Analysis of Phase Adjustment and Zero sequence Current Compensation With Y₀/Δ-11 Transformer Differential Protection

The modes and theories of two phase adjustment methods with Y₀/Δ-11 transformer differential protection are introduced. The theories and characteristics of Y₀ and Δ phase adjustment are analyzed. Their adaptability to earth fault inside and outside differential protection area is discussed, and the zero sequence current compensation is illuminated. The polarity zero sequence CT is analyzed. Results show that the phase adjustment is not only about the phase adjustment with different windings of a transformer but also related to the zero sequence current compensation with neutral point solid grounding side of a transformer. Combing Δ phase adjustment with the neutral point zero sequence current compensation can avoid differential protection’s incorrect action for earth faults outside the area, and can enhance the sensitivity to earth faults within area. Thus some transformers without specialized zero sequence differential protection can enhance their reactive ability to earth faults.