Page 24 - CE_Industral_Journal_2015

Statistics Regarding

Transformer Servicing and Transformer Life

AbStRACt Aging insulation directly relates to the lifespan of the
To increase the service life of transformers, various equipment transformer. As the oil oxidizes and the paper insulation
and service providers have offered different solutions, ages, the heat dissipation capability within the transformer is
including testing, online monitoring, oil treatment, and other compromised due to the formation of sludge deposits. The
services. These services have identified thousands of paper insulation’s remaining life is determined by its Degree
transformers as unreliable, allowing replacement units to be of Polymerization (DP). When the paper insulation has
secured prior to an unplanned outage. This paper examines reached a DP of 200, the paper insulation is considered to
a very large data source to investigate how various oil be at the end-of-useful-life, according to IEEE standards [1].
treatments affect transformer service life. The data in this
paper was taken from the SD Myers database of over Over the past 50 years, SD Myers has collected data
40 million oil testing records. The findings reveal a strong on thousands of transformers that have had preventative
correlation between average service life and the number of measures preformed on them [2]. The database mined in
oil services performed. this paper contains over 40 million fluid test results. Over
1500 records of out-of-service transformers were selected
IntRodUCtIon for study, including records for whether these transformers
The life of a transformer has long been accepted to be were serviced or non-serviced. This paper demonstrates
predominately based on the life of the paper insulation. the transformer life extension realized by oil processing
Insulation damaged by heat, moisture, or acids from aged services.
oil is less able to withstand line faults and other stresses
in the transformer. This paper investigates the effects of oIL SERVICES: EFFECtS on tRAnSFoRmER
performing services on the oil and paper insulation. LIFESpAn
As transformers age, they have increasing levels of moisture,
For the past half century, the effects of transformer oil acid, and furans. The moisture and acid are specifically
oxidation have been studied, theorized, and presented. harmful to the solid insulation. Several oil services were
When oxygen, moisture, and heat are present, oil oxidation considered that help reduce moisture, acid, and help
is inevitable. To address the effects of oxidation, service preserve the paper insulation. The oil services investigated
vendors and equipment providers have offered various in this study included oil reclamation, moisture reduction,
solutions, including testing, online monitoring, and oil and addition of oxidation inhibitor.
treatments, along with other services.

Figure 1: Acid levels in relation to life of cellulose insulation