Impact of Automatic Circuit Reclosers and Distributed Generators on the Reliability Indices of Electrical Distribution Systems

Abstract

Reliability is the ability of power system to perform its intended function as at when due. Parameters used to assess the level at which this is done are called reliability indices. Previous researches have not focused deeply on the effect of installing automatic circuit reclosers ACRs and distributed generators (DGs) on the assessment of reliability indices of electrical power distribution system, hence, the drive towards this research paper. Monte Carlo Simulation (MCS) was performed in MATLAB on the IEEE 34 test feeder. Under three different case studies- when one ACF was installed on the test system, when two ACRs were installed on the test system and when 1MW DG unit was installed on the test system.  Real system data were used as input parameters for the simulation. The overall distribution system reliability was evaluated using the load point and the system reliability indices such as System Average Interruption Frequency Index (SAIFI), System Average Interruption Duration Index (SAIDI) and Customer Average Interruption Duration Index (CAIDI).  (CAIDI), Average Service Availability Index (ASAI) and EUE.The results obtained with the MCS were compared with the results obtained previously for the same test system using analytical approach and was found to be in agreement. The results of the research paper showed that the installation of an automatic circuit recloser gave a reduction in SAIFI value from 17.33hours/year to 14.93 hours/year with the installation of ACR between nodes (800-802). The best improvement was noticed when ACR was installed between nodes (834-842) in the electrical feeder. The value of SAIDI obtained also decreased from 8.90hom/year to 7.99 hours/year with the installation ACR between nodes (800-802). When two ACR were installed in the test system between nodes (828-824) and (824-826), the values obtained for SAIFI were 10.74 hours/year and 11.20 hours/year respectively representing a level of improvement in the SAIFI index. Between these nodes, values of SAIFI were also 4.211 hours/year and 4.423 hours/year which also represents an improvement in SAIDI values.Installation of 1MW Distributed generator (DG) unit in the test system gave SAIFI and SAIDI values of 14.23 hours/year and 5.80 hours/year respectively representing an improvement in there two indices compared to when ACRs were installed at anywhere in the test system. The values obtained for ASAI for different locations of the 1MW DG unit fluctuate throughout the case descriptions. With the installation of the 1MW DG unit between nodes 834-842, 844-846, 834-860, 836-840, and 862-838, the values obtained for ASAI were 5.196, 5.101, 5.012, 6.141 and 6.128 respectively which represent appreciable level of improvement as compared to the base case. With the installation of one DG in the test system, the value obtained for the EUE was 17709kw. With the additional installation of ACR between nodes (846-848), (862-832), (888-890) and (854-856), the values obtained for EUE were 1152 kW, 11926 kW, 13146  kW and 14191 kW respectively indicating a level of reductions in the values of EUE. The ACRs, once installed optimally on the test system improves the reliability of the distribution system by isolating the healthy parts of the system automatically, which maintains the service to a substantial number of customers and reduce the repair time. The integration of DGs into the distribution test system provides the opportunity of operating the distribution system as a microgrid, allowing continuity of service in the network. It also forms a useful basis for evaluating the reliability of distribution feeders.

Keywords: Automate circuit reclosers (ACRs), Distributed generators (DG), Reliability indices, Monte Carlo Simulation Power Distribution systems, SAIFI, SAIDI, CAIDI, ASAI.