Torsional Oscillations in a Gas Turbine Unit and the Possibility of Collapse of an Isolated Power System

Abstract

Low-frequency (sub-synchronous) oscillation effects in geared gas turbine units that lead to the shutdown of the units and to breakdown of the power system are examined. The reasons are complicated and depend on the operation of variable frequency drives and the design features of the gas turbine unit. Data from tests by the firm JSC “Diamekh 2000” are presented. This paper examines the features of oscillations in the reducing gear when resonant torsional oscillations are present in the drive sleeve. It is proposed that gas turbine units without, rather than with, gearing be used in isolated power systems for operation with a variable frequency drive and for maintaining the balance between the nonlinear and linear components of the load.