Modelling and Evaluating Effect of Automation, Protection, and Control on Reliability of Power Distribution Systems

Abstract: This thesis deals with modeling and evaluating effect ofautomation, protection, and control on reliability of powerdistribution systems. It presents the work and results of theproject ``Impacts of Distribution Automation on SystemReliability'' within the research program ``New DistributionSystems for Power Utilities'' performed at Competence Centre inElectric Power Engineering, KTH.Analysis of the customer failure statistics has shown thatthe distribution systems make the greatest contribution to theunavailability of power supply to customers. To improve thereliability, consideration is being given to increasing thelevel of automation and control. It is desired that thereliability improvement related to the automation and controlcould be quantified. The objective of the work is thus todevelop analytical models, techniques, and computer program inorder to include the effect of automation and control in thereliability assessment of distribution systems.The work is performed in a two-stage approach. In the firststage, the effort is devoted to develop a computer program forthe reliability assessment of distribution systems (RADPOW),and to investigate several issues associated with the remotecontrol and feeder automation. In the second stage, detailedanalytical models and a novel evaluation approach are developedto assess the effect of the secondary systems, includingprotection, computer systems, communication, and local control.Using the developed models and techniques, the automationevaluation continues further in depth during the second stage,and a number of issues related to the distribution automationhave been investigated.The investigations show that the benefit in systemreliability can be increased significantly by automation andremote control. The feeder automation benefits the servicerestoration after the fault has occurred. Generally the benefitin the reliability can be improvedas the reliability ofcontrol system increases, but the degree of this improvement islimited.Keywords:electric distribution system, reliabilityassessment, distribution automation, control, protection,modelling, operation, control system.