Generating Electrical Power: QUIZ

Practical level:

--1 Explain the difference between a base load and a peak-load generating plant.

--2 Why are nuclear power stations not suited to supply peak loads?

--3 Referring to the coal mine, we have the choice of hauling the coal to a generating plant or installing the generating plant next to the mine mouth. What factors come into play in determining the best solution?

--4 What is the best indicator of stability (or instability) of an electric utility system?

--5 What is meant by the term network?

--6 Give two reasons why electric utility systems are interconnected.

--7 The river flow is 5000 m^3/s at a height of 24 m. Calculate the available hydraulic power.

--8 Explain the operating principle of a thermal plant, a hydropower plant, and a nu clear plant.

--9 Name two basic differences between a light-water reactor and a heavy-water re actor.

--10 Explain what is meant by moderator. fission, fusion, neutron, and heavy water: Intermediate level

--11 The Zaire River, in Africa, discharges at a constant rate 1300 km^3 of water per year.

It has been proposed to build a series of dams in the region of Inga, where the river drops by 100 m.

Calculate:

a. The water flow ( m^3/s )

b. The power that could be harnessed [MW]

c. The discharge in cubic miles per year

--12 For how long does a 1500 MW generator have to run to produce the same quantity of energy as that released by a 20 kiloton atomic bomb? (See conversion charts)

--13 The demand of a municipality regularly varies between 60 MW and 110 MW in the course of one day, the average power being 80 MW. To produce the required energy, we have the following options:

a. Install a base-power generating unit and a diesel-engine peaking plant.

b. Install a base-power generating unit and a pumped-storage unit.

What are the respective capacities of the base power and peaking power plants in each case?

--14 On a particular day, the head of Grand Coulee dam is 280 ft and the generators deliver 6000 MVA at a power factor of 0.9 lagging. Assuming the average turbine efficiency is 0.92 and the average generator efficiency is 0.98, calculate the following:

a. The active power output, MW

b. The reactive power supplied to the system

c. The amount of water flowing through the turbines [yd^3/s]

--15 Explain the principle of operation of a cooling tower.

--16 A modern coal-burning thermal station produces an electrical output of 720 MW. Calculate the approximate value of the following:

a. The amount of coal consumed [tons (not tonnes) per day]

b. The amount of smoke. gas, and fly ash re leased [tons per day]

c. The cooling water flowing through the condenser. assuming a temperature rise of 10°C /m^3/s]

--17 In Problem 16, if a cooling tower is required, how much water must be drawn from a local stream [m^3/s]? Can this water be recycled?

--18 A fuel bundle of natural uranium dioxide has a mass of 22.2 kg when first inserted into a heavy-water reactor. If it releases an average of 372.5 kW of thermal energy during its 19-month stay in the reactor, calculate the following:

a. The total amount of heat released [J ] and [Btu]

b. The reduction in weight of the bundle. due to the energy released [g] Advanced level 19 a. Calculate the annual energy consumption TW-h of the electric utility system having the load duration curve.

b. If this energy were consumed at an absolutely uniform rate. what would the peak load be GW?

--20 The temperature of the heavy-water coolant drops from 294°C to 249°C in passing through the heat exchangers. Knowing that the reactor is cooled at the rate of 7.7 t/s of heavy water, calculate the heat [MWJ transmitted to the heat exchangers (specific heat of heavy water is 4560 J/kg).

Industrial Application

--21 On November 12, 1992, at 10:09 AM a large generator on the East Coast tripped out, causing the interconnected power pool of 18 823 MW to suddenly lose 1050 MW of generating power. In a matter of seconds, the system frequency fell from 60 Hz to 59.97 Hz. The power output of the other generators on the system was selectively in creased and the rated 60 Hz frequency was restored after an interval of about 7.5 minutes. The frequency was then raised above 60 Hz for a time to recover the cycles lost, thereby correcting the electric clocks. The behavior of the frequency before and after the incident is shown.

Calculate:

a. The average frequency during the 7.5 minute restoration period

b. The number of cycles generated during the 7.S-minute period

c. The number of cycles that would have been generated during the 6-minute interval if the accident had not occurred and the frequency had stayed at 60 Hz

d. Electric clocks are designed so that the minute hand makes one complete turn in exactly one minute when the frequency is exactly 60 Hz. How many turns did the minute hand make during the 7.S-minute interval? What is the error in the minute hand reading, expressed in milliseconds?

--22 In Problem 21 we assume that half the 18 823 MW load consists of induction motors. Some motors drive fans and similar loads wherein the power varies as the cube of the speed. Calculate the drop in power of a 10000 hp blower motor when the frequency falls from 60 Hz to 59.97 Hz.

--23 A summer camp is located near a 55 ft waterfall. Tests show that the stream delivers a minimum of 270 cubic feet per minute in the course of a year. It’s proposed to in stall a 3-phase induction motor and drive it as a generator. Calculate the approximate horsepower of the motor that could harness 80% of the capacity of the falls.