Optimal Protection Coordination of over current Relays in DG System with Solid State Fault Current Limiters

Abstract

In order to meet the increase in the power demand, Distributed Generation (DG) system plays a major role. Apart from generation it also faces many technical challenges, loss of harmonic control, voltage regulation and losses and changes in the relay coordination due to differences in short-circuit levels. In a system when a short circuit takes place it leads to severe damage as very high magnitude of fault current will be observed. These high magnitude short circuit fault currents eventually leads to coordination problem of Over current relays. To achieve proper coordination, time settings between the relays are optimized using several optimization techniques.

In present circumstances, occurrence of fault in a system have become high which greatly affect reliability of power system. To avoid discontinuities in the system, optimal relay time settings have to be determined which are associated with the fault current that has to be minimized. Here, in order to limit the transient fault current in the system, solid state fault current limiter (SSFCL) is designed. To determine the optimal relay time settings, a new optimization technique, hybrid PSOGSA is applied.

The reduction in the fault current magnitudes have been observed: without and with SSFCL. Proposed optimization technique has been evaluated by comparing the results for the system with and without DG. The programming is done in MATLAB software and was implemented on 4bus DG system in SIMULINK platform.