Simulation and Performance Analysis of Resistive Superconductor Surge Current Protection Enemuoh F. O. Department Of Electrical Engineering Nnamdi Azikiwe University, Awka Anambra State, Nigerian Makinde K. Department Of Electrical Engineering Federal Polytechnic, Bida, Niger State, Nigerian Abstract - Increase in power generation capacity of electrical power systems has lead to increase in the fault current level which can exceed the maximum designed short-circuit ratings of the switchgear. Many conventional protective devices like circuit breakers have been installed for protection of excessive fault current in electric power systems required to be tripped by over-current protection relay. In this paper, the simulation modelling and performance analysis of superconductor surge current protection is carried out. The modelling was carried out using Power System Analysis Toolbox while the simulation used matlab codes. The result showed that with the system faulted without the introduction of superconductor surge current protection the fault current was very high. The introduction of superconductor in the power system showed tremendous reduction in the fault current. Keywords: Circuit breaker, Fault current, Simulation, Resistive Superconductor Fault Current Limiters (RSFCL). I. INTRODUCTION problems especially transient stability. Hence, transient stability enhancement of a power system in the event of a short circuit will be of great importance. Employing Fault Current Limiters (FCL) is one of the useful methods to improve the transient stability of a power system. Fault Current Limiter (FCL) especially its resistive type, i.e. Resistive Fault Current Limiter reduces the fault current level of power systems [1]. Limiting current allows the nominal and fault level ratings of equipment, such as converter switching devices or CBs, to be lower than without the SFCL. Current limiting may also limit the actual current density flowing through cables and other equipments, reducing the likelihood of approaching the critical current density of equipment. A properly designed FCL will have large impedance in fault conditions, quick appearance of impedance when fault occurs, provide rapid detection and initiation of limiting action within less than one cycle or 16ms and be capable of addressing two faults within a period of 15 seconds. As a result of the reduction in fault current, the rating of the circuit breaker will be reduced as well as the weight and physical size of the CB. Using SFCLs with CBs may also increase the reliability of successful fault interruption because the SFCL, when operating as designed, will limit the fault current seen by the CB to its rated value [2]. Among the parameters of the FCL, the magnitude of the limiting impedance and its merits affects the current- limiting performance of the FCL much more than the other parameters. In other words, depending upon the kind of the FCL and its merits, the insertion of the FCL in to the power system can result in more severe interrupting problems. Therefore, it is important to study the interrupting behavior of circuit breakers in the presence of the kinds of FCLs. FCLs have large impedance in fault conditions and have very low impedance in normal conditions and also instantaneous recovery to zero impedance post fault clearance [3]. Most importantly, usage of FCLs is to reduce the fault current to withstanding level of existing circuit breakers. So, the existing equipments can still be used to protect the power system. Also after being limited by the FCL, the current is interrupted at its current zero by a circuit breaker. After the interruption of the fault current, a transient recovery voltage (TRV) appears across the contacts of the circuit breaker. To perform a successful interruption, the circuit breaker must withstand the TRV without re- establishment of the arc between the contacts [4]. II. SIMULATION OF THE NINE BUS SYSTEM WITH FAULT The popular Western System Coordinated Council (WSCC) 3 machine, 9-bus system shown in Fig2.1 has been considered to be used for the modeling. In order to see the operation of power system circuits, two cases are considered. (1) Fault condition and (2) When a current limiter is inserted at the point of fault in series. Matlab simulation is used with NR and GS method of iterations and this Matlab simulation is programmed to plot the graphs for each of these conditions with a PSAT simulator. International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 www.ijert.org IJERTV4IS120424 (This work is licensed under a Creative Commons Attribution 4.0 International License.) Vol. 4 Issue 12, December-2015 475