Why we use MV-cable with 133% insulation level for ungrounded systems and 100% insulation level for grounded systems? what is the main different with their application?Thanks
Why we use MV-cable with 133% insulation level for ungrounded systems and 100% insulation level for grounded systems? what is the main different with their application?Thanks
If I remember correctly I think the difference in application has to do with the time it takes to clear a ground fault on the system. The 100% insulation level cable is typically used on grounded systems where the fault will be cleared within 1 minute and the 133% is is used on ungrounded systems where the clearing time does not exceed 1 hour. This does not keep you from using the 133% where you would like the higher insulation level.
