Time- 2 hours Max. Marks 40 Min. Marks 14

Note:Part (a) of each unit is compulsory. Attempt any 2 parts from (b), (c)and(d)

UNIT-I1(a): Define string efficiency. (2)

1(b): Each of three insulators forming a string has a self capacitance of C farads. The shunting capacitance of the connecting metal work of each insulator is 0.2 C to earth and 0.05 to the line. Calculate: (6)

i) Voltage across each insulator as a % of line voltage to earth.ii) String efficiency

1( c ). Discuss why voltage distribution across units of a string insulator is not uniform & what are the methods for improvement? (6)

1(d). An overhead line has ACSR conductor of 1.95 cm diameter and a span of 244 m. The allowable tension is 3.56x104 N. Find:

a) Sag in still air condition with no ice coveringb) Vertical sag when there is an ice covering of 0.96 cm thickness and a

horizontal wind pressure of 382N per square metre of projected area. Ice weight 8920 N/m3.

c) The line is carried by insulator strings 1.43 m long. What should be the height of lowest cross arm to give a minimum ground clearance of 7.62 m under bad weather conditions? The conductor weight is 0.847 kg/m. (6)

UNIT-II2(a): What are the advantages of grounded neutral system? (2)2(b): Discuss the voltage transformer earthing. (6)2( c ): Discuss resistance grounding with neat phasor diagram. (6)2(d): A 33 KV. 3-ᶲ 50 Hz overhead line 60 Km long has a capacitance to ground of each line equal to 0.015µF per Km. Determine the inductance and KVA rating of the Peterson coil. (6)

B.E. 7th Semester (A) (EEE) Class Test-I (15-16)

Subject-Power Apparatus System

Time- 2 hours Max. Marks 40 Min. Marks 14

Note:Part (a) of each unit is compulsory. Attempt any 2 parts from (b), (c)and(d)

UNIT-I1(a): Define string efficiency. (2)

1(b): Each of three insulators forming a string has a self capacitance of C farads. The shunting capacitance of the connecting metal work of each insulator is 0.2 C to earth and 0.05 to the line. Calculate: (6)

iii) Voltage across each insulator as a % of line voltage to earth.iv) String efficiency

1( c ). Discuss why voltage distribution across units of a string insulator is not uniform & what are the methods for improvement? (6)

1(d). An overhead line has ACSR conductor of 1.95 cm diameter and a span of 244 m. The allowable tension is 3.56x104 N. Find:

d) Sag in still air condition with no ice coveringe) Vertical sag when there is an ice covering of 0.96 cm thickness and a

horizontal wind pressure of 382N per square metre of projected area. Ice weight 8920 N/m3.

The line is carried by insulator strings 1.43 m long. What should be the height of lowest cross arm to give a minimum ground clearance of 7.62 m under bad weather conditions? The conductor weight is 0.847 kg/m. (6)

UNIT-II2(a): What are the advantages of grounded neutral system? (2)2(b): Discuss the voltage transformer earthing. (6)2( c ): Discuss resistance grounding with neat phasor diagram. (6)2(d): A 33 KV. 3-ᶲ 50 Hz overhead line 60 Km long has a capacitance to ground of each line equal to 0.015µF per Km. Determine the inductance and KVA rating of the Peterson coil. (6)

B.E. 7th Semester (A) (EEE) Class Test-I (15-16)

Subject-Power Apparatus System

UNIT-III

3(a). Define bath Tub curve. [5]

3(b). Explain the term probability density function. What is exponential failure density? [5]3( c ). A tansmission line has span of 150 m between level support .The conductor has cross sectional area of 2cm2.The tension in conductor is 2000kg.If the specific gravity of conductor material is 9.9 gm/cm3 and wind pressure is 1.5kg/m length ,cal.sag and vertical sag. [5]

3(d) In a transmission line each conductor is at 20 Kv and is supported by string of 3 suspension insulator. The air cap[acitance between each cap. Pin junction and tower is one fifth of capacitance of each unit.A guard ring,effective only over the line end insulator unit is fitted so that voltage on two units nearest to the line end are equal.

1.Calculate voltage on line end unit.

2.Calculate values of capacitance Cx required [5]

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UNIT-III

3(a). Define bath Tub curve. [5]

3(b). Explain the term probability density function. What is exponential failure density? [5]3( c ). A tansmission line has span of 150 m between level support .The conductor has cross sectional area of 2cm2.The tension in conductor is 2000kg.If the specific gravity of conductor material is 9.9 gm/cm3 and wind pressure is 1.5kg/m length ,cal.sag and vertical sag. [5]

3(d) In a transmission line each conductor is at 20 Kv and is supported by string of 3 suspension insulator. The air cap[acitance between each cap. Pin junction and tower is one fifth of capacitance of each unit.A guard ring,effective only over the line end insulator unit is fitted so that voltage on two units nearest to the line end are equal.

1.Calculate voltage on line end unit.

2.Calculate values of capacitance Cx required [5]

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