IEEE sets standard for DG grid connections

John Stevens

Sandia PV projects

Albuquerque, N.M.

An Institute of Electrical and Electronics Engineers (IEEE)-sponsored working group has developed the first interconnection standard of its kind for allowing utility interconnections of non-utility-owned distributed generation (DG) equipment.

Developed to simplify the process of interconnecting photovoltaic (PV) systems with an electric utility, unique aspects of this standard include tightly defined requirements for interconnecting hardware that can be tested by independent test laboratories, such as Underwriters Laboratories-removing former barriers to PV use throughout the country.

John Stevens, Sandia National Laboratories, Albuquerque, N.M., chaired the working group, which included about 25 members representing the utility industry, the PV industry, PV inverter manufacturers and PV researchers. IEEE Std 929-2000, known informally as IEEE 929, provides a standard that PV interconnection hardware can be designed to, thus removing the requirement for specialized hardware for different utility jurisdictions. It includes specific requirements for systems up to 10 kW, but covers systems of all sizes. The standard actually applies to the PV inverter, the device that converts the PV dc energy into utility-compatible ac energy. Similar inverters are used in other DG systems such as fuel cells and microturbines. Many of the requirements for interconnection that are described in IEEE 929 might also be adopted for these other technologies.

IEEE 929 provides guidance for operating voltage and frequency windows, trip times for excursions outside these windows, requirements for waveform distortion, as well as defining a non-islanding inverter. An important parallel effort was performed at Underwriters Laboratories where a test procedure, UL 1741, was written for use in verifying an inverter meets IEEE 929 requirements.

For additional information about IEEE 929, contact John Stevens, Sandia PV projects, at 505-844-3698 or e-mail at jwsteve@sandia.gov.

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