System Model and Per Unit T1 Line T2 BE ji0/km BE 31.25miles 3C Impedance Load R1.jXi.-0.1+j0.5 p.u. 30 MVA 14 kV 30 MVA 13 kV TYA X-0.1 p.u. 13/220 kV X-0.2 p.u. 35 MVA * Transformer T2 is composed of "three single-phase" transformers, each rated 40/3 MVA, 132.8:14 kV with a leakage reactance of 0.1 per unit. (a) Fill in the appropriate base values. Gen. G Trans T Line Trans. Ta Load New MVA Base New KV Base (b) Calculate the impedance values. Gen G Trans. T1 Line Trans. T2 Load Pu. Impedance

What is the definition of zero sequence impedance in transformer? What is the benefit of zero sequence impedance in transformers?

3.8. Three identical 9-MVA, 7.2-kV/4.16-kV, single-phase transformers are con- nected in wye on the high-voltage side and delta on the low voltage side. The equivalent series impedance of each transformer referred to the high-voltage side is 0.12 + j0.82 S per phase. The transformer supplies a balanced three- phase load of 18 MVA, 0.8 power factor lagging at 4.16 kV. Determine the line-to-line voltage at the high-voltage terminals of the transformer.

2. Given three identical ideal single-phase transformers with each rated at 100KVA and 7kV/3.5kV, they are connected as a three-phase transformer bank. The three-phase transformer has high voltage side connected in delta and the low voltage side is connected in wye. A three-phase 200KVA, wye connected load is connected at the low voltage side of the transformer. Calculate the following: a. Rated line-to-line voltage on each side b. Line current on each side of the transformer