Federal Interconnection Standards: Putting DG in a Box
Technology Collaborative benefited from the efforts already undertaken in other states as well as national groups responsible for creating industry standards. The Institute of Electric and Electronic Engineers (IEEE) and the Underwriters Laboratories (UL) recently developed standards for DG interconnections. The UL standard (UL 1741) offers certified design standards for inverter-based DGs under 10 kW, common ratings for commercially available PV systems. The IEEE standard (P1547) establishes minimum technical and performance standards for interconnecting DG up to 10 MW.
Developing these standards takes time and money. The IEEE standard P1547 crosses a major threshold, since it took just three years for approval versus five to10 years for many IEEE standards. Undoubtedly this accelerated timeline would not have been possible without the support from the Department of Energy's Distributed Energy and Electricity Reliability (DEER) Program, which in addition to IEEE 1547, also helped NARUC develop its interconnection model and the Public Utility Commission of Texas write its Interconnection Guidebook. Patricia Hoffman, the DEER acting program manager, says, "We recognized early on that if these technologies, which are so critical to the future of our energy infrastructure, were going to survive we needed to have national interconnection standards."
IEEE 1547 has not yet addressed the thorny problem of integrating DG into low voltage (secondary) grid network systems used in downtown districts in most major cities. Utilities have been exceedingly cautious on DG network integration so as not to jeopardize reliability or power quality on these highly complex grids. IEEE is now developing application guidelines that eventually may address network systems (the IEEE standard includes less complex spot networks). However, compliance is voluntary under either standard and IEEE 1547's broad language requires interpretation if it is to be used as a comprehensive interconnection standard. IEEE 1547 also does not include process or commercial issues such as applications, timelines and agreements. Scott A. Castelaz, vice president for corporate development and external affairs at ENCORP (a leading provider of DG solutions), says, "The recently passed IEEE standards are an important step in the right direction. However, the adoption of these standards should be viewed as a journey and not so much as a destination. In many important aspects the non-technical factors are in much need of improvement relating to tariffs, contracts, and the general process to obtain a safe, reliable interconnection. This will not only improve the existing market base for interconnection but will also spur new demand for the DG market itself."
Is a Hybrid Arrangement the Answer?
Questions arise on two fronts regarding interconnection standards for small DG (less than 20 MW): Should states be solely responsible for interconnection standards for small DG? And, are FERC's proposed standards relevant for the majority of small DG interconnecting at distribution voltages?
DG installations that include third-party export sales presumably would fall under FERC's jurisdiction, regardless of voltage. Notably, the majority of applications for interconnection in California are small without exports to the grid, thereby avoiding the regulatory burden associated with third-party sales. As demonstrated in Figure 1, which is based on a hypothetical population of 1,000 applications,