In July 2006 the District of Columbia Public Service Commission (PSC) initiated a formal inquiry into the development of uniform interconnection procedures for on-site distributed generation systems. The PSC subsequently concluded that an interconnection standard was feasible and continued with the rule making process, culminating with the adoption of final interconnection regulations in February 2009 (DC PSC Order No. 15182). The rules apply to all distributed generation systems of 10 megawatts (MW) or smaller that are operated in parallel with the electric distribution system and are not subject to the interconnection requirements of the PJM Interconnection.
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, and the type of distribution circuit to which a facility will be connected. The basic definitions* for each level are as follows:
Level 1: Certified, inverter-based systems with a capacity rating of 10 kilowatts (kW) or less.
Level 2: Certified systems with a capacity of 2 MW or less, connected to a radial distribution network or a spot network serving one customer. Area network connections are not permitted under Level 2.
Level 3: Only applies to systems that will not export power to the grid. For area networks (3A), systems must be certified and have a capacity of 50 kW or less; or for radial distribution networks (3B), systems must have a capacity rating of 10 MW or less.
Level 4: Systems with a capacity of 10 MW or less that do not meet the criteria for inclusion in a lower tier, generally including all systems that require additional construction by the utility in order accommodate the facility.
The interconnection regulations generally use IEEE 1547 as a technical standard for evaluation of all levels of interconnection. Systems are considered to be lab-certified if the components have been evaluated by a nationally recognized testing laboratory as compliant with UL 1741 (inverters) and IEEE 1547.1. The rules specify the technical screens which may be applied to applications at each level of review and time limits for different stages of the evaluation process. Generally speaking, higher level applications are subject to more intensive screening and longer time limits.
A lockable external disconnect switch is not required for Level 1 interconnections, but is required for Levels 2 – 4. Facilities larger than 1 MW must carry general liability insurance with coverage of at least $2 million per occurrence and $4 million in aggregate, and the policy must also name the utility as an additional insured party. Standardized interconnection agreements are available for all four levels of review and are available in the February 2009 PSC Notice of Final Rulemaking. The interconnection agreements for all four levels are attached to the final rules. The rules and accompanying standard forms also contain details regarding application fees and avenues for dispute resolution.
The PSC adopted net-metering rules in February 2005 for residential and commercial electric customers with renewable-energy systems, fuel cells, cogeneration and microturbines up to 100 kilowatts (kW) in capacity. In January 2007 the PSC approved a net-metering tariff filed by Pepco -- the only electric distribution company that serves the District -- which also contained certain technical standards for net metered facilities. Prior to this, in 2003, Pepco had filed an interconnection tariff to address larger qualifying facilities (QFs) under PURPA.
*The definitions here cover several important classification criteria; however, interested parties should consult the actual rule for more precise definitions and additional restrictions.