Research to Aid Design and Adoption of Distributed Generation

Distributed generation (DG) is becoming increasingly popular with facilities seeking to boost their power capacity and protect themselves from grid-related power-quality issues. But some critics argue that generators, fuel cells, micro-turbines and other DG applications are not yet plug-and-play solutions. Establishing interconnections with local utility lines and existing facility power systems that are both reliable and safe can still be problematic. Research at the Electric Power Research Institute (EPRI) is seeking to address this issue, focusing on equipment certification standards, interconnection protocols and testing of a proposed Institute of Electrical and Electronics Engineers (IEEE) standard.

One project now being planned is a pilot test of the first certification program directed toward DG equipment. This effort will put a range of products, including microturbines and fuel cells, through a proposed certification process, and will include the development of testing protocols to establish requirements necessary to prove grid compatibility.

Voluntary consensus standards already exist among many manufacturers today. This program is intended to prove the validity of these standards and to establish a more formal certification process to be applied as more equipment makers enter the field. Testing is intended to evaluate a product’s ability to withstand extreme operating environments—in other words, its “immunity”—without exhibiting behaviors, or “emissions,” that might disrupt other connected equipment or the grid. Once testing procedures have been established, researchers will develop a process for accrediting other laboratories’ certification efforts.

A second area of research is planned to investigate the effects of connecting multiple DG devices in close proximity with one another. Although IEEE is developing equipment standards, researchers want to ensure these guidelines are sufficient as more devices are connected both within facilities and to the general grid. A decade ago, many users—and their connected electrical systems—faced problems when first incorporating such nonlinear devices as adjustable-speed drives and induction furnaces. This research is hoped to avoid similar havoc as DG equipment grows in popularity.

In a related effort, researchers will be investigating one particular hazard DG adopters can face. “Islanding” occurs when one or more pieces of DG equipment become isolated from a power system and continue to serve loads independent of the utility system. Such conditions can result in system and equipment damage, and severe injuries. Though commonly accepted methods for preventing islanding exist, researchers want to ensure these are adequate to current needs, especially in fault-clearing and reclosing scenarios.

Finally, a program is underway testing the validity of IEEE’s proposed standard P1547, a universal standard for grid interconnection. Researchers are applying the standard to a range of DG resources and manufacturer-supplied interconnection equipment to ensure the new guidelines adequately address potential installation issues.

From Pure Power, Winter 2002

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