Phasor Comparison and Differential Current-Based Earth Fault Detection for Low-Impedance Grounded Transformer in Microgrid

In a complex and deregulated environment of power systems, the protection of the transformer is crucial to improving the stability of the entire power system. The probability of line-to-ground fault, i.e., earth fault is maximum in star-connected winding of any star-delta, delta-star, and star-star transformer configuration. This paper presents improved Restricted Earth Protection (REF) to the star-connected winding of the transformer against earth faults. Zero sequence component-based differential and restrain currents are utilized for the protection of the transformer. To check the authenticity of the suggested scheme against earth fault in the star winding of the transformer, an additional phase angle comparison-based protection scheme is proposed in this article. The power system network is simulated in PSCAD software with a transformer and an algorithm based on differential protection and angle comparison is validated in MATLAB software. Various out-of-zone and in-zone line-to-ground transformer faults are imparted on a star-connected winding of the transformer to check the effectiveness of the proposed algorithm. It is to be noted that the proposed algorithm detects all types of earth faults with varying fault inception angles, and fault resistance and remains stable for kind of out-of-zone transformer faults. Looking at the result analysis, the scheme can be implemented for practical use and provides effectiveness in terms of transformer protection in the microgrid environment and power system stability at large.