Simulation of negative phase sequence relay based on phase sensitive rectification

According to symmetric component theory, negative phase sequence in induction motors is caused due to unbalanced windings or due to the application of unbalanced supply voltages on the stator terminals. A magnetic field is created by this negative phase sequence component and this field rotates in the opposite direction causing a decrease in the motor output torque. In this article, a novel negative phase sequence detector for relaying for motor/generator protection and motor condition monitoring is proposed without using any negative sequence filter. In the proposed scheme, a phase sensitive rectification has been used for extraction resistive and reactive components of negative phase sequence current. A Matlab Simulink model has been developed to simulate the performance of phase sensitive rectification (PSR) and necessary computation of rms value of negative sequence component.