Interconnection of Distributed Generation Facilities (up to 10 MW)
The interconnection rules set four levels of review for interconnection requests. A project must meet all of the requirements of a given classification in order to be eligible for that level of expedited review. The level of review required is generally based on system capacity, whether system components are certified by a nationally recognized testing laboratory (NRTL), and whether the system is connected to a radial distribution circuit or to an area network. The basic definitions* for each tier are as follows:
- Tier 1: Certified, inverter-based systems with a capacity rating of 10 kilowatts (kW) or less.
- Tier 2: Certified systems with a capacity rating of 2 MW or less, connected to a radial distribution network or a spot network serving one customer.
- Tier 3: Certified systems with a capacity rating of 50 kW or less connected to an area network and from which power will not be exported; or certified, non-power-exporting systems with a capacity rating of 10 MW or less connected to a radial distribution network.
- Tier 4: Systems with a capacity of 10 MW or less that do not meet the criteria for inclusion in a lower tier, including all systems using non-certified components and those that require additional construction by the utility in order accommodate the facility.
The ICC adopted IEEE 1547 as the technical standard of evaluation in July 2007. Systems are considered to be lab-certified if the components have been evaluated as compliant with UL 1741 and the 2008 National Electric Code (NEC) according to the testing protocols of IEEE 1547. The rules also specify the technical screens which may be applied to applications at each level of review as well as time limits for different stages of the evaluation process. Generally speaking, higher level applications are subject to more intensive screening and longer time limits.
All systems are required to have an external disconnect switch directly accessible to the utility. Facilities larger than 1 MW must carry liability insurance with coverage of at least $2 million per occurrence and $4 million in aggregate. Standardized interconnection agreements are available for all four tiers. The Tier 1 agreement is a simplified version of that used for projects requiring higher levels of review.
Interconnection of Large Distributed Generation Facilities (10 MW or larger)
The ICC adopted a separate set of rules applicable to distributed generation facilities over 10 Megawatts, which are not covered under the above interconnection standards. These rules provide a standard set of procedures covering the interconnection process as well as standard agreements. It should be noted that interconnections covered by the Federal Energy Regulatory Commission (FERC), the Midwest Independent Transmission System Operator, or PJM Interconnection are not subject to these new rules. See ICC Docket 08-0481 for more information.
* The definitions here cover several important classification criteria; however, interested parties should consult the actual rule for more precise definitions and additional restrictions.