Implementation of new condition monitoring methods for large variable speed electrical motors into established maintenance management systems

Abstract

Norwegian export of natural gas to the European continent and United Kingdom depends heavily on large variable speed drive (VSD) electrical motors. These types of motors were viewed as very reliable until multiple unexpected catastrophic failures occurred at various locations. A joint industry research and development project (JIP) was initiated to research new tools and methods for improving the condition monitoring of these large electrical motors. Section two of this thesis gives and overview of existing technology and methods in use today. This section explains the concepts of maintenance management philosophies and gives a basic introduction to condition monitoring methods and systems, and variable speed drive electrical motors. Section three presents promising new technology and methods that was matured and tested in the JIP project. Both online and offline methods are discussed. Section four presents aspects that needs to be considered to successfully implement new tools and methods into existing organisations. Critical issues such as data acquisition, analysis, and reporting are discussed. The importance of having a total system view by considering all aspects and integration of technology, man, and organisation (TMO) is highlighted. In section five a fault tree analysis (FTA) is presented for the top level failure "short-circuit caused by stator winding insulation breakdown". The contribution from the major fault groups have been estimated and each group and root causes are discussed. Section six discusses the subjects from the previous chapters and concludes that the new tools and methods from the JIP project represents major improvements in the condition monitoring of large VSD synchronous electrical motors.