transients in power system question

7/30/2019 Transients in Power System question

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VINAYAKA MISSIONS UNIVERSITY

AARUPADAI VEEDU INSTITUTE OF TECHNOLOGY

DEPARTMENT OF EEE

M.E Power Systems Engineering.

SUBJECT : TRANSIENTS IN POWER SYSTEM

UNIT I

(PART - A)

1. What are the various types of power system transients ?

2. Define Isokeraunic level .

3. Draw the mathematical model of lightning .

4. what is the role of ground wire with reference to lightning ?5. What is pre discharge current ?

6. What is the significance of pre discharge current ?

7. A region has 100 thunder storm days in a year . A line wire has tower height 30m

with ground wire height at mid span hg = 24m . Calculate the probable no. of

strokes contacting 100km of line per year at anywhere on the line.

8. What is back flash over?

9. Write the equations to find (i) lightning strokes occurring over 1 square km per

year at any location and (ii) No. of strokes intercepted by 100 km of line per year

10. Calculate the stroke current taking an insulator voltage of 8000 KV , surge

impedance Zg= 150 ohm, Zc = 300 and Zm = 150 ohm and predischarge current Ipd

= 15,000 amp.

(Part B)

1. Explain various types of power system transients

2. Explain mechanism of lightning stroke to tower

3. Explain the general principles of lightning protection

4. Derive the expressions for voltage stress experienced by insulator when a stroke

contacts a tower and midspan.

5. (i)Derive the mathematical model for lightning

(ii) Explain the parameters and characteristics of lightning stroke


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UNIT II

(PART - A)

1. What is ferro resonance ?

2. What is current chopping ?

3. What is normal switching ?

4. Define abnormal switching ?.

5. Draw the recovery voltage of circuit breaker following a kilometric fault.

6. What are the three basic transforms used frequently in RLC series circuit ?

7. What is the significance of resistance in transients ?

8. Give two examples for abnormal switching .

9. What is kilometric fault?

(PART - B)

1 . Explain short line / Kilometeric fault.

2. Explain circuit closing transient.

3. Explain line dropping and load rejection.

4. Explain switching surges on integrated power systems.

5. Explain abnormal switching transients.

UNIT III

(PART - A)

1. Draw beweleys lattice diagram .

2. What is refraction coefficient ?

3. What is refraction coefficient ?

4. What is the relationship between reflection coefficient and

Refraction coefficient ?

5. A transmission line is 300 m long and open at the far end.Calculate the open end

voltage after 20 m sec when energized by a sterp of 1000KV if attenuation of

surge is 0.9 over one length of travel at light velocity

6. What is surge impedance ?

7. What is meant by attenuation of traveling wave ?


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8. What is meant by distortion of traveling waves ?

9. What is the condition for distortion less transmission?

(PART - B)

1. A transmission line has L = 1mh / km and C = 11.11n.f/km . conductor plus

ground resistance amounts to .4 / km. Calculate

(i) surge impedance

(ii) velocity of propagation

(iii) attenuation factor for 400 meters in Nepers

(iv) Maximum value of open end voltage

2. Explain how attenuation takes place in traveling waves using bewley lattice

diagram .

3. Derive the differential equations and their solutions in time domain for traveling

wave.

4. Explain the traveling wave concept for a step function for the following

conditions

(i) Omitting all losses

(ii) Distortion less condition

UNIT IV

(PART - A)

1. What is shielding angle ?

2. What is shadow angle ?

3. What is shadow width ?

4. What is the use of ground wire ?

5. What are the types of tower of footing resistances used ?

6. What is the use of rod gap ?

7. What is the function of surge diverter ?

8. What is meant by insulation co ordination ?


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9. What is the purpose of lightning arrester?

10. What are the devices used for lightning protection?

(PART - B)

1. Explain design factors of EHV lines .

2. Write short notes on : (i) Shielding wire

(ii) rod gap

(iii) Surge diverter

3. Write the hierarchy of insulation coordination.

4. Explain the different methods employed for lightning protection of overhead

lines?

5. Write note on the following

(i) Tower footing resistance

(ii) Lightning arrester

Unit V

Part A

1. Develop the model for distributed parameter transmission line

2. Develop the model for transmission system with lumped parameters

3. Write the equations for voltage and current at any point on a line

4. Draw the standing waves of voltage and current at power frequency

5. Write the special expression for voltage and current for an open circuit

6. Write the special expression for voltage and current for matched line

7. Write the special expression for voltage and current for short circuit

8. what are the three type of excitation mainly used in traveling wave studies?

9. Write the expression for propagation factor


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Part B

1. Obtain the solution for an open circuited transmission line in laplace

transform

2. Obtain the solution for a short circuited transmission line in laplace transform

3. Obtain the solution in laplace transform for a transmission line which is

terminated with a line having matched impedance

4. Derive the transient response of systems with series and shunt lumped

parameters

5. A transmission line has L = 1mh / km and C = 11.11n.f/km . conductor plus

ground resistance amounts to .4 / km. Calculate reflection factor and

refraction factor at the load if the line is terminated in a load of 500 ohm

transients in power system question

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