A three-phase transformer bank consisting of three 10-kVA, 2300:230-V, 60-Hz, single-phase transformers connected in Y- is used to step down the voltage. The loads are connected to the transformers by means of a common three-phase low-voltage feeder whose series impedance is 0.005 + j0.01 Ω per phase. The transformers themselves are supplied by means of a three-phase high-voltage feeder whose series impedance is 0.5 + j5.0 Ω per phase. The equivalent series impedance of the single-phase transformer referred to the low-voltage side is 0.12+j0.24 Ω. The star point on the primary side of the transformer bank is grounded. The load consists of a heating load of 2 kW per phase and a three-phase induction-motor load of 20 kVA with a lagging power factor of 0.8, supplied at 230 V line-to-line.
(a) Draw a one-line diagram of this three-phase distribution system.
(b) Neglecting the exciting current of the transformer bank, draw the per-phase equivalent circuit of the distribution system.
(c) Determine the line current and the line-to line voltage at the sending end of the high voltage feeder.