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Utility-Interconnected Photovoltaic Systems: Evaluating the Rationale for the Utility-Accessible External Disconnect Switch
M.H. Coddington, R.M. Margolis, and J. Aabakken

The utility-accessible alternating current (AC) external disconnect switch (EDS) for distributed generators, including photovoltaic (PV) systems, is a hardware feature that allows a utility’s employees to manually disconnect a customer-owned generator from the electricity grid. Proponents of the EDS contend that it is necessary to keep utility line workers safe when they make repairs to the electric distribution system. Opponents assert it is a redundant feature that adds cost without providing tangible benefits.
In this paper, the authors examined the utility-accessible EDS debate in the context of utility-interactive PV systems for residential and small commercial installations. They also evaluated the rationale for EDS requirements. In particular, they were focusing on the safety, reliability, and cost implications of the EDS. They observed that in a number of states in which public utility commissions (PUCs) and utilities had gained experience with PV systems, they have decided to eliminate the EDS requirement. These decisions typically require that utility-interactive PV systems use inverters that meet relevant Underwriters Laboratories (UL) and Institute of Electrical and Electronics Engineers (IEEE) standards.

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