1 P.T.O.

ED72.07: Power Systems Design and Operation

EPSM, Energy Program

SERD, AIT Bangkok

Mid-Term Examination (August 2010 Term) Dr. J. G. Singh

Time duration: 2:00 Hrs (October 7, 2010) Maximum Marks: 100

Note: Attempt all questions. Make suitable assumptions wherever required. Mark distribution

is given in right hand side bracket. Please write neat and clean.

Question No. 1:

(a) Write true (T) or false (F) of the following. (101=10) i. Skin effect occurs only in DC system.

ii. There is no corona loss in HVAC system. iii. For sudden increase in load, frequency will decrease. iv. Buchholz relay is used for protecting generators in power system. v. Distance relays are used for the protection of transmission lines.

vi. Generators normally produce voltages in the range of 11-25kV. vii. Oil circuit breakers are not good for extra high voltage transmission lines.

viii. Converters and inverters are required for HVDC transmission. ix. In power system, travelling waves are produced only due to transients. x. Lighting and switching surges are ranges between 20 ms to 30 seconds.

(b) Fill in the blanks with suitable options to make statement correct. (101=10) i. The simplest type of relay is .

ii. . is the main cause of transmission line outage. iii. The Homopolar used .polarity to have less Corona loss and Radio

Interference.

iv. Non linear silicon carbide can be used as a. v. For a 1500m head hydro power plant . turbine is ideal.

vi. The maximum transmission voltage that is available commonly is kV. vii. is the most common green house gas.

viii. The robustness of a system to remain in normal state even if some contingency

takes place is termed as . ix. . software package can be commonly used for analyzing fast transients. x. . is the most efficient power generating plant.

Question No. 2:

(a) Describe in brief and to the point any 6 terms. (102=20)

i. What is meant by combined cycle power plant? ii. Differentiate between distributed generation and dispersed generation.

iii. What is corona and how it can be minimize? iv. What is meant by Ferranti effect in electrical power system? v. What is meant by asynchronous link?

vi. State four advantages of FACTS controllers? vii. What is smoothing reactors and why using it in power systems?

viii. What are potential benefits and challenges in interconnected power system? ix. Name any three commonly found conventional and renewable generating stations. x. What are effects of not having proper earth electrodes and how solve it?

xi. What are major differences between SVC and STATCOM? xii. What do you understand about slack bus and its significance?

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Question 3: (65=30)

i. What are bundled conductors? State the advantages and disadvantages of them. ii. What are CDM power plants? Explain the advantage of such a power plant.

iii. List the salient features of interconnected operation of power system. iv. Differentiate between alert state and extremis state in power system operation. v. Explain the principle of operation of MHD power generation.

vi. What are advantages and disadvantages of HVDC system? vii. With suitable block diagram, explain the various operating stages in power system.

viii. With suitable diagram, explain the principle of operation of hydrogen oxygen fuel cell.

Question No. 4: (6+6+3=15)

You are assigned with a task of developing an electrical system for a small island village of

east Jawa in Indonesia. The project consists of 3 generators of 11 kV along with a single

transformer (11kV to 220kV) and 4 loads which are interconnected by 220kV transmission

network. No of substations identified is two and all the three generators are assumed to be

working in synchronism in a single power plant. The loads are classified into agricultural,

residential, industrial and commercial. With the assumption that, the generator capacity is

adequate to meet the demand, answer the following questions.

i. Develop the single line diagram of the above system ii. Draw a typical load duration curve for any of the working day in a week.

iii. Justify the suitability of your single line diagram design with the advantages and disadvantages. (Make suitable assumptions where ever so required)

Question No. 5: (2+5+8=15)

a) Explain why transient studies are important in power system? b) Starting from fundamentals, develop a suitable model for capacitor and resistor for

transient studies using Dommel technique

c) Figure shows a simple R-C circuit. Assuming the circuit is closed at t = 0, draw the equivalent circuit for transient studies using Dommel technique and find out the

current at following time steps=0, t=0.00001 and t = 0.00002. Assume Vs = 100

cos(314.16t);C = 10F and R = 100 ohms ; Step size = 10 s.

.............. End .

R C Vs

Figure 1. Simple R-C Circuit