Table of Contents

Toggle**Important RGPV Question**

**EX-404 (Power System-I)**

**IV Sem, EX**

**UNIT 1 An Overview of Electrical Energy Generation**

**Q.1** Draw and explain the structure and components of modern power systems with typical voltage levels.

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**Q.2** A 1000 mW power station delivers 1000 mW for 2 hours, 500 mW for 6 hours and is shut down for rest of each day. It is also shut down for maintenance for 60 days annually. Calculate its annual load factor.

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**Q.3** Explain load curves and load duration curves. Discuss their utility in the economics of generation.

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**Q.4** Write short notes on Comparison of isolated versus interconnected power system.

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**Q.5** A generating station supplied the following loads. 150 MW, 120 MW, 85 MW, 60 MW and 5 MW. The station has a maximum demand of 220 MW. The annual load factor of the station is 48%. Calculate

i) The number of units supplied annually

ii) The diversity factor and

iii) Demand factor

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**Q.6** Define the term diversity factor and prove that load factor of supply system is improved by an increase in diversity of load.

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**Q.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%. .

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** Q.8**Β Write short notes on Problems associated with modern large interconnected power system.

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**Q.9** Explain the Non-Conventional methods of Power generation.

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**Q.10** A generating station has the following data: Installed Capacity = 300MW; Capacity factor = 50%; Annual load factor 60% Annual cost of fuel, oil etc Rs. 9Γ107: Capital cost = Rs.109; annual interest and depreciation = 10%. Calculate

i) the minimum reserve capacity of the station

ii) the cost per KWh generated.

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**Q.11** Discuss in detail about power plant economics.

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**Q.12** Give the structure and components of power network.

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**Q.13** The yearly load duration curve of a power plant is a straight line. The maximum load is 500 MW and the minimum load is 400 MW. The capacity of the plant is 750 MW. Find the

i) Plant size factor

ii) Load factor

iii) Utilization factor

iv) Reverse capacity

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**Q.14 **Explain the effect of high transmission voltage on Power System.

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**Q.15** Write short notes on Demand factor and load factor

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**Unit 2 Transmission Line Components & Under Ground Cabling**Β

**Q.1** Derive an expression for capacitances of a single phase transmission system and discuss the effect of earth on capacitance with suitable equation.

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**Q.2** Compare the cross-section area of conductors for DC two wire system and 1 phase AC system assuming equal length, equal power and equal losses.

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**Q.3** Write short notes on Enumerate the different methods of grading of cables

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**Q.4** Derive a formula for the electric stress in a single core cable. Where is maximum stress? Where is it minimum?

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**Q.5** Discuss the concept of GMR and GMD in the calculation of transmission line inductance.

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**Q.6** A single core cable has a conductor diameter of 1 cm and internal sheath diameter of 1.9 cm. If impregnated paper of relative permittivity 4 is used as the insulation, calculate the capacitance for 1 km length of the cable.

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**Q.7** Write short notes on Derive the expression for dielectric stress of a single core cable.

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**Q.8** Derive the expression for Inductance of a single phase Two wire line.

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**Q.9** Calculate the Capacitance of a 100 km long 3-0,50 Hz overhead transmission line consisting of 3 conductors, each of diameter 2 cm and spaced 2.5 m at the corners of an equilateral triangle.

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**Q.10** Explain the Skin effect in Transmission line conductors.

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**Q.11** Explain the concept of GMR and GMD.

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**Q.12 **Explain about Ferranti effect with the help of phasor diagram.

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**Q.13** A 200 kV, 3-phase, 50 Hz transmission line 180 km long consists of three conductors of effective diameter 20 mm arranged in a vertical phase with 4 m spacing and regularly transposes. Find the inductance and kVA rating of the arc supressor coil.

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**Q.14** Explain the concept of self GMD and mutual GMD for evaluating inductance of transmission line.

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**Q.15** Discuss the advantages of using underground cables compared to overhead lines.

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**Β Q.16** Write short notes on Skin and proximity effect.

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**Q.17** Explain the basic difference between bundle conductors and composite conductors.

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**Q.18** Derive the expression for flux linkages of one conductor in a group of conductors.

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**Q.19** Draw the cross sectional view of shielded cables and describes its main parts.

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**Q.20** Why grading is necessary in cables? Explain different types of grading.

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**Q.21** Write short notes on Skin Effect.

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**UNIT 3 Transmission systems & performance of transmission line**Β

**Q.1** Deduce the expression for the sending end and receiving end power of a transmission line in terms of voltages and ABCD constants.

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**Q.2** A 50Hz, 3-phase transmission line is 280 km long. It has a total series impedance of (35+j140) ohms and shunt admittance of 930 x 10-6 siemen. It delivers 40,000 kW at 220 kV with 90% p.f lagging. Find the Generalized Circuit Constants, Sending end voltage and current. By using 7

i) Medium line nominal – T method

ii) Medium line nominal – ΟΒ method.

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**Q.3** Describe the concept and procedure to draw the power circle diagram.

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**Q.4** A transmission line has a span of 16 m between level supports. The cross sectional area of the conductor is 2.25 cmΒ³ and weighs 100 kg/100 m. The breaking stress is 4420 kg/cmΒ². Calculate the factor of safety if the 50g of the line is 3.5m. Assume a maximum wind pressure of 100 kg/m.

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**Q.5** Draw the phasor diagram of a short transmission line and derive an expression for voltage regulation and transmission efficiency.

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**Q.6** A 15 km long 3-phase overhead line delivers 5 MW at b 11 Kv at 0.8 lagging power factor. Line loss is 12% of power delivered. Line inductance is 1.1 MH per km per phase. Find sending end voltage and voltage regulation.

