Field results of monitoring partial discharges on in-service large power transformers

There is a desire within the electric utilities industry to add additional monitoring capabilities to their large power assets. This predominately pertains to large power transformers. Many utilities are currently monitoring oil and winding temperatures, dissolved gas, cooling systems and bushings. The next technology to implement is for partial discharges. Several successful installations of partial discharge monitoring equipment have been made during 2009 and 2010 on large power transformers up to and including 500 kV. This paper will review sensors used, sensor installation and noise cancellation methodologies as well as results from the various installations.