A complete logic based backup protection scheme for three and six phase transmission system by using negative sequence currents

The conversion of existing three phase double circuit transmission line into Six phase transmission line will bridge the gap between power generation and power demand. As the Six Phase system can be considered as two mutually coupled Three Phase Systems, hence the protection scheme applicable for Three Phase Transmission Line will work for Six Phase Transmission system without any change. In this paper the author has developed a complete Logic Based backup protection scheme for six phase transmission system by using Negative sequence currents with Simulink platform of MATLAB. As the number of fault combinations in six Phase Transmission are 120, both the main protection and backup protection are complicate. The backup protection must be developed with utmost priority to protect the whole power system. The Proposed protection scheme is simulated for a Three Phase IEEE 9 Bus system and Six Phase Transmission line of Allegheny Power System, USA. This Scheme works for Three Phase System and also for Six Phase System because the Relaying operation is developed on Single Phase operation. The simulation results are presented that the logical relay gives the trip signal of logic 1 for fault and logic 0 for healthy conditions. The main advantage of the scheme is that no hardware is required except the interface for both input and output to Simulink Model.