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**Q.7** Mention the various methods of voltage control in transmission line. Also explain any one method in details.

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**Q.8** Determine the efficiency and regulation of a 3-phase, 100 km, 50 Hz transmission line delivering 25MW at a.p.f. of 0.9 lagging and 66 kV to a balanced load. The conductors are of copper, each having resistance 0.1 ohm per km, inductance 0.1118 H per km and capacitance 0.9944 Β΅F per km. Neglect leakage and use nominal-n method.

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**Q.9 **Write short notes on :

a) Comparison between AIS & GIS Substation.

b) Interpretation of long line equation and its equivalent equation.

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**Q.10** Define regulation of a 3-Ξ¦Β short transmission system and develop an expression for approximate voltage regulation.

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**Q.11** A balanced 3-Ξ¦ load of 30 MW is supplied at 132 KV, 50 Hz and 0.85 pf lagging by means of a transmission line. The series impedance of a single conductor is (20+j52) ohms and the total phase-neutral admittance is 315 x 10-6Β siemens. Using Nominal T method, determine

1) A,B,C and D Constants of the line

ii) Sending end voltage.

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**Q.12** What is a Power Circle diagram of a transmission line? Explain how it can be constructed and what useful information can be obtained from it.

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**Q.13** Explain briefly about the methods of Voltage Control.

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**Q.14** Explain about Nominal T and Nominal it network models representation of transmission line.

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**Q.15** Explain about long transmission line and their representation.

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**Q.16** Discuss the effect of increase in voltage on the transmission line efficiency.

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**Q.17 **What do you understand by the constants of an overhead transmission line?

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**Q.18** Calculate A, B, C, D constants for medium transmission line with Nominal-t network.

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**Q.19** Determine the efficiency and regulation of a 3-phase, 100km, 50Hz transmission line delivering 20 MW at a p.f. of 0.8 lagging and 66kV to a balanced load. The conductors are of copper, each having resistance 0.1 ohm per km, 1.5 cm outside diameter, spaced equilaterally between centers. Neglect leakages and use Nominal -Ο OR Nominal T method.

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**Q.20 **Write short notes on Surge Impedance

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**UNIT 4 Insulator & Mechanical design**Β

**Q.1** A three phase overhead line is suspended by a suspension type insulator, which consists of three units. The potential across top unit and middle unit are 12 kV and 18 kV respectively. Calculate:

i) The ratio of capacitance between pin and earth to the self-Capacitance of each unit

ii) The line voltage

iii) String efficiency

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**Q.2 **Explain various types of insulators with neat diagrams and compare them.

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**Β Q.3** Describe the various methods to improve string efficiency.

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**Q.4 **A transmission line conductor having a dia of 18.5 mm weights 0.75 kg/m. The span is 285 metres. The wind pressure is 49 kg/mΒ² of projected area with ice coating of 12 mm. The ultimate strength of the conductor is 9000 kg. Calculate the maximum sag if the factor of safety is 2 and ice weighs 810 kg/mΒ³.

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**Q.5** Write short notes on What is difference between string chart and Sag template?

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**Q.6** What do you mean by string efficiency? Explain different method of improving string efficiency.

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**Q.7** In a 33 kV overhead line, three are there units in the string of insulators. If the capacitance between each insulator pin and earth is 11% of self-capacitance of each insulator, find the distribution of voltage over 3 insulators and string efficiency.

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**Q.8 **Derive the expression for voltage distribution in insulator string and string efficiency.

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**Q.9** What are the various types of line supports? Discuss suitability of each wire with reference to system voltage and span.

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**Q.10** Derive an expression for Sag due to weight of the conductor, when the supports are at the same level.

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**Q.11** Define String efficiency. Explain the methods of improving String efficiency.

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**Q.12** Write short notes on different types of insulators used for overhead lines.

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**Q.13** What is string chart and sag template?

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**Q.14** Discuss the usefulness of various materials used in insulting cables.

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**Q.15** Give comparison of monopolar and bipolar HVDC links.

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**Q.16** Suggest a method to equalize the voltage distribution across the insulators in an insulation.

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**Q.17 **Write short notes on Materials used for transmission line insulations

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**Q.18** Derive an expression for sag of a line supported between two supports of the same height.

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**Q.19 **Explain different types of insulators used for over head lines.

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**Q.20** Write short notes on Use of Sag templates

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**UNIT 5 Voltage control & Distribution system**Β

**Q.1** Write short notes on Explain the substation equipment’s.

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**Q.2** Draw the Single line diagram showing a typical arrangement of A.C. distribution system. State the requirements of ideal distribution system.

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**Q.3 **Describe the main limitation of Kelvin’s law. The cost of 3 phase overhead transmission line having cross-sectional area A cm2 is Rs [600+2800 A] per kW. Calculate the most economical current density for the conductor if the rate of interest and depreciation is 11% per annum. The cost of energy wasted is Rs 0.06/kwh. The resistance of each conductor is 0.16/A ohm/kM. Take load factor for Joss = 12%.

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**Q.4** Explain the Single bus bar system with Sectionalization and what are its merits and demerits.

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**Q.5** Make a list of the main equipments in a Substation and explain each in brief.

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**Q.6** Write short notes on AC 3 phase distribution.

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**Q.7** Describe different types of bus bar system.

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**Q.8 **Explain 3-phase 4 wire system of distributing electrical power.

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**Q.9** Draw the layout of an indoor substation and name the accessories.Β

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**— Best of Luck for Exam —**