What type of electrical current does a megger measure?

A megger, which is short for insulation resistance tester, is specifically designed to measure the insulation resistance of electrical systems. It does this by generating a high DC voltage and measuring the resistance offered by the insulation material. This is essential for assessing the condition of insulation in cables and equipment, as good insulation will have a high resistance, indicating that it is effectively preventing leakage current.

The reason insulation resistance is measured using a megger stems from the fact that high voltage DC can more effectively stress the insulation and reveal any weaknesses. The reading indicates how well the insulation is performing and helps to ensure safety by preventing potential electrical faults, which could lead to equipment damage or electrical shock hazards.

Unlike AC or DC current measurements, which evaluate the flow of current in a circuit, the focus of a megger is specifically on the resistance provided by insulation. Therefore, it is vital for predictive maintenance and ensuring compliance with safety standards in electrical installations.