The megger insulation tester is essentially a high range resistance meter.
Cable insulation test voltage.
After the connections are made the test voltage is applied and the ir is read at two different times.
The test is very sensitive to contamination in the assembly process.
Visual and mechanical inspection 2.
Usually either 30 and 60 sec or 60 sec and 10 min.
That this document list how to test specific pieces of equipment or systems.
The megger insulation tester is a small portable instrument that gives you a direct reading of insulation resistance in ohms or megohms.
If the high voltage test is made in ac it is then this is then more stressful for the sample and made according to the sketch below.
The first thing to check is the cable testing environment and cable preparation.
Within those sections there are typically three main bodies of information.
If the cable does not pass if a cable does not pass the test the cable still may be good but additional cable evaluation should be per formed.
The reasoning is that the low energy failure of the cable under test results in less collateral damage and a reduced likelihood of unplanned outages due to in.
The applied test voltage is raised in steps with measurements first taken up to 1uo or normal line to ground operating voltage.
Solder flux oils mold release agents and skin oil can cause problems.
Expected test results section 7 consists of sections specific to each particular type of equipment.
The results obtained from ir test are not intended to be useful in finding localized defects in the insulation as in a true hipot test but rather give information on the quality of the bulk material used as the insulation.
This means that they have a full rated insulation system which will consist of insulation semi con layers and a metallic shield.
Vlf tests at ieee 400 2 test levels do not damage cable systems good insulation but are used to degrade existing insulation defects to failure during the test rather than in service.
This test recognizes the fact that good insulation will show a gradually increasing ir after the test voltage is applied.
The insulation condition from values that are only relative.
A high voltage cable hv cable is a cable used for electric power transmission at high voltage a cable includes a conductor and insulation cables are considered to be fully insulated.
The insulation resistance test is typically done on every cable tested and usually done at 300 to 500 vdc with 100 to 500 megaohms resistance.
For good insulation the resistance usually reads in the megohm range.
Comparing this result with the correct row of table 2 shows that our cable passes the insulation resistance test.
This test doesn t significantly degrade the cable.
The high voltage test also called dielectric strength test or hipot test can be made in ac or dc.
If the tan delta numbers indicate good cable insulation the test voltage is raised up to 1 5 2uo.
