Improving the Characteristic of Percentage Differential Relay of Power Transformer using Rogowski Coil with Extended Park’s Vector Approach

Percentage Differential Protection (PDP) is well- known as the main Unit Protection Relay of Power Transformer all over the world. The researchers suggested using a novel Current Transformer (CT) with a new approach for fault detections, to improve the characteristic of this relay. MATLAB Simulink tools software used to model the Rogowski Coil (RC), with the new PDP Relay characteristic. Reducing the min-operating level point and expanding the operation region by revoking the second slope in the characteristic of the relay by implementing Extended Park's Vector Approach (EPVA) for faults detection. The paper also sheds light on removing the saturation error curve from the total error in the characteristic of PDP relay using the linear CT characteristics of Rogowski Coil. Consequently, a better sensitivity achieved specially for small differential currents in the secondary system. By this method, good indications of quitting few currents on primary terminal of power transformer were achieved. This performance of algorithm is due to the EPVA's analyzation which depends on spectrum analysis.