Certain investigations on loss of excitation protection scheme for synchronous generators

Abstract

As industrial technology evolves and advances, power systems are newlineconstantly modified and upgraded. In a power system, synchronous generators newlineserve as the main source of electricity generation. These synchronous generators newlinemay experience anomalous conditions and faults may be of internal or external newlinefaults or even both. These conditions may affect both generator and power newlinesystem. Hence, it is necessary to protect the synchronous generators by using newlinesuitable protection devices before any failure occurs, to maintain stability. In a newlinesynchronous generator, the excitation system is essential since it keeps the newlinegenerator in synchronous with the grid. The occurrence of outages in excitation newlinesystem lead to excitation failure (Loss of Excitation) in synchronous generators. newlineAmongst other faults Loss of Excitation (LOE) grabs foremost attention since it newlinecauses instability in synchronous machines as well as in power systems. newlineThe Failure of Excitation (LOE) makes the synchronous machine newlineincapable of controlling the machine parameters such as terminal voltage, newlineresistance, current, reactance, load angle, real and reactive power. The distortion newlinein the magnetic coupling between the stator and rotor causes the machine to newlinefunction as an induction generator results in absorbing reactive power from newlinethe power system. As a result, the power network becomes unstable. newlineThe conventional protection method for LOE is based on impedance trajectory newlineof the machine with negative offset mho relay proposed by Mason and Berdy. newlineMeanwhile, the traditional method experiences malfunctions due to power swing newlineconditions caused by a three phase fault in the transmission line or bus near the newlinegenerator. Also the traditional method experiences a speed dip in LOE detection. newlineHence, in this research, focus is made on new approaches to detect and newlinediscriminate LOE from power swing conditions in a power system. newline