DETECTION OF TAMPERING OF KILOWATT-HOUR METERS FOR MEASURING ELECTRICAL ENERGY CONSUMPTION

摘要

-19-ABSTRACT OF THE DISCLOSURETo detect tampering of a kilowatt-hour meterby the connection of a bypass link across the liveconnection through the meter, a voltage transformerwithin the meter unit is coupled to this live connectionso that a small voltage is induced in the live connectionin opposition to the supply voltage. The inducedvoltage produces a circulating current in the loopformed by the live connection and the bypass linkand the transformer coupling is such that, with abypass link of negligible resistance, the total current inthe live connection is in opposite phase to the appliedvoltage. By means of a current transformer,a logicunit and a microprocessor, the phase of the current inthe live connection within the meter is determined andis indicated by a latched flag indicator and/or transmitted toa distant data processor by a data link. Using a secondcurrent transformer in the return supply lead, the supplyand return currents in the leads within the meter unitcan be compared in the logic unit and processor to determine ifthe live connection is broken within the bypassed length.By means of contacts on the housing, indication is givenif the housing of the unit has been opened.