5 Things to Know About Megger Testing Extension Cords at 500V

Test only with the cord completely unplugged from power and any load. If the cord has molded ends, access conductors at a damaged cut or carefully probe the prongs.

Connect one megger lead to a conductor (hot, neutral, or ground) and the other to a different conductor or the outer jacket. Press test to apply 500V or 1000V and read insulation resistance in megohms.

Anything above 1 MΩ is technically passable, but a healthy cord should show 100 MΩ or more. Below 1 MΩ means toss or repair the cord.

Moisture in the cord will ruin the reading, so test it dry. Wet cords often show falsely low resistance.

Do not touch bare wires during testing. 500V is unlikely to kill you, but it will deliver a painful shock.