Wiring Schematic diagram

In this article we will go through Megger test first of all i want to say both insulating
resistance tests and megger test are same. which is usually carries out to find the insulation
of different machines windings conductor wires generator windings etc.
Megger Testing Instrument
Megger testing instrument is a high resistance Ohmmeter with a build in
generator


It is equipped with three connections Line Terminal (L), Earth Terminal (E) and
Guard Terminal (G)
Resistance is measured between the Line and Earth terminals
The “Guard” terminal is provided for special testing situations where one
resistance must be isolated from another.
The generator can be hand-cranked or line-operated to develop a high DC
voltage which causes a small current through and over surfaces of the
insulation being tested
Which is measured by an ohm meter having an indicator scale
Importance Of Insulation Resistance Test Or Megger Test
An insulation test is carried out to test the integrity of the insulation between
conductors.
Which help to find the short schema problems in the schema
It also serves as the best guide to indicate the health of the equipment
Procedure To tests the Insulation
Test the megger before use, whether it gives INFINITY value when not
connected, and ZERO when the two terminals are connected together and the
handle is rotated.
To do the test you ensure the cable is disconnected from any devices (megger
normally work on 500v, 1000v testers for higher voltage testing).
Make sure that no eddy current in the device by earthing it.(very important)
Instrument should be in normal working temperature because resistance is
related to temperature.
Ensure both ends of the cables are separated from each other (connect one end
in terminal strip if necessary).
Now connect the megger terminals to the conductors which has to be meassured
Then hand crank the generator and a high DC voltage generated which causes a
small current through and over surfaces of the insulation being tested.
If the Reading shows Infinity means the conductors having good insulation.
Here it shows a megger schema diagram
Image credits:tpub.com,electrical-engineering-portal.com
Bijoy