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Interconnection Standards

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In December 2007, the Connecticut Department of Public Utility Control (DPUC) now called the Public Utilities Regulatory Authority (PURA) approved new interconnection guidelines for distributed energy systems up to 20 megawatts (MW) in capacity. Connecticut's interconnection guidelines apply to the state's two investor-owned utilities -- Connecticut Light and Power Company (CL&P) and United Illuminating Company (UI) -- and are modeled on the Federal Energy Regulatory Commission's (FERC) interconnection standards for small generators.*

Connecticut's interconnection guidelines, like FERC's standards, include provisions for three levels of systems:

  • Certified, inverter-based systems no larger than 10 kilowatts (kW) in capacity (application fees: $100);
  • Certified systems no larger than 2 megawatts (MW) in capacity (application fees: $500); and
  • All other systems no larger than 20 MW in capacity. Note that the guidelines include "additional process steps" for generators greater than 5 MW (application fees: $1000, study fees will also apply).

Connecticut's guidelines include a standard interconnection agreement and application fees that vary by system type. However, Connecticut's guidelines are stricter than FERC's standards, differing from the federal standards in several significant ways:

  • Customers are required to install an external disconnect switch and an interconnection transformer.
  • Customers must indemnify their utility against "all causes of action," including personal injury or property damage to third parties.
  • Customers are required to maintain liability insurance in specified amounts based on the system's capacity.
  • In addition, the utilities were required to collaboratively submit to the PURA a status report on the research and development of area network interconnection standards. This report was completed in December 2009, and the PURA has reached a final decision (03-01-15RE02) on the docket. The PURA has determined that the utilities can interconnect inverter-based generators (up to 50 kW) on area networks.

The guidelines address requirements for study fees and include technical screens for each level of interconnection. Utilities and customers must follow general procedural timelines.

For systems 10 kW or less: Interconnections are provided in a first-come, first-serve basis in a non-discriminatory manner. The interconnection requires approval from the Municipal Electrical Inspector and a witness from the utility. After completion of the interconnection request, the utility has 10 business days to respond to the request, or the commissioning test is waived. The interconnection must be in compliance with local, state, federal and utility safety rules including the IEE 1574. The customers are required to maintain a liability insurance of $300,000 per interconnection. Total application fee of $100 is required for the process. The guidelines for interconnection for generation facilities less than 10 kW can be accessed here.

For systems 10kW – 20MW: Interconnection process for systems greater than 10kW varies depending on the generation location, size, and customer requirements. Depending where the customer wants to interconnect, the system could fall under either FERC jurisdiction or State jurisdiction. Generators who want to interconnect to sell electricity the wholesale market fall under FERC jurisdiction and must submit application to ISO NE, while customers under net-metering rules or under DUPC approved tariff are subject to State regulation and must submit application to their utilities. Systems smaller than 2MW with meet provided codes and standards have the option for fast track review process.  All generating facilities are required to maintain general liability insurance that range from $300,000 to $5,000,000 depending on the size. General guideline for interconnection for systems larger than 10kW can be accessed here.

For systems greater than 20 MW:  A standard procedure for interconnection for generation systems greater than 20 MW has not been developed, since large generators rarely interconnect with the utility. However in such case, the utility will use its general guidelines to conduct its review with time frames and feasibility studies adjusted accordance with the ISO NE Tariff, schedule 22. 

* FERC's interconnection standards are applicable to generator interconnections subject to FERC jurisdiction, whereas Connecticut's interconnection guidelines apply to state-jurisdiction interconnections, which typically occur at the distribution level. FERC standards were implemented by ISO-New England (ISO) in ISO Schedule 23, which is applicable to FERC-jurisdictional interconnections.