Monitoring for rotor shorted turns

The paper describes the Siemens´ (formerly Parsons´) Rotor Shorted Turn Monitor (RSTM). The monitor was developed in the early 1990s for application to large steam turbine driven generator rotors. At the heart of the RSTM is a mathematical algorithm which processes the signal from a search coil located in the air-gap. This analysis program is called in sequence for 1 to 4 generators by a supervisory program which records the results and presents them, in a variety of forms, to a PC screen. Many results were collected from one of the first RSTMs to be placed in service at a UK power station having rotors with a history of shorted turn indications. From these it was possible to assess the effectiveness on the analysis program in coping with the influence of magnetic saturation in the rotor teeth over a wide range of load. The paper also outlines alternative methods for detecting shorted turns, their causes and the case for continuous monitoring