Why Do We Measure Only Insulation Resistance Using aMmegger ??

Does insulation, by itself, even have inductance or capacitance?

if capacitance can exist between power lines and earth and inductance can exist on transmission lines then why can inductance or capacitance be present in insulations

<sigh> Why would one need to know?

OP

why do we use only insulation resistance in megger why not insulation reactance due inductance or capacitance..............and why only dc current is injected in a megger

A megger is used and to find out what and why? will answer your question, both the parts.

KS- I don't know why you have put your post OT. Only the inadvertent error that has cropped in is

DC cables currents have no such limitation, and are essentially bound by only Ohm's Law

Welcome from an old inhabitant. Sorry i didn't see you are greenhorn here .

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This post is OT but I am keeping it on so that you may see how the OT system works.

Simply because even you can measure capacitance/inductance/reactance of insulation, the values are not significant at all in electrical power distribution.

Megger meter applies voltage , not current, but read current to give ohmic value.