Dielectric testing and corona inspection of a 14.4-KV, 1800 RPM centrifugal compressor motor stator insulation system

Factory acceptance tests (FAT) of a new high voltage rotating machine include comprehensive diagnostic tests of the finished stator winding insulation system. The end user obtains baseline data for condition monitoring performed during the machine´s operating life. The design geometry of stator windings and manufacturing processes used to produce them will affect the dielectric test results. There is a significant challenge in comparing test results from different stators to obtain a statistically useful sample for an acceptance test database. This paper compares dielectric test results from the 14.4-kV windings of several new 1800 rpm, 26.1 MW (35000 hp) centrifugal compressor synchronous motor stators of identical design, built for two US chemical plants. The results are compared to those from accompanying sacrificial coils. The stator diagnostic tests include dissipation factor (DF, or tan delta), power factor tip up (PFTU, or delta tan delta), offline partial discharge (PD), corona inspection with a UV analyzer, and online PD. Sacrificial coils produced and processed alongside each stator received the specified API coil acceptance tests, plus corona inspection with a UV analyzer. PD measurements on the sample coils were repeated at elevated voltage, and the results compared to the corona inspection observations. The paper shares the comparative analysis of the stator- and coil test results as an excellent example of baseline FAT data.