Utility Group Backs New Power-Quality Metrics

The Electric Power Research Institute (EPRI), the research arm of the investor-owned utility industry, is backing the recommendations of an affiliated technology group to change how power quality and reliability are described. The new metrics differentiate between needs of various analog and digital systems, allowing greater customization of electrical-system design.

Current specifications often focus simply on total power availability. This approach ignores the fact that, in some settings, a single 30-second outage could have the same financial consequences as a number of five-minute outages in less sensitive environments. A recent report authored by the Consortium for Electric Infrastructure to Support a Digital Society (CEIDS) suggests a more tiered approach to describing power-quality needs and performance.

At the highest level (Level 1), a failure is described as any voltage falling below 70% of nominal, as defined by the Information Technology Industry Council’s ITIC curve, for more than 0.02 seconds, or below 80% of nominal for more than 0.05 seconds. At the lowest level (Level 4), a failure is described as an interruption lasting at least five minutes.

The application of this stepped methodology means that systems serving sensitive applications can be specified as requiring, for example, a minimum time between failure of at least one year at Level 1 standards. CEIDS is sponsored by EPRI, along with EPRI’s associated technology division, the Electricity Innovation Institute.

From Pure Power, Spring 2003

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