What Are the Grades of Transformer Insulation Paper?
Quick answer — Transformer insulation paper is graded by its thickness, density and finish, and the type (kraft, thermally-upgraded, aramid, crepe). The grade is chosen for the dielectric stress, the mechanical duty and the temperature. Higher grades (denser, thermally-upgraded or aramid) withstand more stress and heat and are used where the design demands it, while standard kraft is used for the bulk of the winding insulation.
What grades of insulation paper are used?
The types
Kraft (standard), thermally-upgraded kraft (TUK), crepe paper (for stretches and leads), aramid (high temperature) and pressboard (structural). The type sets the thermal and dielectric class.
The grade
Thickness, density and finish (and the oil absorption) are chosen for the void-free dielectric path, the mechanical and the electrical duty.
Choosing
Pick the paper by the voltage, the temperature rise, the mechanical forces and the oil compatibility; denser, higher-grade paper for the high-stress areas.
References & standards
- IEC 60554 (cellulose paper)
- IEC 60076-1
Related
Related manufacturers
Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp
Related components
Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.
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