Principles of Power Systems (V.K. Mehta) Solution Manual: Chapter Four

1. A distribution transformer costing Rs 50,000 has a useful life of 15 years. Determine the
annual depreciation charge using straight line method. Assume the salvage value of the equipment to be Rs 5,000.

2. The power generation equipment of a power station cost Rs 15,75,000 and has a useful life of 25 years. If the salvage value of the equipment is Rs 75,000 and annual interest rate is 5%, determine annual amount to be saved by sinking fund method. [Rs 31,400]

3. A 500 kVA distribution transformer costs Rs 50,000 and has a useful life of 20 years. If the salvage value is Rs 5,000 and annual compound interest rate is 8%, determine the value of the

transformer at the end of 10 years using sinking fund method.		[Rs 35,700]
4. A generating station has a maximum demand of 10 MW. Calculate the cost per unit generated from the following data :

	Annual load factor = 35% Capital cost = Rs 12,50,000

Annual cost of fuel and oil = Rs 8,00,000
Taxes, wages and salaries = Rs 7,00,000
Interest and depreciation = 10%

5. From the following data, estimate the cost per kWh for the generating station :

Plant capacity = 50 MW

Annual load factor = 40%

Capital cost = Rs 12 × 106

Annual cost of wages, taxes etc = Rs 4,00,000 ; cost of fuel, lubrication, maintenance = Rs

17,52,000 ; Annual interest and depreciation = 10% of initial value. [1·913 paise per kWh]

6. In a particular area both steam and hydro stations are equally possible. It has been estimated
that capital costs and running costs of these two types will be as under :

Plant
Hydro
Steam

Capital costk W
Rs 3000
Rs 2000

Running costkWh
3 paise
10 paise

Interest
5%
5%

If the expected average load factor is 40%, which is economical to operate, steam or hydro ?
[Hydro]

7. The energy cost of a 100 MW steam station working at 40% load factor comes out to be 12
paise/kWh of energy generated. What will be the cost of energy generated if the load factor is
improved to 60% ? The fuel cost of the power station due to increased generation increase the
annual generation cost by 5%.
[8·4 paise]

8. A load having a peak value of 50 MW and 45% load factor is to be supplied by a steam power
station in conjunction with a hydro-power station, the latter supplying 60 million units of energy per annum with a maximum output of 20 MW.

(i) Capital cost	Steam : Rs 2000 per kW installed Hydro : Rs 3000 per kW installed Coal Rs 150 per metric ton ; consumption being 0·5 kg per unit generated Steam : 0·7 paise per unit Hydro : 0·5 paise per unit Steam : 10% per annum Hydro : 9% per annum [11·6 paise]
(ii) Cost of fuel
(iii) Maintenance charges
(iv) Interest and depreciation
Calculate the average cost of energy.