Consider a three-phase 1,500 kVA transformer to step down the voltage from 13.8 kV to 480Y/277 V. The transformer is old and needs to be replaced. Two options are available: (i) replace it by the same transformer with an efficiency of 98.6 percent and an installed cost of $45,000 and (ii) replace it by a more energy-efficient transformer with an efficiency of 99.0 percent and an installed cost of $60,000.

a. Determine the best option for the transformer replacement considering a lifetime of 25 years, and electricity price of $0.06, a discount rate of 4.1 percent, and an average load factor of 50 percent.

b. Determine the electricity price for which the energy-efficient motor is not cost-effective using the same assumptions of question (a).

c. Determine the size of the main secondary feeders for both the standard and the energy-efficient transformers. Calculate the energy savings if the next higher feeder size is used.