UL SUBJECT 1446A

This first issue of the Outline of Investigation for Investigation For Dry Type Transformer Insulation Systems Rated Above 1 kV, UL 1446A, covers the test procedures used in the evaluation of Class 120(E) or higher rated electrical insulation systems (EIS) with operating voltages of 1 kV and above for use in; open wound, cast coil, resin encapsulated and pre-preg flexible sheet rolled, dry-type high-voltage transformers where the thermal factor is the dominating aging factor and where transient over-voltages or partial discharge may be present.