placed on this curve for you, per phase, with SEMI F47 as an overlay. Free, with nothing to install. No file to hand? Try one of the sample COMTRADE files.