Intelligent Over Current Relays Based on Interval Type 2 Fuzzy Logic Approach Margo Pujiantara Department of Electrical Engineering Institut Teknologi Sepuluh Nopember (ITS) Surabaya, Indonesia E-mail: margo@ee.its.ac.id Muhammad Abdillah Department of Electrical Engineering Institut Teknologi Sepuluh Nopember (ITS) Surabaya, Indonesia E-mail: abdillah@elect-eng.its.ac.id Abstract—This paper proposed a new method for over current relays (OCs) problem calculation. The proposed method for over current relays problems calculation is known as the interval type 2 fuzzy logic (IT2FL). Ip and TMS of over current relays were used as IT2FL input, while the IT2FL output as operating time of over current relays. The aim of IT2FL application use was to determine the accuracy of the over current relays’ operating time because that of the model relay over current (OC) has an important role for efficient coordination of power system protection devices. To evaluate the performance of the proposed method, the method was applied on PT. Kaltim Parna Industri’s (PT.KPI) electrical power system. Since it is a petrochemical industry, its protection system should be excellence for maintaining the system’s reliability. The proposed method was compared to both the fuzzy logic approach and the conventional method. The simulation results indicated that the new model could determine more accurately than the other one. Keywords- over current relays; interval type 2 fuzzy logic; power system protection devices; fuzzy logic I. INTRODUCTION A relay design improvement used on industrial electrical power system is needed due to the addition of an unexpected load on industries which eventually forces the power systems to operate to their limits. The most widely used method for over-current relay problem analysis is the time-current curve of relay method [1]. Recently, digital computers play a very important role in data processing in addition to their role for over-current relay problem analysis, especially, the software for the model of the over-current relay characteristics protection coordination schemes in power systems [2]. A software model can be used not only for the over-current relay representation, but also for other methods like direct data storage techniques. This technique uses the results of different TMS settings calculations stored in a database, then the operating point relay is selected based on the data stored in database systems. When the operating point chosen does not match with one of the values in the database that has been made, the interpolation technique is applied to determine the relay operating time. This technique has a drawback that requires a large database for storing amounts of large data. This paper described the over current problem solving using the interval type 2 fuzzy logic method. This method is expected to replace the conventional one to determine the over current relay operating time. The purpose to conduct this research was to analyze a short circuit protection and to coordinate electrical systems so that it would be easier for users to set up the inverse curve of a relay protection system. The paper is organized as follows. Section II presents a brief discussion on modeling and problem formulation of the system. Section III describes the proposed method. Section IV describes the implementation of the proposed method to the system. Section V discusses the simulation results. Finally, the last section is the conclusions. II. SYSTEM MODELING AND PROBLEM FORMULATION 2.1 System modeling This paper used PT. Kaltim Parna Industri (PT.KPI) electrical power system modeling. PT KPI is a petrochemical industry with production capacity of 1500 MTPD. It will make power sharing with PT. KDM whose composition is 80:20 ratios. The capacities of STG (Steam Turbine Generator) in PT.KPI are 7.5 MVA, 11 kV; pf 0.8; 1500 rpm as operated in normal conditions. Figure 1. Single line diagram of PT.KPI electrical power system 2012 International Conference in Green and Ubiquitous Technology 978-1-4577-2171-7/12/$26.00 ©2011 IEEE