Analysis of Online Partial Discharge Data Trending and Patterns Classification for Life Extension: A Survey of Large Ac Rotating Machines Installed in Petroleum and Chemical Industry

In the Petroleum and Chemical Industry, a rotating machine has to run reliably in service until a scheduled outage can be planned. In the 1980s and 1990s, some machines operated continuously for 3–5 years, but recently production demands push them to run as long as 5 – 8 years, especially, for some critical applications. These extended run times lead to an asset availability for maintenance once at the end of a 5-8 year run cycle. With opportunities stretched out, it is critical to have a well-defined maintenance scope and execution plan. Online partial discharge (PD) testing and monitoring has been widely applied to determine the need for maintenance of the stator winding insulation system and to help establish a more effective maintenance plan. Several high voltage rotating machines were selected to complete a survey with regards to their online PD trending along with the acquisition of several PRPD patterns. The PRPD patterns obtained contained characteristic features, which were successfully correlated with the observed trend, acquired during the service life of machines. The upward PD trend and correlation of source using phase-resolved PD (PRPD) patterns helped several end-users to determine when maintenance is advisable. During this survey, a few critical units were refurbished based on learning from this survey and then monitored again for an additional 5 years with significant financial savings.