How do I to test underground wire?

[tommu56]

After the megger I'd put a full load or close to the wire current rating for 1/2 hour and check the voltage drop with the load on the wire.
Then remeg it again disconnected from every thing.
The reason it might not be grounded shorted but have been pulled thin and and cant carry the load.

 

[EE_Bota]

Electric fence energizer might also detect insulation flaws...the underground snapping sound tells me that a leak in my buried supply wire is the reason the fence isn't working right!
I'm not sure if 5k volts or so would damage intact insulation in a regular 220V wire, though.
Its a great time to have an electrician friend!
BOB

I would not do this. Household wiring rated for 220V service is a known fail against a fence charger. None will handle the 6000V spikes for long, and blasting arcs through the insulation ruins the insulation. If you look at the wire for fence lead burial, it is rated for 20,000 volts.

Some fences are long enough to exhibit transmission line characteristics. The FAQ at the Gallagher charger site mentions many of these things.