An Enhanced Algorithm for Conventional Protection Devices of Transmission Lines With DTLR

As the installed capacity of renewable generation continues to increase nowadays to satisfy both emissions and economic requirements, the nature of intermittent generation results in a need to further increase transmission capacity. Dynamic thermal line rating may be used to increase the capacity of transmission lines without upgrading infrastructure. However, existing transmission line protection devices may mal-operate due to the increased capacity. So, it is required to evaluate the performance of existing protection devices. This paper proposes an algorithm that enhances the performance of existing conventional relays such as distance and overcurrent relays. The proposed algorithm is based on a combination of dynamic thermal rating, current ratio of negative and positive sequences and voltage criterion to detect faults whether symmetrical or asymmetrical and unsafe overload. In addition, it aims at restraining the existing relays during safe overloads. A model of a system under investigation is simulated, with studies performed in a MATLAB/Simulink environment. The results demonstrate the ability of the proposed scheme to detect all types of faults and unsafe overload dependably and restrain the conventional relays securely during safe overloads.