Detection of tampering of kilowatt-hour meters for measuring electrical energy consumption

摘要

To detect tampering of a kilowatt-hour meter by the connection of a bypass link across the live connection through the meter, a voltage transformer within the meter unit is coupled to this live connecton so that a small volage is induced in the live connection in opposition to the supply voltage. The induced voltage produces a circulating current in the loop formed by the live connection and the bypass link and the transformer coupling is such that, with a bypass link of negligible resistance, the total current in the live connection is in opposite phase to the applied voltage. By means of a current transformer, a logic unit and a microprocessor, the phase of the current in the live connection within the meter is determined and is indicated by a latched flag indicator and/or transmitted to a distant data processor by a data link. Using a second current transformer in the return supply lead, the supply and return currents in the leads within the meter unit can be compared in the logic unit and processor to determine if the live connection is broken within the bypassed length. By means of contacts on the housing, indication is given if the housing of the unit has been opened.