Determination of saturated synchronous reactances of synchronous machines by using air-gap permeance distributions

This paper presents a new approach to the determination of the saturated values of synchronous reactances, based on permeance distributions in the air-gap inside a synchronous generator. It is shown that the permeance distributions can be obtained easily for any operating condition, by using air-gap fluxes measured by a search coil wound around a stator tooth of the generator. The permeance distributions are utilized to estimate saturation level in the air-gap. The paper shows that the saturated values of synchronous reactances are successfully determined by the proposed permeance method under various operating conditions in a power system installed in a laboratory. The results obtained are compared with those by a conventional method.