Megger Test (Insulation Resistance Test)
A Megger test measures the insulation resistance of the electrical equipment & wiring.
It helps keep insulation in good condition & prevents electrical leaks or short circuits.
Why is the Megger Test used?
1). Detect Insulation Weakness: Identifies insulation degradation caused by aging, moisture, or damage.
2). Prevent Electrical Failures: Assists in avoiding short circuits and electrical risks.
3). Ensure Safety: Confirms that the insulation can withstand voltage stress without leakage.
4). Compliance with Standards: Ensures that equipment complies with safety regulations.
How does Megger Test Work?
A Megger (Megohmmeter) provides a high DC voltage (500V, 1000V, or higher) to the insulation.
It measures the resistance (in MΩ) between conductors & the ground (or) between phases.
High resistance implies good insulation, whereas low resistance suggests insulation failure.
How to Perform a Megger Test?
1). Turn off the power and ensure the circuit is get de-energized.
2). Connect the Megger. One lead goes to the conductor. The other lead connects to the earth or another conductor.
3). Use Test Voltage - Determine the suitable voltage depending on system needs.
4). Measure Insulation Resistance - Check the figure on the Megger display.
5). Interpret the results.
- Above 1 ΜΩ indicates good insulation.
- Between 0.1 ΜΩ and 1 ΜΩ, there is a warning of probable degradation.
- Insulation failure occurs below 0.1 ΜΩ and requires prompt action.
Applications of the Megger Test
- Power cables
- Motors & Generators
- Transformers
- Switchgear and control panels