In this technical guide we will discuss the principles of transformer differential protection, walk you through detailed relay setting calculations, explore discrimination techniques that distinguish inrush current from real faults, and provide practical testing. In this technical guide we will discuss the principles of transformer differential protection, walk you through detailed relay setting calculations, explore discrimination techniques that distinguish inrush current from real faults, and provide practical testing. George Rockefeller is President of Rockefeller Associates, Inc. He has a BS in EE from Lehigh University, a MS from New Jersey Institute of Technology, and a MBA from Fairleigh Dickinson University. Rockefeller is a Fellow of IEEE and Past Chairman of IEEE Power Systems Relaying Committee. He. Core idea: Transformer protection detects electrical, thermal, pressure, gas, and insulation-related problems before a transformer failure damages equipment or spreads through the power system. Differential Protection (87) The most sensitive protection for internal transformer faults: Note: Differential. Fuses may adequately protect small transformers, but larger ones require overcurrent protection using a relay and CB, as fuses do not have the required fault breaking capacity. Fuses commonly protect small distribution transformers typically up to ratings of 1MVA at distribution voltages.
