Electrical Power Engineering

Kindly find below two parts to be solved: Problem 1 Two single-phase transformers are connected open-Y open-Δ to provide power for a three-phase Y-connected 100-kVA load with a 0.80 lagging power factor and a 50-kVA single-phase load with a 0.90 lagging power factor, as shown in Figure 1. Assume that the primary-side voltage of the bank is 7620/13,200 V and the secondary-side voltage is 240 V. Using the given information, calculate the following: (a) The line current flowing in each secondary-phase wire. (b) The current flowing in the secondary winding of each transformer. (c) The kilovoltampere load on each transformer. (d) The current flowing in each primary-phase wire and in the primary neutral. Figure 1: open-Y open-Δ connection ========================= 1 Problem 2 Assume that a 250-kVA distribution transformer is used for single-phase pole mounting. The transformer is connected phase-to-neutral 7200 V on the primary, and 2520 V phase- to-neutral on the secondary side. The leakage impedance of the transformer is 3.5%. Based on the given information, determine the following: (a) Assume that the transformer has 0.7 pu A in the high voltage winding. Find the actual current values in the high- and low-voltage winding. What is the value of the current in the low-voltage winding in per units? (b) Find the impedance of the transformer as referred to the high- and low-voltage windings in ohms. (c) Assume that the low-voltage terminals of the transformer are short-circuited and 0.22 puV is applied to the high-voltage winding. Find the high- and low-voltage winding currents that exist as a result of the short circuit in pu and amperes. (d) Determine the internal voltage drop of the transformer, due to its leakage impedance, if a 1.2 pu current flows in the high-voltage winding. Give the result in pu and volts.