Comprehensive analysis of on-site method for determining synchronous reactance

Knowing the exact parameters of a turbogenerator is essential for the analysis of its operation, control, maintenance
and performance. Some generator parameters may change over time. The most common changes occur
due to the degradation of the magnetic characteristics of the generator. This paper points out the limitations of
the on-site measurement method (IEEE Std 1110, Annex D) for calculating saturated synchronous reactances of a
turbogenerator. It has been proven that the method from the standard is highly sensitive even to a small error
(1–2%) in determining the unsaturated synchronous reactance along d axes. The error occurs when the impact of
magnetic hysteresis is neglected and the no-load and short-circuit tests are not conducted after the over-haul of a
turbogenerator. The paper proposes improvements for reducing the disadvantages of the on-site methods.
Furthermore, several weaknesses of this method have been identified and the proposed corrections are detailed
herewith. The improvements shown in this paper are suitable for the use in steady-state analysis of turbogenerators.