A zero mega-ohm reading on a megger indicates that the cable has a short circuit or insulation failure, making it unsafe for use in electrical applications. To potentially reuse the cable, you must first repair or replace any damaged sections and ensure proper insulation integrity. After repairs, retest the cable with the megger to confirm it meets the required insulation resistance standards before reinstallation. If the cable is beyond repair, it should be properly disposed of to prevent safety hazards.
On a megger device, 1 megaohm will typically be indicated on the display or dial as "1 MΩ" or "1.0 MΩ." Depending on the specific model, it may be shown as part of a range or scale that includes other resistance values. The reading will be steady if the insulation is good, and a higher reading indicates better insulation quality. If the reading fluctuates or shows a value significantly lower than 1 MΩ, it may indicate insulation problems.
Normally the megger should be selected based on the following criteria. 1.Voltage rating of the megger 2.Range of the megger value 3.Manual - Hand operated analogue type 4.Auto- Digital Megger To measure the insualtion resistance of Motor (LV Motors) Up to 500 V/1000 V Megger is sufficient To measure the insualtion resistance of Motor (HV Motors) Up to 5000 V can be choosen Normaly the range starts from 0.5 to Infinity meg value in the analogue However in digital the based on the least count /range of the instrument we can able to measure the insualtion value.
The typical test equipment for this is a megger. The megger is connected to two conductors at a time to test the insulation between the two.
For 600V insulation Megger NETA & IEEE recommends: Test voltage = 1000V Test Duration = 1 minute Test Value = 100 Megohm minimum (corrected to 20 degrees C) Typically you megger conductor to conductor and conductor to ground. Most will not megger for the full minute and it is up to your discretion. Just watch that the resistance continually increases during the test period. If it is decreasing then you should hold the full minute and investigate the reason. For multiple conductor cables then twist all of the conductors together and pull out one at a time and megger it to the bundle. This will expedite thetesting into as few as tests possible while still thoroughly checking the cable. Note that test voltage and values are based strictly on the insulation rating and the conductor size is pretty much irrelevent.
The main part of a megger, or insulation resistance tester, is its high-voltage generator, which produces a test voltage to measure the insulation resistance of electrical systems and components. It also includes a sensitive galvanometer or digital display to indicate the resistance value. Additionally, megger devices typically have test leads and terminals that connect to the circuit under test, allowing for accurate readings of insulation quality.
The megger value of a 33kV XLPE cable typically ranges from 1000 megohms (MΩ) to 5000 MΩ or higher, depending on the cable's condition and length. A megger test measures the insulation resistance, and values below this range may indicate insulation degradation or moisture ingress. Regular testing helps ensure the cable's reliability and safety in operation. Always consult the manufacturer's specifications for the most accurate benchmark values.
On a megger device, 1 megaohm will typically be indicated on the display or dial as "1 MΩ" or "1.0 MΩ." Depending on the specific model, it may be shown as part of a range or scale that includes other resistance values. The reading will be steady if the insulation is good, and a higher reading indicates better insulation quality. If the reading fluctuates or shows a value significantly lower than 1 MΩ, it may indicate insulation problems.
The value of insulation resistance varies according to the type of CT and manufacturer. It is best to check with the manufacturer for acceptable values. The word 'Megger' is a registered trademark of Megger Limited. Megger Limited's product range includes insulation testers, relay testers, battery testers and many other electrical test and measurement products. Tony Wills, Applications Engineer, Megger Ltd.
Normally the megger should be selected based on the following criteria. 1.Voltage rating of the megger 2.Range of the megger value 3.Manual - Hand operated analogue type 4.Auto- Digital Megger To measure the insualtion resistance of Motor (LV Motors) Up to 500 V/1000 V Megger is sufficient To measure the insualtion resistance of Motor (HV Motors) Up to 5000 V can be choosen Normaly the range starts from 0.5 to Infinity meg value in the analogue However in digital the based on the least count /range of the instrument we can able to measure the insualtion value.
The typical test equipment for this is a megger. The megger is connected to two conductors at a time to test the insulation between the two.
While using megger we only have to see whether resistance breaksdown at the upper value mentioned. Since megger generates high voltage we can check whether breakdown takes place or not.Megger has a range from o to infinity.So it is not possible to find accurate resistance,hence it is used as an insulation tester
we will get its insulation resistance value wchich should be greater than 200Mohms
For 600V insulation Megger NETA & IEEE recommends: Test voltage = 1000V Test Duration = 1 minute Test Value = 100 Megohm minimum (corrected to 20 degrees C) Typically you megger conductor to conductor and conductor to ground. Most will not megger for the full minute and it is up to your discretion. Just watch that the resistance continually increases during the test period. If it is decreasing then you should hold the full minute and investigate the reason. For multiple conductor cables then twist all of the conductors together and pull out one at a time and megger it to the bundle. This will expedite thetesting into as few as tests possible while still thoroughly checking the cable. Note that test voltage and values are based strictly on the insulation rating and the conductor size is pretty much irrelevent.
The main part of a megger, or insulation resistance tester, is its high-voltage generator, which produces a test voltage to measure the insulation resistance of electrical systems and components. It also includes a sensitive galvanometer or digital display to indicate the resistance value. Additionally, megger devices typically have test leads and terminals that connect to the circuit under test, allowing for accurate readings of insulation quality.
By Megger testing (meggering) of the motor any one can measure the IR of the motor. MEGGER is a device used to measure IR. Analog Megger device may generate 500 volts..it gives coil to coil or coil to body IR value...it should not be less than 2 Mega ohm, generally it should be or kept more than 5 mega ohm...thanks ...DEEPAK RAJPUT
[Your Company Letterhead] [Date] [Client's Name] [Client's Address] Subject: Megger Test Certification Dear [Client's Name], We hereby certify that a Megger Test was conducted on [specific equipment or installation] on [date] at [location]. The insulation resistance measured was [value] megohms, which meets/exceeds the required standards. This test ensures the safety and reliability of the electrical system. Sincerely, [Your Name] [Your Position] [Your Company] [Contact Information]
It checks resistance from a circuit or an electrical component to earth, to make sure it is electrically isolated. This must be a very high value of resistance, hence 'megohms'.