TABLE OF CONTENTS This chapter addresses the issues relating to the reliability assessment of distribution systems in which local generation is embedded. Superficially it could be expected that conventional approaches used for existing systems would suffice. However, this would be an erroneous conclusion for reasons discussed later in this chapter, although the required techniques can be based on developments of existing approaches. To appreciate all the issues involved it is therefore desirable to review existing approaches and their limitations regarding embedded generation before developing approaches and techniques to deal with these systems.
Reliability has always been an important system issue and it has been incumbent on power system managers, designers, planners and operators to ensure that customers receive adequate and secure supplies within reasonable economic constraints. Historically, this has been assessed using deterministic criteria, techniques and indices. As an example, the UK criteria centre on the application of Engineering Recommendation P2/5 [1]. This sets restoration requirements depending on the maximum demand of the load group being considered. In addition, the UK regional electricity companies (RECs) are expected to conform to sets of Guaranteed Standards [2] of service with penalty payments having to be made if these are violated. One Guaranteed Standard is service must now be restored within 18 h. Similar penalty payments are made in other countries such as Norway. The introduction of penalty payments indicates that economic methods for reducing the number of violations are very worthy of consideration.
As a concept, reliability is an inherent characteristic and a...
