What are the causes of insulation failure?
Main Reasons for Insulation Failure
- Natural deterioration due to aging.
- Accelerated by excessive heat and moisture.
- Heat, moisture and dirt are main causes of insulation failure.
- Chemical deterioration.
- Mechanical damage.
- Sunlight.
- Excessive voltage stresses.
What is insulation degradation?
Abstract: An avalanche of physical and physicochemical phenomena, often self-sustained, leads to the end of life of an insulating material. The collapse of the insulating role of a material is mostly due to the electrical field stress.
What happens if insulation degradation goes undetected?
This deterioration can result in dangerous conditions in power reliability and personnel safety. As such, it’s important to identify this deterioration quickly so that corrective steps can be taken.
What causes low insulation resistance?
Low insulation resistance may be due to the age of the installation, or alternatively it may be caused by an individual circuit, which would merit further investigation. In summary, insulation resistance testing should be undertaken at relevant times during and on completion of an installation.
What is the minimum acceptable insulation resistance?
Insulation resistance should be approximately one megohm for each 1,000 volts of operating voltage, with a minimum value of one megohm. For example, a motor rated at 2,400 volts should have a minimum insulation resistance of 2.4 megohms.
Can a Megger damage insulation?
Using a megger meter is not destructive. When insulation has been damaged, a megger tester is used in determining the cause by testing. The test is typically conducted at rates that are low as compared to the insulation. The insulation tests may range from as low as 40 V dc to 10 kV.
Why Megger is used instead of multimeter for insulation testing?
Megohmmeters provide a quick and easy way to determine the condition of the insulation on wire, generators, and motor windings. A megohmmeter is an electric meter that measures very high resistance values by sending a high voltage signal into the object being tested.
How do you test for insulation resistance?
Insulation resistance measurement is done using an IR tester. This is a portable tool that is more or less an ohmmeter with a built in generator that’s used to produce a high DC voltage. The voltage usually measures at least 500V, and causes a current to flow around the surface of the insulation.
How much voltage does a Megger put out?
Working Principle of Megger Test 500 Volt DC is sufficient for performing test on equipment range up to 440 Volts. 1000 V to 5000 V is used for testing for high voltage electrical systems.
Can you Megger a DC motor?
The megger tester uses a high voltage, generally in the 1000 to 10,000 volt range to identify insulation leakage in motor coils and adjacent wiring. By following a basic setup you can test a DC motor using this high voltage testing device.