E AND EM

PRESENTATION ON

MEGGER

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PRESENTED BY:-1.JOYDEEP MODAK2.SAURAV JYOTI HAZARIKA3.KAUSIK DAS4.DIPJYOTI5.ANKUR6.RISHIRAJ

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CONTENTS:-

1. INTRODUCTION

2. HISTORY

3. FEATURES

4. PRINCIPLE

5. CONSTRUCTION

6. ADVANTAGE

7. ERRORS

8. APPLICATION

9. CONCLUSION

INTRODUCTIONMEGGER The megger , or megohmmeter , is a high range ohmmeter. Used to measure insulation resistance and other high resistance values.

This principle forms the basis of insulation testing instrument known as MEGGER. Also used for ground, continuity, and short circuit testing of electrical power systems. Designed to cover a wide range(more than 1000megohms) of resistances.

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HISTORYMegger Instruments Limited was based at AVO’s Dover site, in Archcliffe Road, Dover, CT17 9EN, Kent, England, which is also the present location of the UK branch of the company.In 1991, due to the popularity of the AVO products the company changed the name to AVO( Multimeter with Amps, Volts and Ohms) Megger Instruments Limited. In 2000 the company became known as AVO International Holdings Limited and in 2002 as AVO International Limited.Finally the whole Megger group changed its name to Megger Group Limited in 2002, as it is known today.Megger Group Limited is a company that manufactures electric test equipment and measuring instruments for electrical power applicationsThe Dover site employs around 230 people. In total (including the sales channels) Megger Group Limited employs around 1500 people worldwide.

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FEATURES:• Storage of test results.• Recall of test results to instrument display.• Connect to IBM compatible PC forstorage of results.• Variable RCD test current forprogrammable devices.• Designed and manufactured inaccordance with International SafetyStandards.• Continuity tests with 200 mA shortcircuit capability.• Prospective Earth Fault and ShortCircuit Current.

• Supply voltage, polarity andfrequency indication.

• Complete with Carry Case, TestLeads and Certificate of Test.

PRINCIPLE :

The instrument works on the principle of ratio-meter/ohmmeter . The required deflection torque is produce by both voltage and current(in the cross-coil) . Due to the interaction between the magnetic field produce by voltage and current , the deflecting torque is produce . The required coil are so positioned that the deflecting torque is proportional to the ratio V/I.

*Torque of coil A proportional to I1 cos Ө

*Torque of coil B proportional to I2 cos(90- )Ө

there for,

I1 cos Ө = I2 cos (90- )Ө

I1 cos Ө = I2 sin Ө

Tan Ө = I1/I2 which is equal to R/R1

*If R1 fixed then the scale calibrated R directly.*The two coil comes in position of equilibrium when two torque equal.

CONSTRUCTION OF MEGGER

ADVANTAGES OF MEGGER

Permanent magnet DC generator

Measures resistance between zero to infinity

• Permanent magnet DC generator: The megger has a small permanent magnet DC generator. The generator is capable of generating either 250V or 500V at full speed. This generator generates a constant voltage and thus avoids the effect of capacitive currents.

• Measures resistance between zero to infinity: A megger can measure all resistance lying between zero and infinity essentially it is a high resistance measuring device.

• ERRORS READING VALUE DUE TO LOW BATTERY

• ERRORS DUE TO CHANGE IN TEMPERATURE

• ERRORS DUE TO SENSITIVITY

• ERRORS DUE TO CHANGE IN HIGH VOLTAGE

SETTING

ERRORS OF MEGGER

1.Measurement of high value resistances.

2.Used to measure the electrical resistance of insulators.

3.Testing of electrical components, machinery.

4.Installations for winding

APPLICATIONS OF MEGGER

CONCLUSION• Megger is a VERY USEFUL INSTRUMENT which is use to determine all the resistances

between Zero and Infinity.

• Actually zero is the 1st mark and 10k ohm is the 2nd mark so it is impossible to accurately measure small resistances with the help of a Megger

• This instrument is very simple to operate, portable and independent of the external supplies.

REFERENCE• A text Book of Electrical Technology By B.L. THERAJA

• Electrical and Electronic Measurements And Instrumentation By A.K.Sawhney

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