Patent ID: 8379355
Filing Date: 2013-02-19
Classification: G01R

Abstract:
1. A method for detecting the presence of an unsafe condition at a power metering device, said power metering device interposed between a voltage source and a load, said power metering device connecting to said voltage source at a first source contact and a second source contact, and said power metering device connecting to said load at a first load contact and a second load contact, said power metering device having a disconnect switch, said disconnect switch having an open position, said disconnect switch disabling power from flowing through said power metering device from the voltage source to the load when the disconnect switch is in the open position, the method comprising: determining if the disconnect switch is in the open position, measuring a first voltage at said first load contact with respect to a non-zero alternating current (AC) voltage at one of said source contacts; measuring a second voltage at said second load contact with respect to the non-zero AC voltage at said one of said source contacts; determining if the first voltage is greater than a first voltage threshold or less than a second voltage threshold; determining if the second voltage is greater than the first voltage threshold or less than the second voltage threshold; indicating that an unsafe condition exists if either: a) the first voltage is greater than the first voltage threshold; or, b) the second voltage is less than the second voltage threshold; or, c) the second voltage is greater than the first voltage threshold; or d) the first voltage is less than the second voltage threshold; and, the disconnect switch is in the open position.