What are acceptable Megger test readings?
What are acceptable Megger test readings?
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.
What voltage should I megger at?
Voltage for testing produced by hand operated megger test by rotation of crank in case of hand operated type, a battery is used for electronic tester. 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.
How do I know the megger value of cable?
Connect conductor under test to the Line terminal of the megger. Connect earth terminal of the megger to the earth. Rotate the handle of megger or press push button of megger. The reading of meter will show the insulation resistance of the conductors.
What is a good Megger test result?
Turn on and read the meter. Anything reading between 2 megohms and 1000 megohms is usually considered a good reading, unless other problems have been noted. Anything less than 2 megohms indicates an insulation problem.
What is a bad reading on a Megger?
What is a bad reading on a Megger test? If the megger reads a resistance under 1 (1,000 ohms) on your meter after the initial 60-second interval, the cable has failed and the cable should be removed. If the megger reads a resistance between 1-1.25 on your meter, then the cable passes.
What is infinity on a Megger?
If your megohmmeter is reading “OL” (over load) or “I” (infinity), these are commonly used readings on megohmmeters when the measurement exceeds the maximum indicated value of the tester.
What is a bad insulation resistance reading?
The purpose of the IR test is to check for damaged insulation, this can be mechanical damage or damage by heat, (overloaded cables), readings less than 2 Mohm indicate damaged insulation, readings of 2-50 Mohm are indicative of long circuit lengths, moisture and contamination and do not indicate the insulation quality.
How do you calculate insulation resistance?
How is insulation resistance calculated and tested? We should all be familiar with Ohm’s law. If we apply a voltage across a resistor and then measured the consequential current flow, we can then use the formula R=U/I, (where U=Voltage, I=Current and R=Resistance) to calculate the resistance of the insulation.
What is the minimum acceptable value of cable 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.
What is the minimum Megger value?
(1) IR Values For Electrical Apparatus & Systems:
| Max.Voltage Rating Of Equipment | Megger Size | Min.IR Value |
|---|---|---|
| 600 Volts | 1,000 Volts | 100 MΩ |
| 5 KV | 2,500 Volts | 1,000 MΩ |
| 8 KV | 2,500 Volts | 2,000 MΩ |
| 15 KV | 2,500 Volts | 5,000 MΩ |
What is the minimum acceptable insulation resistance allowed?
Can a megger damage a motor?
Never use a megger if the motor windings are under a vacuum. A high voltage for too long of a time may further weaken or fail motor windings and the winding insulation could be damaged by the testing procedure.
How do you test a cable with a Megger?
To test a cable with a megger, you connect one probe to the outside of the cable and, with the power turned off, you touch the probe to the conducting wire at the point of connection. A megger is an ohmmeter that measures resistance in the megohm scale.
What’s the highest voltage Megger you can get?
The highest voltage megger I have seen was 2500 volts. Standard seems to be 500/1000 volts. Hi-pot sets start at about 1000 volts and go up from there. I would check with cable supplier before hi-potting any cable in the field.
How many volts are in a 15kv cable?
20 Apr 06 11:29 According to Okonite’s guide, it’s 300 volts per mil, so at 15kV class for acceptance testing: 100% (175 mil) = 55kV 133% (220 mil) = 65kV
When did Megger 10 kV insulation resistance tester come out?
Megger developed a 10 kV unit to meet the new testing recommendations outlined by the IEEE. Megger has offered a 10 kV insulation resistance tester since 2001. In March 2000, The IEEE-SA Standards Board approved a revision to IEEE Std 43-1974.