Example 8. A hydro-electric power station has a reservoir of area 2-4 square kilometres and capacity 5 x 10° m'. The effective head of water is 100 metres. The penstock, turbine and generation efficiencies are respectively 95%,90% and 85%. (i) Calculate the total electrical energy that can be generated from the power station. (ii) If a load of 15,000 kW has been supplied for 3 hours, find the fall in reservoir level.

2. a) Explain the terms load factor and diversity factor. b) Discuss the advantages of interconnected grid system. c) A generating station is to supply four regions of load whose peak loads are 10 MW, 5 MW, 8 MW and 7 MW. The diversity factor at the station is 1-5 and the average annual load factor is 60%. Calculate: (i) the maximum demand on the station, (ii) annual energy supplied by the station and (iii) suggest the installed capacity and the number of units.

By comparing the principle of operation of a "three" phase generation system with a single-phase system, state what are the bendfits of three phase systems? In your own words, define the "skin effect" in transmission lines and discuss how can it be minimised? Name three advantages of AC transmission in comparison to DC transmission. What are the units of active, reactive and apparent power? The current in a single-phase motor lags 50° behind the voltage. What is the power factor of the motor?