Testing for External Earth Fault Loop Impedance (Ze) When You Have a Main Earthing Terminal (MET) Live testing for external earth fault loop impedance often called the Ze test. This test is demonstrated on a live 3 phase distribution board and will help with AM2, AM2S and AM2E exams. In this video I show you the importance of removing parallel earth paths and how this can be achieved when an installation has a remote MET (main earth terminal). As always preparing for your end skills test AM2, AM