ABSTRACT
Phasors and transformer polarity are important in analyzing, documenting, and understanding power system operation and the currents and voltages associated with faults and unbalances. The international standard is that phasors always rotate in the counterclockwise direction. The circuit diagram identifies the specific circuit involved with the location and assumed direction for the currents and the location and assumed polarity for the voltages to be documented in the phasor diagram. The polarity indications for transformers are well established by standards that apply to all types of transformers. There are two varieties of polarity: substractive and additive. "Phasor" and "phase rotation" are two entirely different terms, although they look almost alike. Ac phasors are always rotating counterclockwise at the system frequency. The circuit diagram identifies the specific circuit involved with the location and assumed direction for the currents and the location and assumed polarity for the voltages to be documented in the phasor diagram.
