Modeling and applications of three winding transformers in industrial and commercial facilities part 2: Unbalanced and transient analysis

In a previous companion paper the usage and basic modeling of 3-winding transformers was discussed. This paper complements the first paper and covers the modeling for unbalanced and transient conditions that could also exist in industrial electrical systems. The modeling and presentation of 3-winding transformers is discussed in two parts. The first part discusses single and two phase-to-ground fault conditions and includes modeling of zero sequence impedances. The second part discusses modeling 3-winding transformers for harmonics, energization and voltage transients studies which require modeling in the Electromagnetic Transient Programs (EMTP). The importance of correct interpretation of 3W transformers parameters, correct selection of model and case studies are demonstrated for the subject conditions.