A Decision Analysis Model to Determine the Appropriate Level of Protection for the Small Power Producer/Utility Interconnection

This paper formulates a methodology to aid in deciding on the appropriate quality and quantity of protection equipment required for a small electric power producing device, known in the industry as dispersed storage and generation (DSG). In this methodology, a discrete state-space model of the response of both the utility´s and DSG´s protection equipment to shunt and series faults on an electric distribution feeder is developed. The parameters of the model are linked to the component reliabilities of the protection schemes and the specific characteristics of the distribution system. The mathematics of semi-Markov theory are used in the methodology to calculate the expected annual damage costs for various protection schemes. The total costs are calculated for alternative protection schemes by considering equipment damaqe, repair time, lost revenue, outage costs, and time spent in different operating states during the hazardous conditions. This methodology is useful to electric utilities, small power producers, and regulatory bodies who must make decisions regarding the adequacy as well as the cost-effectiveness of protection requirements for DSG installations.