Hamid Yaghobi - Department of Electrical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
Hashem Mortazavi - Khorasan Regional Electric Company (KREC), Iran
Kourosh. Ansari - Department of Electrical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
Habib Rajabi Mashhadi - Department of Electrical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

Synchronous generator Loss of Excitation (LOE) if dose not detected rapidly; not only has a harmful affect on the generator, but also has a devastating impact on power system stability. This paper presents a novel method for detecting Loss of Excitation in synchronous generator based on change in the magnetic flux linkage. Generator air gap flux linkage is measured via search coils sensor installed under the stator wedges. The searchcoil sensor is widely used in electrical machine monitoring in recent years. Theoretical approach based on Finite Element Method (FEM) together with experimental results derived from a 4-pole, 380V, 1500 rpm, 50 Hz, 50 KVA, 3-phase salient-pole synchronous generator confirm the validity of the proposed method. Extensive simulations show that the proposed method has various distinct features that are advantageous over existing schemes. Speed and sensitivity are the main points featured in the proposed method. The effectiveness of the proposed protection is demonstrated by comparing with conventional LOE protection.

Synchronous generator, loss of excitation protection, FEM, linkage flux, search coil