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.

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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.