Enhancement of Multi-Machine Power System Performance Using Resistive Superconducting Fault Current Limiter

Topics: Electrical engineering, Electric power transmission, Electrical resistance Pages: 11 (2939 words) Published: February 27, 2012
Enhancement of Multi-machine Power System Performance Using Resistive Superconducting Fault Current Limiter

Dr. M. M. A. Mohamed 1, a and Eng. M. A. Gaafar 1, b

1Electrical Engineering Department, Faculty of Engineering, South Valley University, Aswan, Egypt

aemail: mmam72@yahoo.com and bemail: m.a.gafaar@gmail.com

Abstract- One of the worst types of fault that a power system should be designed to withstand is a short circuit. Within the various types of fault current limiters, the superconducting fault current limiter (SCFCL) has an extremely fast current limitation. The rapid switching action and the self-sensing nature of the superconductor make SCFCLs particularly attractive in fault protection. This very fast time response is potentially shorter than those of the classical current limiters. This paper presents a study to the impact of installing resistive type superconducting fault current limiter (RSCFCL) in multi-machine power system during a large disturbance. The system performance without and with RSCFCL is studied. Mainly, three features for RSCFCL are discussed, current limiting capability, voltage drop suppression, and transient stability enhancement. A simple 9-bus 3-machine system is used to explain these features. MATLAB, SIMULINK, and SIMPOWERSYSTEMS software are applied to investigate these features.

Index Terms- Fault current limiter, superconductor, and power system stability.


Increasing power demands are leading to power transmission systems which cover large distances and carry high power. This expansion in power system capacities led to development of large scale generating units and interconnection between networks. Therefore, a fault on the power system may abnormally induce large fault current and cause over-stress problems on generators, transformers, circuit breakers (CBs), and transmission lines etc. On the other hand, the power systems are exploited to the limits of stability maintained by the generators. So the protection of electric power systems during short circuit conditions has become increasingly important. The most promising candidate to suppress this current is a fault current limiter (FCL) with high temperature superconductor (HTS) [1, 2]. SCFCLs can be classified into R-types (Resistive) and L-types (Inductive) by current limiting impedance. The L-type SCFCLs limit the fault current by inductance and have advantages of being able to limit the AC component of the fault current and to suppress the voltage drop at the faults. On the other hand, the R-type SCFCLs limit the fault current by resistance and have advantage of being able to consume the excessive energy at the faults. This feature may contribute to the power system stability improvement [3]. During the fault period, all the energy released is dissipated in the superconducting (SC) film. Because of this energy, the film temperature (Tsc) can reach high values within few milliseconds. One way of reducing this energy, and thereby limit the rise in Tsc, is to limit the fault current even further, for instance by increasing film resistance (Rsc). This can be achieved by increasing the film length ([pic]). However, increasing [pic] increases the volume of the FCL and the losses under non-fault conditions. An alternative way of reducing this energy is to reduce the current through the SC film, isc during the fault period by connecting shunt impedance across the SC film [4 – 8]. In this concept, during normal operation, the resistance of the SC film is essentially zero and steady-state current flows through it. However, during a fault, the resistance of the SC film increases to high value, so most of the fault current is diverted through the shunt impedance. Once the fault is cleared, the steady-state current can continue to flow without excessive heating in the the SC film. In this concept, the SC film is essentially a switch that commutates the fault current to the shunt impedance. For...
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