A rare event I'm told. Pole-mounted utility transformer cross-arm somehow detached on one end, fell to direct contact with house messenger (neutral) wire, energizing the main panel momentarily with primary voltage, 7200VAC. Substation relay tripped and denergised, but not before the main panel bussing melted at the far end & blew an oxy-acetylene-like hole in the back of the panel.
I've changed the panel & utility has reconnected, but I've not yet re-energised the branch circuits. My project is how to verify the house branch-circuit wiring. Examination in outlet boxes shows no visible damage or deterioration of insulation or conductors. I know resistance heating damage often shows up at terminations, but this may be different. My thought is to simply test the de-energised circuits end to end for unexpected resistances using a quality ohmmeter. I don't believe a megaohmmeter should be necessary as expected resistance is small. Would be nice if the whole house didn't have to be re-wired.
I've changed the panel & utility has reconnected, but I've not yet re-energised the branch circuits. My project is how to verify the house branch-circuit wiring. Examination in outlet boxes shows no visible damage or deterioration of insulation or conductors. I know resistance heating damage often shows up at terminations, but this may be different. My thought is to simply test the de-energised circuits end to end for unexpected resistances using a quality ohmmeter. I don't believe a megaohmmeter should be necessary as expected resistance is small. Would be nice if the whole house didn't have to be re-wired.
