JNTU B.Tech II POWER SYSTEMS I Previous Question Paper (December - 2018 - R15)

Give a neat schematic of arrangements of the various parts of a nuclear reactor with heat exchange, and explain.

Load factor for the station is 80%. The generator efficiency may be taken as 97% and the thermal efficiency of the turbines as 28%, the boiler efficiency as 77% and the overall thermal efficiency of the whole station as 20.5%. (i) Choose the main equipment for the station. Find the size of each generator, turbine and boiler used. Give the main specification.

Discuss steam station controls with reference to boiler control, turbine control and electrical control.

Draw the block diagram of gas power stations.

With the help of neat sketches, explain about different types of distribution systems.

A single phase distributor 2 km long supplies a load of 120 A at 0.8 power factor lagging at its far end and a load of 80 A at 0.9 power factor lagging at its midpoint. Both power factors are referred to the voltage at the far end. The resistance and reactance per km (go and return) are 0.05 ohms and 0.1 ohms respectively. If the voltage at the far end is maintained at 230 V, calculate (i) voltage at the sending end (ii) Phase angle between the voltages at the two ends.

Explain about a method of solving single phase AC distribution system in which the power factor of loads are referred to respective load voltages.

A 3-phase, 4 wire system with 400 V line voltage supplies the following loads (i) A 400 V, 3-phase, 75 HP motor works at 0.8 p.f lagging with an efficiency of 88%. (ii) A 15W unity power factor load connected between phase A and neutral. (iii) A 12.5 kW, 0.866 leading p.f load connected between phase B and neutral. Calculate (1) the neutral current (2) the three line currents (3) total power delivered by the supply. Phase sequence being ABC.

List out various bus-bar schemes and explain.

In a 3-phase, 4-wire distribution system with 240 volts between lines and neutral there is a balanced motor load of 250 kW at 0.8 power factor. Lamp loads connected between respective lines and neutral absorb 25, 75 and 100 kW. Calculate the current in each line and in the neutral wire of the feeder cable.

Give the layout of a substation showing the location of PT’s and CT’s.

Draw the layout diagram of gas insulated substations.

What are the disadvantages of low power factor?

A 3-phase overhead line has resistance and reactance per phase of 5Ω and 20 Ω respectively. The load at the receiving end is 25 MW at 33 kV and a power factor of 0.8 lagging. Find the capacity of the synchronous condenser required for this load condition if it is connected at the receiving end and the line voltages at both ends are maintained at 33kV.

Mention the importance of voltage control.

An Industrial load takes 80,000 units in a year, the average power factor being 0.707 lagging. The recorded maximum demand is 500 kVA. The tariff is Rs. 120 per kVA of maximum demand plus 2.5 paise per kWh. Calculate the annual cost of supply and find out the annual saving in cost by installing phase advancing plant costing Rs. 50 per kVAR which raises the p.f from 0.707 to 0.9 lagging. Allow 10% per year on the cost of phase advancing plant to cover all additional costs.

How would you find the economic loading of base load and peak load stations for a given load duration curve?

A generating station has a maximum demand of 75 MW and a yearly load factor of 40%. Generating costs including station costs are Rs. 80 per annum per kW demand plus 1 paise per kWh transmitted. The annual capital charge for transmission system is 20 lakhs and for distribution system Rs. 15 lakhs, the respective diversity factor being 1.2 and 1.5. The efficiency of transmission system is 90% and the distribution system is 85%. Find the yearly cost per kW demand and kWh supplied at substation and at consumer premises.

What are the various types of tariff’s? Name them and explain briefly about each of them.

A generating station has a connected load of 40 MW and maximum demand of 20 Mw. The units generated in an year are 60 × 10^6 kWh. Calculate the (i) Demand factor and (ii) Load factor.