A Relay Logic for Total and Partial Loss of Excitation Protection in Synchronous Generators

Loss of Excitation (LOE) is an important fault in synchronous generators which may cause the generator outage due to out-of-step(OS) conditions. Since the LOE protective relays act based on the impedance or admittance measurement at the generator terminals, they suffer from mal-operations caused by non-LOE phenomenon such as stable power swings. To preserve the security and dependability of the LOE protection, in this paper, some unique characteristics of LOE event are determined using the transient model of synchronous generators. In this paper, using the transient model of synchronous generators, some unique characteristics of LOE event are determined. Frequency decomposition and time domain analysis of active and reactive powers as well as the terminal voltages are used to define a suitable rule for LOE protection. A comprehensive list of full and partial LOE scenarios, power swing and other non-LOE scenarios at different loading conditions and topological configurations are considered. The input-output data of the simulated scenarios are then utilized by a support vector machine(SVM) to construct a relay logic for partial and total LOE protection. The efficiency of the proposed LOE protection algorithm is verified using a dynamic test system. The results are analyzed using performance criteria such as dependability, security and accuracy.