In this article, drying of switchgear is given by the Megger. The switchgear equipment is dried out before used in the system.

Insulation Resistance

A 1000 V megger is used for measurement of insulation resistance, for higher rating motorized megger of 2.5 kV shall be used.
The switchgear equipment first dried out before it is switched when

Insulation Resistance of switchgear

Insulation Resistance	Voltage Rating
< 1 Mega ohm	Rated 1000 V
100 Mega ohm	Rated voltage above 1000 V and up to including 33 kV
1000 Mega ohm	Rated voltage above 33 kV

Drying out of switchgear

It is noted that continuously apply heat for a considerable time so as to dry out moisture.
It is recommended to takes insulation resistance periodically during drying out period.
It is generally found that at the beginning of drying out, moisture is redistributed.
The value of insulation resistance becomes minimum after some time and stability this value for some time, after that its value increases and reaches its maximum value.
This value is generally much greater than value specified in above table.
The switchgear equipment is safer to put into service when the insulation resistance has been reached.