This guide addresses the application of tertiary and stabilizing windings in liquid immersed power transformers@ as covered by IEEE Std C57.12.00@ as well as recommendations to evaluate the need or convenience of having such windings. The primary application of this guide is for transformers and autotransformers with wye-wye connected windings@ with or without a delta connected tertiary or stabilizing winding. The guide does not address tertiary windings in conventional delta-wye@ or delta-delta connected transformers. Purpose This guide provides users with a conceptual framework and recommendations for the specification@ application@ and performance evaluation of tertiary and stabilizing windings.