In September 2007, the Washington Utilities and Transportation Commission (UTC) adopted interconnection standards for distributed generation (DG) systems up to 20 megawatts (MW) in capacity. The revised standards provide for two separate levels of interconnection based on system capacity. The first level applies to systems up to 300 kilowatts (kW). The second level, which applies to systems sized between 300 kW and 20 MW, embraces the Federal Energy Regulatory Commission's (FERC) interconnection standards.* The UTC's standards apply to the state's investor-owned electric utilities -- but not to municipal utilities or electric cooperatives.
All interconnections of systems up to 300 kW must conform to all applicable codes and standards for safe and reliable operation, including the National Electric Code (NEC); National Electric Safety Code (NESC); the standards of the Institute of Electrical and Electronics Engineers (IEEE); the standards of the North American Electric Reliability Corporation (NERC); the standards of the Western Electricity Coordinating Council (WECC); American National Standards Institute (ANSI); Underwriters Laboratories (UL) standards; local, state and federal building codes, and any electrical company's written electric service requirement approved by the UTC.
With utility approval, interconnection to spot networks and area networks is permitted for systems up to 300 kW. A UL-approved safety disconnect switch is generally required. However, this requirement may be waived if a customer (1) demonstrates, to the satisfaction of utility, that a system will perform physical disconnection of the generating equipment supply internally, and (2) agrees that service may be disconnected entirely if the system must be physically disconnected for any reason. Utilities have the authority to review the need for a dedicated distribution transformer. If such equipment is necessary, the customer must pay for the costs. Systems eligible for net metering do not require additional liability insurance. However, utilities are authorized to require additional insurance and indemnification for systems ineligible for net metering (but not greater than 300 kW).
Utilities must have a designated point of contact for customers seeking to interconnect systems up to 300 kW, and must file with the UTC a standard form application and a model interconnection agreement. Application fees are limited to $100 for systems up to 25 kW, and $500 for systems greater than 25 kW but not greater than 300 kW. The UTC's rules include provisions for dispute resolution.
For systems sized 300 kW to 20 MW, utilities must offer service equivalent in all procedural and technical respects to the interconnection service the utility offers under the small generator interconnection provisions of its open access transmission tariff (OATT) as approved by the FERC. The FERC's standards for systems up to 20 MW provide for three levels of interconnection. (However, the first level -- the 10-kW inverter process -- does not apply in Washington, because these smaller systems are covered by the rules described above.) The UTC could approve an alternative proposal if a utility demonstrates that the FERC's interconnection standards will impair service adequacy, reliability or safety, or will otherwise be incompatible with the utility's electric system.
''* In general, the FERC's interconnection standards for DG systems up to 20 MW apply to facilities that connect at the transmission level. State-level interconnection standards generally govern interconnection at the distribution level.''