A comparative analysis of partial discharge in 13 combined insulation structures of 11 materials used in cast-resin dry-type transformers
Özet
Partial discharge (PD) in cast-resin dry-type
transformers (CRDTs) is an important issue that needs
to be overcome. In this study, PD in insulation materials
used in CRDT windings is investigated. Four types of samples are prepared using 11 different types of materials,
including epoxy resin, three-ply glued polyester insulation,
prepreg insulation, glass fiber mesh, polyester adhesive
tape, polyester film, polyimide film, rectangular conductors
with polyester insulation, round conductors with polyester
insulation, round conductors with enamel insulation, and
foil conductors without insulation, and subjected to PD
measurements. The samples are placed into a mold for resin
casting that is similar to those used to fabricate large castresin windings, and the material behavior is tested. PD measurements are carried out in the high-voltage laboratory of
the BEST Transformer Company. The measured data are
used as inputs to models of the samples that are simulated
using finite element analysis software to determine the PD
inception electric field. The PD patterns of the samples are
compared with well-known PD patterns in the literature.
Finally,a comparative analysis of the materials is performed,
and strong and weak materials against PD are identified.
The results of this study show that laminated insulation
materials or fiberglassmeshes, both with epoxy resin, which
have PD inception at a mean value of 3.4 kV/mm of electric
field intensity, are more susceptible to PD than the other
insulation materials investigated. In contrast, insulated conductors or nonlaminated polyester or polyimide films, all
with epoxy resin, which have PD inception above a mean
value of 5.3 kV/mm of electric field intensity,are robustto PD.
