Accuracy Standards for Phase-Shifting Transformers for Var Measurement

New accuracy standards are proposed for phase-shifting transformers generally applied in polyphase circuits for var (reactive volt-amperes) measurement. Limiting values of ratio correction factor (RCF) and phase angle defect (PD) are given for three proposed standard accuracy levels, namely, 0.3 per cent, 0.6 per cent, and 1.2 per cent. These levels represent the maximum error in var measurement owing to the phase-shifting transformer. The limiting values appear as circle diagrams. The proposals bring the standards up to the same level of development as those for instrument current and potential transformers.