Question

a) Sketch the circuit diagram of an instrument for testing insulation resistance.

b) State the precautions to be observed when using the instrument described above.

Answer.

a) The sketch shows the circuit diagram for an insulation tester known as a meggar.

A hand driven generator gives a D.C. test voltage to operate the equipment.

b) Precautions to be taken when using the equipment or the insulation being tested are;

The supply to the equipment being tested must be isolated

When using the equipment, do not touch any of the components being tested.

Any insulation readings taken should be as high as possible, generally anything below 5 Megaohms should be investigated.

Lloyds work on a rule of 1 Megaohm / 1000 V