UL 1446A:2019 PDF Download

1 Scope

1.1 These requirements cover test procedures used in the evaluation of Class 120 (E) or higher rated electrical insulation systems (EIS) with operating voltages of 600V 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.

1.2 This outline is intended to evaluate a single EIS and establish a Voltage Stress Level [VSL] for the various insulation functions tested such as turn-to-turn, layer-to-layer, section-to-section, coil-to-coil and coil-to-ground. An EIS established under this outline is suitable for all transformers constructed with this EIS such that the design maintains the insulation thickness at or below the tested VSL values.

These requirements for the evaluation of an EIS do not establish thermal ratings for/or alter established thermal ratings for individual components.

1.4 These requirements do not cover insulation systems exposed to radiation or operating in oils,refrigerants, soaps, or other media that potentially degrade insulating materials.

1.5 When any performance aspect of an end-product requirement is not covered by this outline, the applicable standard shall be used.