GTU BE FINAL YEAR ELECTRICAL

Testing and Commissioning of Electrical Equipments (2180901)

(1) Why the earthing resistance is kept minimum for safety of human being? What is the effect if earthing resistance is high? Explain three point method for measurement of earthing resistance.

(2) What is difference between equipment earthing and system grounding? Explain earthing procedure for substation.

(3) Which type of test is conducted on electrical equipment during its manufacturing process?

(4) Explain steps of drying out of big size of transformer.

5) Explain how the transformer group DY1 and DY11 is to be tested.

(6) Explain routine maintenance procedure for a power transformer.

(7) Explain test methods for Temperature rise of Transformer as per IS 2026.

(8) Explain Vector group of transformer.

(9) How the switching impulse test and high voltage test is conducted on transformer?

(10) Why the tape changer is kept on HV side of transformer? Give your justification.

(11) State various troubles, causes and preventive actions for failure of Power transformer.

(12) For below listed troubles in power transformer, state its causes and remedies:
a) Internal short circuit b) Overheating c) Rapid deterioration of oil.

(13) Explain the no load test and blocked rotor test of an induction motor. What data such test
provides?

(14) Explain Hopkinson’s test with its circuit diagram.

(15) State the various types of enclosures for rotating Electrical Machines and the type of cooling adopted in them.

(16) Explain different methods of drying out of Rotating Machine.

(17) Explain phase sequence test of synchronous Machines as per IS 7312: 1973.

(18) What is degree of protection? How it is designated? What is IP and IC code?

(19) Explain rating and estimation of rating of rotating electrical machines.

(20) State various troubles of DC motors, their causes and remedies.

(21) Explain alignment of Electrical Machines.

(22) Explain commissioning steps for synchronous machines.

(23) How the PI is measured of rotating machine? What is the significance of it on performance of rotating machine?

(24) Explain closing and opening mechanism in circuit breaker.

(25) Explain the working of ELCB? What are the different tests performed on it?

(26) Explain mechanical endurance test on circuit breaker.

(27) Explain any two routine test to be performed on circuit breaker.

(28) Which are different components of sub-station? What are the functions of each component in sub-station?

(29) Explain Murray loop test for ground fault location in underground cable.

(30) Explain Varley loop test for finding cable fault.

POWER SYSTEM PLANNING AND DESIGN (2180903)

ASSIGNMENT-1

1) Define Surge Impedance Loading. Explain the significance of it in Transmission Line Design.

2) Explain the factor consist for choice and spacing between conductor for transmission line design.

3) Explain corona effect and losses with standard formula.

4) Derive sag tension relation for span, width tower at each end located at equal level.

5) Explain the different types of extra high voltage tower.

6) What is the limitation of HVAC transmission line?

(7) Explain the use bundled conductors.

(8) Explain the insulation co-ordination.

ASSIGNMENT-2

(1) Explain the following distribution system with fig.

(1)Radial system (2) Parallel pr loop system (3) Network or grid system

(2) What is lamp flicker? What are its causes? What type of loads are

responsible for it ? how can it be reduced?

(3) Discuss Kelvin’s law the find the most economical conductor size.

what are the limitations of this law?

(4) State the different types of arrangements for distribution system and

also the advantages and disadvantages of radial secondary distribution system.

(5) Explain the lamp flickers, its causes and remedies.

(6) Discuss in details the steps in planning and designing electrical distribution schemes.

(7) List and explain the types of primary distribution system.

(8) Discuss briefly the design consideration in distribution system. Define and explain terms feeder, Discuss and service mains.

(9) Compare radial, rind and grid distribution system. State their

application.

10) Discuss classification of distribution system with neat diagrams. What are the advantages and dis-advantages of each?

Ex-1 A Single phase a.c, distributor 500m long has a total loop impedance of (0.02+j0.04) and is fed from one end at 250V.If is loaded as under (1) 50A at unity power factor ,200m from the feeding point.(2)100A at 0.8 power factor lag.300m from the feeding point.(3)50 A at 0.6 power factor lag, at the far end.

First Method

Current in section AD (Fig.)

for sum of the three load currents.

∴ current in AD

= 50 + 100 (0.8 − j 0.6) + 50 (0.6 − j 0.8)

= 160 − j100

Impedance of section AD

= (200/500) (0.02 + j 0.04)

= (0.008 + j 0.016) W

Second Method

We will split the currents into their active and reactive components as under :

50 × 1 = 50 A ; 100 × 0.8 = 80 A; 50 × 0.6 = 30 A

These are shown in(a). The reactive or wattless components are

50 × 0 = 0 ; 100 × 0.6 = 60 A ; 50 × 0.8 = 40 A

These are shown in Fig.(b). The resistances and reactances are shown in their respective figures.

Drops due to active components of currents are given by taking moments

= 50 × 0.008 + 80 × 0.012 + 30 × 0.02 = 1.96 V

Drops due to reactive components

= 60 × 0.024 + 40 × 0.04 = 3.04 Total drop = 1.96 + 3.04 = 5 V

This is approximately the same as before.

Third Method

The centre of gravity (C.G.) of the load is at the following distance from the feeding end

Ex-2 A 3 core distribution cable is 300m long and supplies a load of 100 KW at 440 volts at 0.9 p.f. lag for 3000hours in a year. T unit and he cable cost including installation is rs(13a +32)per meter where “a” is the cross section area of each conductor in sq. cm. cost of energy wasted is 12paisa per unit and the rate of interest and depreciation is 15%. The resistance per km of the conductor of 1cm2 cross-section is 0.213ohm. Find the most economical cross-section of the distributor cable.

Ex-3 A 2 wire dc distributor AB is 300m long and is fed at both the ends A and B .The distributor supplies a uniformly distributed load of 0.25A/m and concentrated loads of 40A at C and 60 A at D. The distance AC and BD are 120m each. The loop resistance of the distributor is 0.1 ohm/100m. Both A and B are maintained at 300V. Find the currents fed at A and B and the potential at point C and D.