Fault Detection on Critical Instrumentation Loops of Gas Turbines With Reflectometry

This paper deals with the testing of instrumentation loops (ILs) in gas turbines during scheduled maintenance. To both guarantee safe operation and save costs on periodical changing of cables, an innovative measurement device that monitors the status of the IL and indicates whether a replacement is necessary, has been developed. The goal of the research described in this paper is twofold: First, the cable network is checked for faults with time-domain reflectometry by comparing the recorded reflectogram with a reference reflectogram. Second, the sensor state is investigated by calculating its impedance through one-port scattering measurements. For this, a de-embedding technique is described to remove the cabling influences. Changes in the reflectogram or the impedance point to aging or a fault and indicate the location of the defect, so that specific actions can be taken to replace the malfunctioning cable or sensor.