Numerous studies conducted during the past 25 years have all identified transient activity as the most common AC power anomaly likely to disrupt or damage critical electronic loads. 

G.W ALLEN and D. Segall of IBM System Development Division conducted one of the most respected studies. They monitored AC power at 200 locations, where IBM equipment was installed and operating, in 25 cities across the United States. They recorded the number of various AC power anomalies that disrupted equipment operation during a two-year time span.

The Allen-Segall study concludes that that 88.5% of AC power problems are transient related.

Allen and Segall found that the most disruptive power problem regard Oscillatory, decaying transients that occurred 62.6 times monthly and represents 49% of the total number of AC power abnormalities. These are examples of long duration, non-lightning related, transients.

Lightning induced voltage spikes or impulse transients occurred 50.7 times a month, representing 39.5% of the total number of AC power hits.

In contrast, power outages accounted for only .5% of equipment disruptions while sags and swells were responsible for 11% of AC power problems.

Electrical distribution systems have not changed significantly from the mid-seventies while electrical and electronic equipment has become much more sophisticated. Now, power outages are becoming more infrequent while harmonic distortion has become a major concern for equipment users. Transient activity has also become increasingly more threatening to modern state of the art electrical and electronic load devices

Stedi-Power, Inc
5044 B U Bowman Drive #102
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Last Updated: 07 Jun 2004
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