METHOD AND APPARATUS FOR DIGITALLY MEASURING ELECTRICAL ENERGY CONSUMPTION

摘要

A method and apparatus for digitally measuring electrical energyconsumption from a transmission line carrying alternating current. Instead ofactually measuring current from a transmission line conductor, the timederivative of the magnetic field induced by current flowing in the conductoris measured thereby obtaining a reading which is proportional to the timederivative of the current flow. Using an appropriate microcomputer, the timederivative of the magnetic field (the magnetic field rate of change) isrepresented with an algorithmic series for expressing cyclic phenomena, suchas the Fourier series of low order. An approximation of the power consumptionis then computed by converting the time derivative of the current as expressedin the algorithmic series and a voltage measurement from the conductormathematically to a power reading, and the power reading is summed to obtaina number value proportional to the energy consumption. Even harmonics andhigh frequency harmonics may be eliminated in the algorithmic expression ofthe current derivative to further simplify computer computations and requiredhardware, and the magnetic rate of change pickup and the voltage pickup arepreferably filtered to remove unwanted noise.