The megger insulation tester is a small portable instrument that gives you a direct reading of insulation resistance in ohms or megohms.
Insulation resistance test standard for cable.
Also acceptable values of insulation resistance depend upon the equipment you re testing.
The test measures the insu lation resistance between the phases and or between phase and ground.
Developed early in the 20th century the insulation resistance ir test is the oldest and most widely used test for assessing the quality of insulation.
Cables for rated voltages of 1 kv um 1 2 kv and 3 kv um 3 6 kv reference number.
Insulation resistance test data may be used to establish a trending pattern.
Regular testing of the insulation on an installation or machine is therefore a useful way of monitoring this type of deterioration so you can act before total failure occurs.
Historically many field electricians use the somewhat arbitrary standard of 1 megohm per kv.
Power cables with extruded insulation and their accessories for rated voltages from 1 kv um 1 2 kv up to 30 kv um 36 kv part 1.
When overpotential testing cable its common practice to conduct the insulation resistance measurement first and then proceed with the dc overpotential test if acceptable readings are achieved.
With a little record keeping and common sense however you can get a good picture of the insulation condition from values that are only relative.
For cables rated 600 v the minimum acceptable insulation resistance values for cable lengths from 100 to 1000 feet would be as shown in the following table from ieee 525.
If insulation resistance of the cable is found between 1000 and 100 kω km at buried temperature the subject cable should be replaced urgently within a year.
Insulation resistance testing purpose.
The insulation resistance test is the second test required by the electrical safety testing standards.
The international electrical testing association neta specification maintenance testing specifications for electrical power distribution equipment and.
Principle of insulation testing and influencing factors insulation resistance measurement is based on ohm s law.
Deviations from the baseline information permit evaluation of the insulation.
The insulation resistance test consists in measuring the insulation resistance of a.
If during periodical testing insulation resistance of cable is found between 5 and 1 mω km at buried temperature the subject cable should be programmed for replacement.
Minimum acceptable insulation resistance for 600 v cable from 100 to 1000 feet.
After dc overpotential test is completed the insulation resistance test is done again to assure that the cable has not been damaged by the hi pot.
It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs.
Insulation resistance decreases in temperature or moisture.
