Engineering and Technology Journal e-ISSN: 2456-3358 Volume 07 Issue 10 October-2022, Page No.-1569-1575 DOI: 10.47191/etj/v7i10.04, I.F. – 6.484 © 2022, ETJ 1569 Paulus Mangera 1 , ETJ Volume 7 Issue 10 October 2022 Reliability Analysis of 20 kV Medium Voltage Air Line Distribution System at Semangga Switch Substation in Merauke Regency Paulus Mangera 1 , Damis Hardiantono 2 , Daniel Parenden 3 1,2,3 Musamus University Merauke – Indonesia ABSTRACT: The breakdown of electrical energy can be caused by the unwanted failures that occur in the electric power system, especially in the distribution system, and have an impact on service continuity which can be a permanent failure, temporary failure, three phase short circuit failure, double phase short circuit failure, and black out. To anticipate this, a study needs to be done to analyze and find out how well the distribution system reliability index. Determination of the analysis was done by the method of data retrieval related to the analysis variable. Besides, in determining the results of the analysis, calculations using System Average Interruption Frequency Index (SAIFI), Customer Interruption Frequency Index (CAIFI), System Average Interruption Duration Index (SAIDI) and Customer Average Interruption Duration Index (CAIDI) analyses were performed. Based on the reliability of the distribution network, the SAIFI and CAIDI maximum threshold value setup by PT. PLN (The National Electricity Company) at the Semangga substation each worth 3.00 failures/customer.year and 3.00 failures/customerr while SAIDI and CAIDI each worth value of 3.40 hours/customer.year and 3.40 hours/customer.failure. All feeders installed at Semangga switch substation in realization gives reliability indices smaller than the target that has been set., it is mean that 20 kV medium voltage air line distribution system at Semangga switch substation still reliable and the duration of the failure time for each feeder was an average of 3 minutes of each failure and the number of failures every month was an average of 15 times of each feeder. KEYWORDS: substation, reliability, SAIFI, SAIDI, CAFI, CAIDI, distribution system 1. INTRODUCTION The quality of reliability of electrical energy services can be seen from the length of outages and how often blackouts occur in a certain period of time [1]. Reliability indices is a measure of reliability expressed in probability quantities [2]. Failures that occur in the distribution network will cause disruption of service continuity. This failure can be a permanent failure, temporary failure, three phase short circuit failure, double phase short circuit failure, and black out [3][4]. Reliability indices basically is a number or parameter that indicates the level of service or the level of reliability of electricity supply to consumers. The parameters of performance in electricity especially distribution system namely: SAIFI, CAIFI, SAIDI and CAIDI and the steps used were interviews and data retrieval of failures [5]. By calculated these parameters, it will be known how many indices are produced whether it is in accordance with the standards set by the National Electricity Company specially in the region of Merauke as shown in figure 1 [1], to be followed up so that in the future services in the distribution of electricity to customers do not experience many obstacles [6]. Therefore, a blackout analysis is needed in order to reduce the high level of blackouts so as to improve the quality of electricity and customer service [7]. There are several factors that must be known and calculated before carrying out an analysis of the reliability of the electrical distribution system, among others: the frequency of failure and duration / duration of failure, which comes from the failure of distribution network equipment or failure at its load point [8]. In this paper, it is proposed to determine the value of reliability and various indices related to the quality of service to customers. But this study decribed here focuses on three feeders that power electrical supplied by Semangga Switch Substation, namely: Kurik feeder, Tanah Miring feeder and Sidomulyo feeder by using the mathematical analysis by using equations theoritically. The problems in the calculation are [9]: 1. Determine the reliability indices of SAIDI, SAIFI and CAIDI, based on the failure rate and duration of outages experienced by customers. 2. Comparison of the calculated values with the threshold values applied at Semangga Switch Substation. 2. MATERIAL AND METHOD 2.1 Reliability Indices This indices can then be combined with the customer composition in the distribution system to evaluate the system indices. In the distribution area, the usual indices are the load point failure rate (or frequency), the average outage duration, and the average annual outage time. Normal utility practise is