In this paper, considered a degradation series that characterizes the technical condition of a gas turbine for transporting natural gas. The series was obtained by processing the data of the standard measuring system of the turbine. The task of determination the technical condition of the equipment by its operational parameters is relevant, since in the future it allows to reduce the part of thermal tests and switch to a system of maintenance and repair according to technical condition. The paper proposes an algorithm that can not only assess the level of technical condition, but also detect anomalies in the initial and output data. An expert analysis of anomalous zones in the degradation series of the considered gas turbine for the calendar year of operation was carried out.