Mike & LK, I agree a megger is a very useful tool to own. On Sunday myself and another electrician will be testing the secondary conductors on a 3000 amp 480/277 underground service. We will be using a megger to do insulation resistance tests on each conductor. The facility we are testing at checks their underground cables yearly. Test results can be compared from previous years to see if the insulation is breaking down.
A good 73 page booklet on the use of Meggers is "A stitch in time" the complete guide to insulation testing. It is available at
www.megger.com .
