A Review of Generator Loss of Excitation Protection Schemes

Abstract

Loss of excitation (LOE) on synchronous machine is an abnormal operating condition which, if not detected, can have severe consequence. This paper aims at providing an in-depth analysis of the phenomenon, factors and the impact of LOE. It discusses the various protection schemes and provides the basis for selection of settings. The philosophy for coordinating loss of excitation protection with generator capability and steady-state stability limits is discussed. The performance of impedance and admittance schemes is analysed with the help of simulation. A case where loss of excitation protection is prone to incorrect operation for stable power swings is studied, which suggests the importance of dynamic studies for setting loss of excitation relay. The results suggest the need for intelligent relaying techniques for improving the reliability of LOE protection schemes. Finally, it discusses the latest advancements in the area of LOE protection.