What is the Measurement of Insulation Resistance?

What is the Measurement of Insulation Resistance?

Insulation Resistance Definition

Insulation resistance is defined as the ratio of applied direct voltage across an insulation to the current through it.

Importance of Measurement

• Direct-indicating ohmmeter with hand driven dc generator. This is locally known as hand driven megger since Megger is one of the best known manufacturer of this instrument.

• Direct-indicating ohmmeter with motor driven dc generator. This is locally known as motorized megger.

• Direct-indicating ohmmeter with self-contained battery.

• Direct-indicating ohmmeter with self-contained rectifier. This instrument takes power from an external AC supply.

• Resistance bridge circuit with self-contained galvanometer and battery.

• Current Components

The current during insulation resistance measurement includes surface leakage current and volume current, with the latter having three parts: capacitive charging current, absorption current, and conduction current.

Measurement Methods

Insulation resistance can be measured using various methods, including direct-indicating ohmmeters and resistance bridges.

Instruments

Common instruments for measuring insulation resistance include hand-driven ohmmeters, motorized ohmmeters, and devices with built-in batteries or rectifiers.