Manage power, shield processes, save money (sidebar)

March 1, 2004
What is a power sag or dip?

According to the Electric Power Research Institute (EPRI) Power Electronics Applications Center, “A sag or dip, as defined by IEEE (Institute of Electrical and Electronics Engineers) Standard 1159-1995, ‘IEEE Recommended Practice for Monitoring Electric Power Quality,’ is a decrease in rms (root-mean-square) voltage or current at the power frequency for durations from 0.5 cycles to 1 minute, reported as the remaining voltage . . .

“Terminology used to describe the magnitude of a voltage sag (or short-duration voltage decrease) is confusing. The recommended usage is ‘a sag to 20 percent,’ which means that the line voltage is reduced down to 20 percent of the normal value, not reduced by 20 percent . . . The IEC (International Electrotechnical Commission) definition for this phenomenon is dip. The two terms are considered interchangeable, with sag being preferred in the United States . . .

“Typical sag durations defined in some publications range from two milliseconds (about one-eighth of a cycle) to a couple of minutes. Sag durations are subdivided here into three categories—instantaneous, momentary and temporary—coinciding with the three categories of interruptions and swells.”

See the story that goes with this sidebar: Manage power, shield processes, save money

Sponsored Recommendations

Why Go Beyond Traditional HMI/SCADA

Traditional HMI/SCADAs are being reinvented with today's growing dependence on mobile technology. Discover how AVEVA is implementing this software into your everyday devices to...

4 Reasons to move to a subscription model for your HMI/SCADA

Software-as-a-service (SaaS) gives you the technical and financial ability to respond to the changing market and provides efficient control across your entire enterprise—not just...

Is your HMI stuck in the stone age?

What happens when you adopt modern HMI solutions? Learn more about the future of operations control with these six modern HMI must-haves to help you turbocharge operator efficiency...

AVEVA™ System Platform: Smarter, Faster Operations for Enhanced Industrial Performance

AVEVA System Platform (formerly Wonderware) delivers a responsive, modern operations visualization framework designed to enhance performance across all devices with context-aware...