What is megger and how does it work?

Answer 1

Purpose: The megger tests the integrity of the insulation between conductors that run side by side and do not physically meet or connect. Meggers or Mega-ohm testers also are typically used to test the dielectric in coaxial cable. Meggers are used to test the insulation of buried cables by placing a lead to earth ground and one lead to the outer conductor of a coax cable or any or all conductors of multiple (more than one) buried wires. Method: introduce a high enough voltage to the conductors eventually the current will travel betwen the conductors. Read the indicator to see the amount of resistence to current flow on the meter indicator. the reading will generally be in millions of Ohms (megohms)

Answer 2

MEGGER

Megger is the portable insulation tester. It is used to remove very high resistance of the order of mega ohms.

PRINCIPLE

The instrument works on the principle of ratio-meter/ohmmeter.The required deflection torque is produce by both voltage and current.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.

WORKING

Resistance to be measured is connected across the test terminals i.e. connected in series with the deflecting coil and across the generator.When current are supplied to the coils then they have torque in opposite direction.

• If the resistance to be measured is high,no current is flowing through the deflecting coil.The controlling coil will therefore ,set itself perpendicular to the magnetic axis and hence,set the pointer at infinity.
• If the resistance to be measured is small,a high current is flowing through the deflecting coil and the resulting torque sets the pointer to zero.
• For intermediate values of resistances,depending upon the torque production,the pointer is set at a point between zero and infinity.
• The hand driven generator is of permanent magnet type and it is designed to generate from 500V to 2500V.

Answer 3

What does a megger do ?

Megger is an instrument used to measure Insulation Resistance of cables, power system devices.