What is the minimum acceptable value of insulation resistance?
The rule may be stated: 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.
Uses of Megger. The device enable us to measure electrical leakage in wire, results are very reliable as we shall be passing electric current through device while we are testing. The equipment basically use for verifying the electrical insulation level of any device such as motor, cable, generator winding, etc.
- As you know good insulation has high resistance and poor insulation relatively low resistance. The Megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. For good insulation, the resistance usually reads in the megohm range.
- The megger is a device which is used to measure higher values of resistance. We uses megger to measure insulation resistance of electrical machines and cables. By measuring the insulation resistance we can find the health of insulation.
- The following is a summary of insulation resistance (IR) testing (commonly referred to as “megger testing”) of low voltage cables (rated less than 5 kV), recognized by Nexans. Cable end condition (i.e. insulation not stripped back, cable ends not separated).
Megger is a measuring instrument used for the measurement of insulation resistance of an electrical system. An electrical system degrades its quality of insulation resistance with time and various environmental conditions including temperature, moisture, dust particles & humidity.
- Insulating oil in an electrical power transformer is commonly known as Transformer Oil. It is normally obtained by fractional distillation and subsequent treatment of crude petroleum. That is why this oil is also known as Mineral Insulating Oil. Originally Answered: What is the scientific name of transformer oil?
- Polychlorinated biphenyls (PCBs) are synthetic chemicals which are no longer produced in the United States, but are still found in the environment. PCBs have been used as coolants and lubricants in transformers, capacitors, and other electrical equipment because they don't burn easily and are good insulators.
- PCBs have been used as coolants and lubricants in transformers, capacitors, and other electrical equipment because they don't burn easily and are good insulators. The manufacture of PCBs was stopped in the U.S. in 1977 because of evidence they build up in the environment and can cause harmful health effects.
The reason a multimeter cannot measure such extremely high resistance is because the measurement is performed with a low voltage (often a 9V battery inside the multimeter). It does mean that an insulation resistance meter should not be used on electronic circuits.
- Use the Megger probes to test insulation resistance.
- Switch off power to the circuits you are testing.
- Prepare a table in which you can record the insulation values that result from your tests.
- Select 500 volts DC or 1000 volts DC as the test voltage on your Megger, depending on the model you are using.
- Megger is a measuring instrument used for the measurement of insulation resistance of an electrical system. An electrical system degrades its quality of insulation resistance with time and various environmental conditions including temperature, moisture, dust particles & humidity.
- 1. IR Values For Electrical Apparatus & Systems
Max.Voltage Rating Of Equipment Megger Size Min.IR Value 250 Volts 500 Volts 25 MΩ 600 Volts 1,000 Volts 100 MΩ 5 KV 2,500 Volts 1,000 MΩ 8 KV 2,500 Volts 2,000 MΩ
Updated: 2nd October 2019