Development of Digital Loss of Excitation Protection Algorithms for Synchronous Generators

A prominent phenomenon that disturbs synchronous generators is Loss of Excitation (LOE). It is a threat to power system too. After LOE, there is a reduction in internal voltage and rotor current of the generator. The absorption of reactive power from the system, leads the machine to act as an asynchronous generator when LOE occurs. In this context if the reactive power compensation is not done a major collapse can occur in the system. This paper depicts an algorithm for impedance based protection method with distance calculation for LOE condition. The algorithm for proposed protection method is developed, using Alternative Transients Program (ATP) Designer and PSCAD simulation software. The performance of the algorithms developed using both tools during LOE event on different operating conditions are studied and compared to find out the better performance of the algorithms. The results show that the ATP based algorithm is better for reliable protection against LOE conditions.