By Steve Conover
In recent years, there has been an unprecedented focus on grid-tied renewable energy systems and other distributed generation (DG). With ever-growing concerns about the conservation of natural resources, pollution, dependence on foreign oil, and other challenges, we have witnessed a worldwide interest in the development and proliferation of grid-tied DG applications.
In many countries around the globe, including the United States, the tremendous growth in renewable energy solutions, such as wind and solar photovoltaic (PV) systems, signifies an ongoing shift in the composition of our electricity supply – a trend that is expected to continue its growth in the foreseeable future, fueled by innovative initiatives such as TVA’s recent Renewable Standby Offer (RSO) and Solar Solutions Initiative (SSI) programs. Recently, the Rural Utility Service (RUS) held hearings to gather public comments on advancing renewable energy and project financing programs for a direct loan program. While it is too early to know the full impact this will have with RUS borrowers, it serves as another sign of our government’s interest in distributed generation and renewable energy.
As more and more grid tied DG systems are installed, the complexity of evaluating potential impacts to the electric system increases. It is vital that power distributors understand and consider the impacts that such installations can have. Tying DG systems to the electric grid often poses a plethora of challenges, which can seem daunting to power distributors. Even with almost universally recognized standards such as IEEE 1547 and UL 1741, there are many instances where decisions must be made on a case-by-case basis in order to effectively evaluate and assure that DG systems will perform to expectations and operate safely and effectively.
IEEE 1547 is a grid-tied DG standard that covers the majority of DGs installed in the United States. It is a performance standard stipulating the conditions that must be met, but it does not define exactly how DG systems must comply. Also, there are sometimes steps that electric utilities must take in order to help assure that DGs will function properly in specific circumstances. For instance, some alterations to the settings of electronically controlled sectionalizing devices might be necessary, requiring close coordination between the DG installer and the utility.
System Impact Studies, which evaluate the effects of proposed DGs on electric distribution systems, are frequently necessary and highly recommended. These studies not only identify potential problems, but also provide recommendations on specific steps that should be taken to overcome them. P&D continues to be actively involved with clients performing system impact studies and assisting with other tasks associated with DG integration. If your utility needs assistance, please contact us.