Measurement Practices for Reliability and Power Quality

Abstract

This report provides a distribution reliability measurement ''toolkit'' that is intended to be an asset to regulators, utilities and power users. The metrics and standards discussed range from simple reliability, to power quality, to the new blend of reliability and power quality analysis that is now developing. This report was sponsored by the Office of Electric Transmission and Distribution, U.S. Department of Energy (DOE). Inconsistencies presently exist in commonly agreed-upon practices for measuring the reliability of the distribution systems. However, efforts are being made by a number of organizations to develop solutions. In addition, there is growing interest in methods or standards for measuring power quality, and in defining power quality levels that are acceptable to various industries or user groups. The problems and solutions vary widely among geographic areas and among large investor-owned utilities, rural cooperatives, and municipal utilities; but there is still a great degree of commonality. Industry organizations such as the National Rural Electric Cooperative Association (NRECA), the Electric Power Research Institute (EPRI), the American Public Power Association (APPA), and the Institute of Electrical and Electronics Engineers (IEEE) have made tremendous strides in preparing self-assessment templates, optimization guides, diagnostic techniques, and better definitions of reliability and power quality measures. In addition, public utility commissions have developed codes and methods for assessing performance that consider local needs. There is considerable overlap among these various organizations, and we see real opportunity and value in sharing these methods, guides, and standards in this report. This report provides a ''toolkit'' containing synopses of noteworthy reliability measurement practices. The toolkit has been developed to address the interests of three groups: electric power users, utilities, and regulators. The report will also serve to support activities to develop and share information among industry and regulatory participants about critical resources and practices. The toolkit has been developed by investigating the status of indices and definitions, surveying utility organizations on information sharing, and preparing summaries of reliability standards and monitoring requirements--the issues, needs, work under way, existing standards, practices and guidelines--for the following three classifications: (1) terms and definitions of reliability; (2) power quality standards, guidelines, and measurements; and (3) activities and organizations developing and sharing information on distribution reliability. As these synopses of reliability measurement practices are provided, it must be noted that an economic penalty may be associated with requiring too high a reliability level from the distribution system for all customers. It may be appropriate for the distribution system to supply only some base, generally accepted level of reliability. This base level would be adequate for the majority of customers. Users who need a higher level may find it economical to supply using distributed energy resources (DER) and other local solutions to reliability and power quality needs. Local solutions implemented by the customer may be the most cost-effective method for addressing the more stringent needs of a digital economy. These local solutions include energy storage, small distributed generators, and microgrids. This report also considers the market's role in addressing reliability issues and requirements. The customer's needs are discussed in view of issues such as power quality requirements of digital electronic equipment, the cost of outages, the cost of storage and new infrastructure, and natural gas prices. The market role in addressing these issues and requirements is explored. The economic considerations associated with the reliability issues are discussed, as well as the levels at which these economic decisions could be made. Finally, a discussion is provided of the role DER could play in addressing reliability needs, and the possible role of the market in providing needed levels of reliability.