Wyes and wye nots of three-phase distribution transformer connections

The advantages and disadvantages of various three-phase transformer connections are summarized. Recommendations are provided regarding the standard types of connections a utility should offer for various service requirements. Warehousing costs, ferroresonance, neutral grounding, core construction, overvoltages, unbalanced loading, zero sequence source, and through faults are considered. Emphasis is placed on the exchange of information between customer and utility. An Application for Three-Phase Service form is provided. It can be used to determine service requirements including voltage, grounded, ungrounded, three-phase load, single-phase load, motor characteristics, and fault current interruption rating of secondary breakers and switchgear. Suggestions on utility-supplied information such as maximum available three-phase and line-to-ground fault currents and a discussion of the operation of ungrounded systems are also provided